Small Bowel Cancer
Small bowel adenocarcinoma and lymphoma
DefinitionClick to collapse
Small bowel adenocarcinoma (SBA) is a malignant epithelial neoplasm arising from the glandular mucosa of the small intestine, encompassing the duodenum (derived from the foregut/midgut), jejunum, and ileum (both midgut). Anatomically, the small bowel extends from the pylorus to the ileocecal valve. SBA accounts for an estimated 30% to 40% of all small intestinal cancer diagnoses, with neuroendocrine tumors, gastrointestinal stromal tumors (GISTs), and lymphomas comprising the other major histologies [4]. The clinical definition is based on pathologic confirmation of adenocarcinoma in one of these segments, with staging according to the AJCC 8th edition TNM system for small intestine adenocarcinoma [6]. SBA is a rare malignancy: in 2024, an estimated 12,440 new cases of small bowel cancer were projected in the United States, with approximately 2090 deaths [1]. The disease is often diagnosed at an advanced stage due to nonspecific presenting symptoms such as gastric outlet obstruction (duodenal tumors), cramping abdominal pain (jejunal/ileal tumors), or occult gastrointestinal bleeding [36,41,42]. For duodenal primaries, discrimination from ampullary, distal common bile duct, or pancreatic head malignancies is required; the epicenter of the tumor or precursor lesion should not be at the ampulla, and >75% of the mass should not be within the ampulla [SBA-B]. Regional lymph nodes differ by primary site: for duodenum, nodes include retropancreatic, hepatic artery, inferior pancreaticoduodenal, and superior mesenteric; for jejunum/ileum, nodes include cecal (terminal ileum only), ileocolic (terminal ileum only), superior mesenteric, mesenteric, and NOS [SBA-B]. The NCCN Guidelines define distinct clinical pathways for duodenal versus jejunal/ileal primaries and for mismatch repair proficient (pMMR)/microsatellite stable (MSS) versus deficient MMR (dMMR)/MSI-high (MSI-H) or POLE/POLD1 ultra-hypermutated phenotypes [SBA-2 through SBA-5].
EpidemiologyClick to collapse
SubtypesClick to collapse
Duodenal Adenocarcinoma
Adenocarcinoma arising in the duodenum, the most common subsite, accounting for approximately 52% to 58% of all SBA cases [36-39]. These tumors often present with gastric outlet obstruction or jaundice and require careful distinction from ampullary, biliary, or pancreatic primaries via endoscopic ultrasound (EUS) [SBA-A]. Surgical management typically involves pancreaticoduodenectomy (Whipple procedure) for tumors in the second portion or invading the ampulla/pancreas; limited segmentectomy may be considered for anti-mesenteric lesions in the third/fourth segments [SBA-C].
Jejunal Adenocarcinoma
Adenocarcinoma arising in the jejunum, the second most common subsite. These tumors often present with cramping abdominal pain or obstruction. Surgical management is segmental resection with margins of at least 5–10 cm and lymph node dissection to the origin of feeder vessels [SBA-C]. Radiation therapy is not generally indicated for jejunal lesions [SBA-E].
Ileal Adenocarcinoma
Adenocarcinoma arising in the ileum, the least common subsite. Distal ileal tumors are managed with segmentectomy plus right hemicolectomy [SBA-C]. Peritoneal carcinomatosis is more frequent from jejunal/ileal primaries than from duodenal primaries [108]. Surveillance screening is especially important in patients with Crohn's disease due to elevated risk [SBA-F].
dMMR/MSI-H or POLE/POLD1 Ultra-Hypermutated Phenotype
A molecular subtype defined by deficient mismatch repair (dMMR) resulting in microsatellite instability-high (MSI-H) or by polymerase epsilon/delta 1 (POLE/POLD1) mutations conferring an ultra-hypermutated phenotype (e.g., tumor mutational burden >50 mutations/Mb). This subtype is enriched in SBA compared to colorectal cancer, with dMMR occurring in a higher percentage of SBA [34,35]. It has distinct prognostic and therapeutic implications: patients may have improved survival in stage II (extrapolated from CRC data) and are candidates for immune checkpoint inhibitor therapy across all lines of treatment [SBA-D 2; SBA-D 3].
pMMR/MSS (Proficient MMR / Microsatellite Stable)
The majority of SBA cases, characterized by intact mismatch repair function and microsatellite stability. This subtype does not derive the same degree of benefit from immune checkpoint inhibitors as dMMR/MSI-H tumors, although pembrolizumab is a category 2A option for TMB-high (>10 mut/Mb) pMMR/MSS tumors [SBA-D 1]. Management follows standard chemotherapy-based approaches.
Molecular PathogenesisClick to collapse
Small bowel adenocarcinoma (SBA) has a distinct genomic landscape that sets it apart from colorectal cancer (CRC) and gastroesophageal cancers. Comprehensive genomic profiling studies have identified key driver mutations and pathways. KRAS and TP53 alterations are frequently identified in both SBA and CRC, but APC mutations are significantly less common in SBA (27%) compared to CRC (76%, P<.001), suggesting a unique mechanism of neoplastic transformation [35]. SMAD4 and CDKN2A mutations are more commonly observed in SBA than in CRC or gastroesophageal cancers [35]. BRAF mutations occur at a similar rate (~9.1% of SBA), but only about 10% of BRAF-mutant SBA harbor the V600E alteration, compared with >70% in BRAF-mutant CRC [35]. Human epidermal growth factor receptor 2 (HER2/ERBB2) alterations are enriched in SBA, with overexpression/amplification providing a therapeutic target [35,122]. Microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) is more prevalent in SBA than in CRC, with rates of TMB-high (>10 mutations/Mb) in approximately 9% to 11% of SBA versus 4.3% in CRC (P=.001) [35,155]. Programmed death-ligand 1 (PD-L1) expression is also enhanced in SBA, particularly in those associated with Crohn's disease or celiac disease [120,123]. POLE and POLD1 exonuclease domain mutations, though rare (incidence ~0.3% in both SBA and CRC), confer an ultra-hypermutated phenotype (often TMB>50 mut/Mb) and predict response to immune checkpoint inhibitors [35,152-154]. The frequency of RET and NTRK1/2/3 gene fusions is low but actionable, and testing via multigene panel testing (MGPT) is recommended [SBA-8]. WNT pathway alterations (CTNNB1, RNF43) and cell cycle regulators (CDKN2A, CCND1) are also implicated. The CpG island methylator phenotype (CIMP) may be present in a subset. The genomic profile underscores that SBA is a molecularly distinct entity from CRC, with implications for targeted therapy and immunotherapy selection [35].
Risk FactorsClick to collapse
Lynch syndrome (hereditary nonpolyposis colorectal cancer)
Germline mutations in MMR genes (MLH1, MSH2, MSH6, PMS2). Lifetime risk of SBA is 4%, representing a relative risk >100 compared to the general population [27,28]. Universal MMR/MSI testing is recommended for all SBA patients to identify Lynch syndrome [SBA-B].
Familial adenomatous polyposis (FAP)
Autosomal dominant germline mutation in APC gene (or MUTYH in attenuated FAP). Lifetime risk of SBA is estimated at 3% to 5%, with duodenum and periampullary region being the most common locations [18-20].
Peutz-Jeghers syndrome (PJS)
Autosomal dominant condition, majority due to STK11 (LKB1) mutations. Relative risk of SBA is 520 compared to general population; lifetime risk estimated between 1.7% and 13% [20,25,26]. Hamartomatous polyps predominantly in jejunum and ileum [20,21].
Crohn's disease (IBD)
Chronic inflammation of the small bowel. A retrospective multicenter cohort study of 9100 IBD patients found relative risk of small bowel cancer 3.70 (95% CI, 1.23–11.13) [11]. Distal SBA is more common. Rate of death and cancer remission did not differ between patients who maintained IBD treatment versus those who stopped [11].
Celiac disease
In a cohort study of 48,119 individuals with celiac disease, 0.06% (n=29) were diagnosed with SBA within 1 year of celiac diagnosis, suggesting a possible link [17]. Association is poorly understood and distinct from CRC (celiac disease is not a risk factor for CRC) [MS-3].
Alcohol consumption (high levels)
A systematic review reported high alcohol consumption may increase SBA risk [9]. A pooled analysis of over 500,000 individuals in the Asia Cohort Consortium showed a non-significant trend toward increased risk with high alcohol intake [10].
Smoking
Systematic review reported smoking may increase SBA risk [9]. However, the pooled Asia Cohort Consortium analysis did not identify smoking as a risk factor [10].
Dietary factors (low fiber, high red/processed meat, high sugary drinks)
Systematic review reported that low intake of fiber and high intake of red/processed meat and sugary drinks may increase the risk of SBA [9].
Elevated body mass index (BMI)
Pooled analysis of Asia Cohort Consortium reported elevated BMI was associated with a non-significant trend towards increased SBA risk [10].
Clinical FeaturesClick to collapse
Typical Presentation
Small bowel adenocarcinoma (SBA) presents with nonspecific symptoms that often delay diagnosis. The most common presentations are gastric outlet obstruction (for duodenal tumors), cramping abdominal pain (for jejunal/ileal tumors), and occult gastrointestinal bleeding, which occurs in approximately one-quarter to one-third of cases [MS-5]. Duodenal tumors account for 52%–58% of cases, jejunal 15%–29%, and ileal 10%–13% [MS-5]. Patients tend to be younger at diagnosis and present at a higher stage and grade compared to colorectal cancer [MS-5]. Many patients present emergently with malignant small bowel obstruction, accounting for 22%–57.9% of cases [MS-9]. Other features include weight loss, nausea, vomiting, and anemia. Due to the rarity of SBA and overlapping symptoms with benign conditions, the diagnosis is often made at an advanced stage.
Symptoms
Gastric outlet obstruction
Most common in duodenal SBA, presenting with postprandial vomiting, early satiety, and epigastric fullness
Cramping abdominal pain
Most common in jejunal or ileal SBA, often colicky and intermittent due to partial obstruction
Occult gastrointestinal bleeding
Presents as iron-deficiency anemia, melena, or hematochezia
Weight loss
Unintentional weight loss due to obstruction and malignancy
Nausea and vomiting
Often related to obstruction
Signs
Abdominal distension
Due to obstruction or peritoneal metastases
Palpable abdominal mass
May be felt in advanced disease
Jaundice
With duodenal tumors causing biliary obstruction
Fecal occult blood
Positive on guaiac testing
Red FlagsClick to collapse
Gastric outlet obstruction or small bowel obstruction requiring urgent intervention [SBA-2, SBA-4]
Unexplained iron-deficiency anemia due to occult gastrointestinal bleeding [MS-5]
Palpable abdominal mass or signs of peritoneal carcinomatosis
Rapid weight loss and cachexia
Jaundice in the setting of duodenal tumor
Emergency presentation with perforation or severe hemorrhage
Worsening abdominal pain in a patient with Crohn's disease or celiac disease [SBA-F]
Positive fecal occult blood with negative upper and lower endoscopy (suggests small bowel source)
InvestigationsClick to collapse
Diagnostic
Esophagogastroduodenoscopy (EGD) with biopsy
Primary method for detection and pathologic sampling of duodenal lesions; allows direct visualization and tissue acquisition [SBA-A 2 of 2]
Push- or device-assisted enteroscopy (double- or single-balloon enteroscopy)
May be used for diagnosis and biopsy of jejunal or ileal lesions, especially when other methods fail; also used for stricture evaluation [SBA-A 2 of 2]
Capsule endoscopy
Consider when radiographic and other endoscopic methods fail to identify a suspected primary lesion; not preferred for initial workup due to inability to obtain tissue [SBA-A 2 of 2]
CT enterography or MR enterography
May improve visualization of small bowel tumors when conventional CT or MR with contrast is insufficient [SBA-A 1 of 2]
Complete blood count (CBC), chemistry profile, CA 19-9, CEA
Baseline assessment of anemia, liver and renal function, and tumor markers for monitoring [SBA-1]
Staging
Chest/abdomen/pelvis CT with intravenous and oral contrast
Primary imaging for staging; evaluates local tumor extent and distant metastases to lung, liver, peritoneum, and nodes [SBA-A 1 of 2]
Chest CT (without contrast)
May be done without contrast unless combined with abdominal CT [SBA-A 1 of 2]
MRI of abdomen/pelvis with IV gadolinium
Alternative when IV iodinated contrast is contraindicated; useful for characterization of indeterminate liver lesions [SBA-A 1 of 2]
Magnetic resonance cholangiopancreatography (MRCP)
Used in initial workup of suspected duodenal malignancies, particularly with biliary obstruction, to distinguish primary site [SBA-A 1 of 2]
Endoscopic ultrasound (EUS)
Enhanced pre-therapeutic staging of proximal small bowel malignancies; discerns duodenal from ampullary, biliary, or pancreatic primaries [SBA-1, SBA-A 2 of 2]
FDG-PET/CT
Not indicated for routine staging; may be considered when CT or MR results are equivocal, including evaluation of potential peritoneal disease [SBA-A 1 of 2]
Diagnostic laparoscopy
Not routinely indicated for clearly resectable early-stage disease; may be considered when occult peritoneal or metastatic disease is suspected (locally advanced tumors, high-risk histology, elevated tumor markers, discordant findings) and when results would alter management [SBA-C]
Biomarkers
Mismatch repair (MMR) / microsatellite instability (MSI) testing
Universal testing recommended for all newly diagnosed SBA; important for prognosis, identification of Lynch syndrome, and treatment selection (especially checkpoint inhibitor therapy) [SBA-B]
KRAS and BRAF V600E mutations
Required for metastatic disease to guide targeted therapy; RAS status predicts lack of benefit from EGFR inhibitors [SBA-8, SBA-D 1 of 12]
HER2 (ERBB2) overexpression/amplification
Identifies patients who may benefit from HER2-directed therapies (e.g., trastuzumab, fam-trastuzumab deruxtecan) [SBA-D 1 of 12]
Tumor mutational burden (TMB)
TMB-high (>10 mut/Mb) identifies patients who may respond to pembrolizumab (category 2B) [SBA-D 1 of 12, SBA-D 3 of 12]
POLE/POLD1 mutation
Associated with ultra-hypermutated phenotype (TMB>50 mut/Mb) and potential benefit from checkpoint inhibitors [SBA-3, SBA-5, SBA-D 2 of 12]
NTRK 1/2/3 gene fusions
Identify patients who may benefit from tropomyosin receptor kinase (TRK) inhibitors (larotrectinib, entrectinib, repotrectinib) [SBA-D 1 of 12]
RET gene fusions
Identify patients who may benefit from selpercatinib [SBA-D 1 of 12]
StagingClick to collapse
AJCC 8th edition (2017) TNM staging for small intestine adenocarcinoma [ST-1]
T Categories
| Stage | Description |
|---|---|
| TX | Primary tumor cannot be assessed |
| T0 | No evidence of primary tumor |
| Tis | High-grade dysplasia / carcinoma in situ |
| T1 | Tumor invades the lamina propria or submucosa |
| T1a | Tumor invades the lamina propria |
| T1b | Tumor invades the submucosa |
| T2 | Tumor invades the muscularis propria |
| T3 | Tumor invades through the muscularis propria into the subserosa, or extends into nonperitonealized perimuscular tissue (mesentery or retroperitoneum) without serosal penetration |
| T4 | Tumor perforates the visceral peritoneum or directly invades other organs or structures (e.g., other loops of small intestine, mesentery of adjacent loops of bowel, abdominal wall by way of serosa; for duodenum only, invasion of pancreas or bile duct) |
N Categories
| Stage | Description |
|---|---|
| NX | Regional lymph nodes cannot be assessed |
| N0 | No regional lymph node metastasis |
| N1 | Metastasis in one or two regional lymph nodes |
| N2 | Metastasis in three or more regional lymph nodes |
M Categories
| Stage | Description |
|---|---|
| M0 | No distant metastasis |
| M1 | Distant metastasis present |
Stage Groupings
| Group | Criteria | Clinical Meaning | Five Yr Survival | Treatment Intent |
|---|---|---|---|---|
| Stage 0 | Tis, N0, M0 | High-grade dysplasia/carcinoma in situ; premalignant | Data not specifically reported for stage 0 | Curative (endoscopic or surgical resection) |
| Stage I | T1-2, N0, M0 | Tumor confined to lamina propria/submucosa (T1) or muscularis propria (T2), node-negative | Localized disease (stage I–III combined) 5-year relative survival ≈ 85% [MS-10] | Curative (resection alone; observation after surgery) |
| Stage IIA | T3, N0, M0 | Tumor extends through muscularis propria into subserosa or nonperitonealized perimuscular tissue, node-negative | See stage I (localized) | Curative (resection; adjuvant therapy considered for high-risk features) |
| Stage IIB | T4, N0, M0 | Tumor perforates visceral peritoneum or directly invades other organs/structures, node-negative; high-risk stage II | See stage I (localized) | Curative (resection; recommended adjuvant therapy for T4N0) |
| Stage IIIA | Any T, N1, M0 | Tumor with 1–2 positive regional lymph nodes | Localized disease (stage I–III combined) 5-year relative survival ≈ 85% [MS-10] | Curative (resection and adjuvant chemotherapy; consider chemoradiation for margin-positive duodenal cancer) |
| Stage IIIB | Any T, N2, M0 | Tumor with ≥3 positive regional lymph nodes; higher nodal burden | Localized disease (stage I–III combined) 5-year relative survival ≈ 85% [MS-10] | Curative (resection and adjuvant chemotherapy; consider chemoradiation for margin-positive duodenal cancer) |
| Stage IV | Any T, Any N, M1 | Distant metastatic disease (peritoneal cavity, liver, and other sites) | 5-year relative survival ≈ 42% [MS-10] | Palliative (systemic therapy, palliative diversion/stenting; rare metastasectomy in select patients) |
Staging Pearls
- T4 for duodenum includes invasion of pancreas or bile duct, which is not specified for other small bowel sites [ST-1]
- Regional lymph node groups differ by primary site: duodenum – retropancreatic, hepatic artery, inferior pancreaticoduodenal, superior mesenteric; jejunum/ileum – cecal/ileocolic (terminal ileum), superior mesenteric, mesenteric NOS [SBA-B]
- AJCC recommends minimum evaluation of 8 lymph nodes; NCCN recommends goal of at least 8 lymph nodes for adequate staging, but the College of American Pathologists notes no clear minimum has been established [SBA-B, SBA-C]
- For stage II disease, high-risk features include T4, close/positive margins, <5 lymph nodes (duodenal) or <8 (jejunal/ileal), tumor perforation, lymphovascular invasion, perineural invasion, poor differentiation [SBA-6]
- Stage III and IV SBA have significantly worse outcomes compared to earlier stages [MS-6]
- MSI-H/dMMR status may confer better prognosis in stage II, but this is extrapolated from colorectal cancer data [SBA-B]
Management PrinciplesClick to collapse
Small bowel adenocarcinoma (SBA) is a rare malignancy with rising incidence, accounting for approximately 3% of gastrointestinal cancers. Treatment philosophy emphasizes a multimodal approach tailored to anatomic subsite (duodenum vs. jejunum/ileum) and molecular profile (pMMR/MSS vs. dMMR/MSI-H or POLE/POLD1 ultra-hypermutated phenotype). Due to the scarcity of prospective data, many recommendations are extrapolated from colorectal cancer (CRC) studies, and enrollment in clinical trials is strongly encouraged for all stages[MS-1], [MS-2]. The NCCN Panel classifies all recommendations as category 2A unless otherwise noted. Management decisions are guided by resectability, performance status, and biomarker status, with curative-intent surgery for localized disease, neoadjuvant or induction therapy for borderline/unresectable presentations, and palliative systemic therapy for metastatic disease. A multidisciplinary team (MDT) evaluation at a high-volume center is essential, particularly when considering radiation therapy or complex surgical resections like pancreaticoduodenectomy.
Curative
Resectable localized SBA (stage I–III), including T1–2N0, T3N0 (with or without high-risk features), T4N0, and T Any N1–2
Surgical resection with en bloc removal of regional lymph nodes (goal ≥8 nodes)[SBA-C]. For duodenal pMMR/MSS tumors, resection alone; for dMMR/MSI-H tumors, neoadjuvant checkpoint inhibitor immunotherapy may be considered for T4 or bulky primaries[SBA-3], [SBA-5]. Adjuvant therapy is offered based on stage and molecular status: observation for stage I; for stage II pMMR/MSS, observation or chemotherapy (FOLFOX or CAPEOX for high-risk features); for stage III pMMR/MSS, FOLFOX or CAPEOX (3–6 months)[SBA-6]. For dMMR/MSI-H stage II or III, options include FOLFOX + atezolizumab or CAPEOX + atezolizumab or chemotherapy alone[SBA-7].
Neoadjuvant/Induction (to achieve resectability)
Locally unresectable or medically inoperable SBA
For pMMR/MSS: induction chemotherapy with FOLFOX, CAPEOX, FOLFIRINOX, or chemo/RT (duodenal only); for dMMR/MSI-H: checkpoint inhibitor immunotherapy as preferred option[SBA-2], [SBA-3], [SBA-4], [SBA-5]. Patients are reevaluated for conversion to resectable disease; if converted, proceed to surgery. For duodenal cancers that remain unresectable after induction chemotherapy, preoperative chemo/RT may be considered[SBA-E].
Palliative
Distant metastatic SBA (stage IV) or unresectable recurrence
Palliative diversion or stenting for obstruction; systemic therapy based on MMR/MSI status and biomarkers. For pMMR/MSS: FOLFOX, CAPEOX, FOLFIRI, or FOLFIRINOX ± bevacizumab (intensive therapy), or fluoropyrimidine monotherapy ± bevacizumab (non-intensive). For dMMR/MSI-H or POLE/POLD1: checkpoint inhibitor immunotherapy (PD-1, PD-L1, or CTLA-4 inhibitors) as any-line therapy[SBA-D 1-2]. Second-line and subsequent therapy includes taxane-based chemotherapy and biomarker-directed agents (e.g., for BRAF V600E, HER2, NTRK, RET, KRAS G12C)[SBA-D 1].
Surveillance
All patients after curative-intent treatment
History and physical examination every 3–6 months for 2 years, then every 6 months for 5 years; CEA and CA 19-9 every 3–6 months for 2 years, then every 6 months for 5 years; chest/abdomen/pelvis CT every 6–12 months for 2 years, then every 12 months for years 3–5. FDG-PET/CT and routine capsule endoscopy are not indicated[SBA-6], [SBA-7]. Surveillance intervals are extrapolated from CRC data[SBA-6 footnote p].
A multidisciplinary team including surgical oncology, medical oncology, radiation oncology, pathology, radiology, gastroenterology, and genetic counseling is essential for treatment planning. For duodenal primaries, high-volume centers are recommended when RT or complex surgery is considered[SBA-E]. Participation in clinical trials is particularly important given the rarity of SBA and limited data[MS-1].
Performance status (PS) guides intensity of therapy. For advanced/metastatic disease, patients with good PS (ECOG 0–2) are candidates for intensive combination regimens (FOLFOX, CAPEOX, FOLFIRINOX ± bevacizumab). For older adults or those with poor PS, geriatric assessment is recommended to predict treatment risks[SBA-D 3 footnote h]. Non-intensive options (fluorouracil/leucovorin or capecitabine ± bevacizumab) are appropriate for patients who are not candidates for intensive therapy. Checkpoint inhibitor immunotherapy is suitable for dMMR/MSI-H patients regardless of PS, provided no contraindications.
Management PathwaysClick to collapse
Branching: Anatomic site: duodenum, MMR/MSI status: pMMR/MSS, Resectability: resectable
Branching: Anatomic site: duodenum, MMR/MSI status: pMMR/MSS, Resectability: locally unresectable or inoperable
Branching: Anatomic site: duodenum, MMR/MSI status: pMMR/MSS, Distant metastases present
Branching: Anatomic site: duodenum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1 ultra-hypermutated (e.g., TMB>50 mut/Mb), Resectability: resectable
Branching: Anatomic site: duodenum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1, Resectability: locally unresectable or inoperable
Branching: Anatomic site: duodenum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1, Distant metastases present
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: pMMR/MSS, Resectability: resectable
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: pMMR/MSS, Resectability: locally unresectable or inoperable
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: pMMR/MSS, Distant metastases present
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1, Resectability: resectable
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1, Resectability: locally unresectable or inoperable
Branching: Anatomic site: jejunum/ileum, MMR/MSI status: dMMR/MSI-H or POLE/POLD1, Distant metastases present
Branching: MMR/MSI status: pMMR/MSS, Pathologic stage
Branching: MMR/MSI status: dMMR/MSI-H or POLE/POLD1 ultra-hypermutated (TMB>50 mut/Mb), Pathologic stage
Branching: Distant metastatic or recurrent disease, Biomarker profile (RAS, BRAF, HER2, MMR, TMB, NTRK, RET, KRAS G12C)
Pretreatment EvaluationClick to collapse
Imaging
Endoscopy
Laboratory and Biomarker Testing
Pathologic Review
Genetic/Familial Risk Assessment
Other Evaluations
SurgeryClick to collapse
Surgery is the only curative treatment for localized SBA. The primary goal is complete (R0) resection of the primary tumor with adequate lymphadenectomy (≥8 lymph nodes). Surgical approach is determined by anatomic subsite, tumor extent, and patient factors. Diagnostic laparoscopy is not routinely indicated for clearly resectable early-stage disease but may be considered when occult peritoneal or metastatic disease is suspected (locally advanced tumors, high-risk histology, elevated tumor markers, or discordant findings) and when results would alter management[SBA-C].
Intraoperative staging of the abdomen (mesentery, omentum, peritoneum) should be completed in all cases[SBA-C].
Adequate lymph node dissection with retrieval and evaluation of at least 8 lymph nodes (AJCC recommendation) is a goal for all resections. The number of nodes examined is a strong prognostic factor[SBA-C], [SBA-B].
Diagnostic laparoscopy not routine for early-stage resectable disease; consider for specific scenarios where occult metastases suspected and management would be altered[SBA-C].
Margins: for duodenal resections, consider frozen section if concerns; if margins <5 mm, consider re-excision of involved margin[SBA-C].
Specimen orientation and inking involve both surgeon and pathologist to ensure accurate assessment of size, extent, and margin status[SBA-B].
Procedures
Pancreaticoduodenectomy (Whipple procedure)
All duodenal malignancies, particularly those arising in second portion of duodenum or invading any portion of ampulla or pancreas[SBA-C].
Limited segmentectomy (duodenum)
Select cases for lesions on anti-mesenteric side involving third and fourth segments of duodenum, or for lesions in first portion of duodenum <2 cm on mesenteric side. Controversial; lower lymph node yield reported[SBA-C], [SBA-2].
Segmentectomy (jejunum/ileum)
Standard for jejunal and ileal adenocarcinomas. Margins of at least 5–10 cm on either side of tumor[SBA-C].
Terminal ileal resection with right hemicolectomy
Distal ileal tumors (terminal ileum). Includes resection of cecum and ascending colon to ensure adequate lymphadenectomy[SBA-C].
Radiation TherapyClick to collapse
Radiation therapy (RT) is used primarily for duodenal adenocarcinoma. It is not generally indicated for jejunum/ileum primaries; any consideration for these sites must be made on a highly selected basis by a multidisciplinary team[SBA-E]. For duodenal cancer, RT is considered in the following settings: (1) adjuvant sequential chemoradiation after systemic therapy for margin-positive resections; (2) preoperative chemoradiation for patients who remain unresectable after a course of induction chemotherapy; (3) primary chemoradiation for locally unresectable disease as part of management. Database analysis suggests no survival benefit from adjuvant chemo/RT versus chemotherapy alone in patients with surgically resected duodenal adenocarcinoma[SBA-E].
Principles
- Fluoropyrimidine-based chemotherapy should be delivered concurrently with RT (capecitabine 825 mg/m² PO BID on radiation days, or infusional fluorouracil 225 mg/m²/day continuous infusion during RT)[SBA-D 4], [SBA-D 6].
- Treatment can be delivered using 3D-CRT. When appropriate, advanced treatment planning such as IMRT should be considered to limit toxicity to adjacent normal organs[SBA-E].
- Image-guided RT (IGRT) with kV imaging, MR-guided imaging, or cone beam CT should be routinely used during IMRT[SBA-E].
- Target volumes should include the primary site and regional lymph node basins (e.g., retropancreatic, hepatic artery, inferior pancreaticoduodenal, superior mesenteric for duodenum)[SBA-E].
- Patients should be evaluated by multidisciplinary teams at high-volume centers when RT is considered[SBA-E].
Dose Frameworks
| Name | Total Dose | Dose Per Fraction | Fractions | Schedule | Indication |
|---|---|---|---|---|---|
| Standard fractionation for duodenal RT | 45–54 Gy | 1.8–2 Gy | 25–30 fractions | Daily, Monday–Friday | Adjuvant (margin-positive), preoperative (unresectable after induction), or definitive for duodenal primary. Dose determined by tolerance of adjacent normal tissues[SBA-E]. |
Approaches
| Name | Dose Fractionation | Concurrent Chemotherapy | Indication | Key Trial | Toxicities |
|---|---|---|---|---|---|
| Adjuvant sequential chemoradiation for duodenal cancer | 45–54 Gy in 1.8–2 Gy daily fractions | Capecitabine 825 mg/m² PO BID on radiation days or infusional fluorouracil 225 mg/m²/day continuous infusion during RT[SBA-D 4] | Stage II–III duodenal pMMR/MSS or dMMR/MSI-H with positive margins after resection, following systemic therapy[SBA-6 footnotes n and o], [SBA-7 footnote o] | No SBA-specific phase III data; extrapolation from rectal cancer studies (Allegra et al., JNCI 2015)[SBA-D 4 reference 4] | Acute: nausea, vomiting, diarrhea, dermatitis, fatigue, myelosuppression. Late: small bowel stricture, enteritis, fistula (dose constraints: adjacent small bowel Dmax 55 Gy, V45Gy ≤150 cc, V50 ≤30 cc for individual loops if possible)[SBA-E]. |
| Preoperative chemoradiation for initially unresectable duodenal cancer | 45–54 Gy in 1.8–2 Gy daily fractions | Capecitabine or infusional fluorouracil as above | Locally unresectable duodenal adenocarcinoma after induction chemotherapy, to achieve conversion to resectable disease[SBA-2 footnote i], [SBA-3 footnote i], [SBA-E] | Small retrospective series (Onkendi et al., J Gastrointest Surg 2012)[SBA-E reference 2]; prospective phase II (Yeung et al., Cancer 1993)[MS-9] | Similar to above; includes radiation-induced edema, pancreatitis if pancreas included in field. |
| Definitive chemoradiation for medically inoperable duodenal cancer | 50.4–54 Gy in 1.8–2 Gy fractions | Capecitabine or infusional fluorouracil | Medically inoperable or unresectable duodenal cancer without metastases | Limited data; considered when systemic therapy alone insufficient | Acute and late as above; may require dose reduction if adjacent small bowel dose constraints cannot be met. |
Systemic TherapyClick to collapse
Many systemic therapy regimens for SBA are extrapolated from data for colorectal cancer (CRC) due to the rarity of SBA and lack of dedicated trials. The NCCN Panel strongly encourages enrollment in clinical trials for all SBA patients[MS-1]. Systemic therapy is used in the adjuvant setting (after resection of localized disease) and in advanced/metastatic disease. The choice of regimen depends on MMR/MSI status, biomarker profile (RAS, BRAF V600E, HER2, NTRK, RET, KRAS G12C, TMB), prior therapy, performance status, and treatment goals (adjuvant vs. palliative). For advanced disease, initial intensive therapy is recommended for patients with good PS (ECOG 0–2) and includes oxaliplatin- or irinotecan-based doublets/triplets ± bevacizumab. Non-intensive therapy (fluoropyrimidine alone ± bevacizumab) is for patients who are not candidates for intensive therapy. For dMMR/MSI-H or POLE/POLD1 ultra-hypermutated tumors, checkpoint inhibitor immunotherapy is preferred at any line[SBA-D 1-2]. Bevacizumab has been shown to be safe in advanced SBA, although efficacy has not been proven; an FDA-approved biosimilar may be substituted[SBA-D 3 footnote f,c]. Oxaliplatin discontinuation after 3–4 months (or sooner for neurotoxicity) is recommended, while maintaining other agents[SBA-D 3 footnote e].
Key Regimens
Treatment Response AssessmentClick to collapse
Title
Treatment Response Assessment for Small Bowel Adenocarcinoma
Timing
Response assessment is performed at multiple time points: after completion of neoadjuvant therapy (to evaluate conversion to resectability), after surgery (baseline for adjuvant decision), during adjuvant therapy (not routinely; mainly to monitor toxicity), during palliative systemic therapy for advanced/metastatic disease (typically every 2–3 months or after 2–4 cycles), after completion of adjuvant therapy (to establish new baseline for surveillance), and when clinical suspicion of recurrence arises. For patients undergoing systemic therapy for advanced disease, imaging (chest/abdomen/pelvis CT with contrast) is recommended every 8–12 weeks or per clinical need[SBA-A 2]. Biomarker levels (CEA and CA 19-9) may be checked at the time of imaging, though no prospective data support tight interval substitution for imaging.
Response Logic
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For neoadjuvant therapy (induction chemo or chemo/RT): After 2–4 months, repeat CT chest/abdomen/pelvis to assess response. If conversion to resectable occurs, proceed to surgery. If stable disease or progression, consider alternative systemic therapy or RT (especially for duodenal primaries with positive margins). Preoperative chemo/RT should be considered in patients who remain unresectable after induction chemotherapy[SBA-2 footnote i], [SBA-E].
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For first-line palliative therapy: Imaging after 2–3 months (e.g., after 4 cycles of FOLFOX). If response or stable disease, continue therapy (with consideration of oxaliplatin break after 3–4 months). If progression, switch to second-line therapy. If mixed response, consider local ablative options for limited progression. FDG-PET/CT is not routinely indicated but may be considered when CT/MR results are equivocal[SBA-A 1].
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For immunotherapy: Response may be delayed or pseudoprogression; confirm progression on subsequent imaging if clinical stability. Continue immunotherapy until confirmed progression, unacceptable toxicity, or up to 2 years (for pembrolizumab, per FDA label).
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For biomarker-directed therapy: Assess target lesions with CT/MR every 2–3 cycles. For targeted agents with known high response rates (e.g., dabrafenib/trametinib, selpercatinib), early response is common. Confirm response at first assessment.
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After curative-intent surgery and adjuvant therapy: No response assessment beyond baseline staging is required; routine surveillance for recurrence per schedule (H&P, CEA/CA19-9, CT every 6–12 months for 2 years, then annually)[SBA-6], [SBA-7].
Imaging Recommendations
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Use same modality (CT vs. MR) for consistent comparison. CT chest/abdomen/pelvis with IV contrast (oral contrast as needed) is standard[SBA-A 1].
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If CT contraindicated, MR abdomen/pelvis with IV gadolinium-based contrast is acceptable[SBA-A 1].
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CT enterography not routinely indicated for monitoring; reserved for clinical necessity[SBA-A 2].
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FDG-PET/CT is not indicated for routine surveillance or response assessment; may be considered for equivocal findings on CT/MR and when detection of peritoneal disease is important (lesions > lower limits of FDG detection)[SBA-A 1].
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In patients with serial biomarker elevation (CEA, CA 19-9) but no evidence of disease on CT, consider FDG-PET/CT and endoscopic evaluation. If still negative, repeat CT and biomarkers in 3 months[SBA-8].
Biopsy Or Salvage Logic
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If recurrence is suspected based on imaging or biomarker elevation, tissue biopsy (endoscopic or CT-guided) is recommended to confirm recurrence and to reassess biomarker status (MMR/MSI, RAS, BRAF, HER2, etc.) as molecular profile may change. For oligometastatic recurrence (e.g., solitary liver or lung metastasis), consider metastasectomy after multidisciplinary evaluation[SBA-8 footnote r].
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Potentially resectable visceral or peritoneal metastases are extremely rare for SBA. If considered, evaluation by a surgeon experienced in metastasectomy and/or cytoreductive surgery (CRS) is required. HIPEC is not recommended due to lack of evidence and significant morbidity[SBA-8 footnote r], [MS-10]. Proceed to systemic therapy per metastatic guidelines if unresectable.
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If a patient with localized disease had R1 resection (microscopic positive margin) and received adjuvant chemo/RT, and then develops local recurrence, consider re-resection if feasible, otherwise systemic therapy.
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For patients who progress on first-line immunotherapy, consider switching to chemotherapy (FOLFOX/CAPEOX/FOLFIRINOX) if not previously given, or enrollment in clinical trial. For progression on chemotherapy, explore second-line options including clinical trials and biomarker-directed therapy.
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Best supportive care is an option at any point when disease is refractory and no further active therapy is appropriate.
SurveillanceClick to collapse
Clinical Follow Up Schedule
| Interval | Frequency | Components |
|---|---|---|
| Years 1-2 | Every 3-6 months | History and physical examination, CEA, CA 19-9, chest/abdomen/pelvis CT every 6-12 months |
| Years 3-5 | Every 6 months for H&P and tumor markers; annually for CT | History and physical examination every 6 months, CEA and CA 19-9 every 6 months, chest/abdomen/pelvis CT every 12 months |
| Beyond 5 years | Annually or as clinically indicated | Continue surveillance based on risk factors (e.g., Lynch syndrome, Crohn's disease). Consider small bowel endoscopy for high-risk patients. |
Imaging Strategy
- Chest/abdomen/pelvis CT with IV iodinated contrast and oral contrast is the standard for surveillance. If IV contrast is contraindicated, MR abdomen/pelvis with gadolinium-based contrast may be used (specific agents: gadobutrol, gadopentetate dimeglumine, gadobenate dimeglumine, gadoteridol in chronic kidney disease) [SBA-A 1 of 2 reference 1]
- CT enterography is not routinely indicated for surveillance but may be reserved for instances of clinical necessity when primary tumor is poorly visualized by standard methods [SBA-A 2 of 2]
- FDG-PET/CT is not indicated for routine surveillance. It may be considered if CT or MR results are equivocal, including evaluation of potential peritoneal disease where lesions are larger than the lower limits of FDG-PET detection [SBA-A 1 of 2]
- Capsule endoscopy is not indicated for routine surveillance and is contraindicated if small bowel obstruction or strictures exist [SBA-A 2 of 2]
Laboratory Monitoring
- CEA and CA 19-9 every 3-6 months for 2 years, then every 6 months for a total of 5 years [SBA-6, SBA-7]
- CBC and chemistry profile may be monitored to assess for therapy-related toxicities and overall health status
- For patients on immunotherapy, monitor thyroid function, liver function, and other irAE labs per NCCN guidelines for immune-related toxicity management
- For patients on targeted therapies (e.g., dabrafenib/trametinib, selpercatinib), follow prescribing information for required monitoring (e.g., LFTs, creatinine, cardiac function)
Supportive Follow Up
- Survivorship care planning: provide patient with a treatment summary including dates of surgery, chemotherapy (drugs, cycles), and radiation (dose, fields) [SBA-F]
- Manage late/long-term sequelae: peripheral neuropathy, fatigue, pain, sexual dysfunction, distress. Refer to NCCN Guidelines for Survivorship [SBA-F]
- Lifestyle modifications: encourage plant-based diet, healthy body weight, regular physical activity, avoidance of alcohol and tobacco. See NCCN Guidelines for Smoking Cessation [SBA-F]
- Patients with confirmed celiac disease: avoid gluten [SBA-F]
- Patients with Crohn's disease: remain at elevated risk for further SBAs; consider surveillance screening [SBA-F references 1,2]
- Fertility counseling: discussed at end of treatment [SBA-F]
- All age- and gender-appropriate preventive health and cancer screenings should be maintained with primary care provider [SBA-F]
ComplicationsClick to collapse
Disease-Related
| Complication | Management |
|---|---|
| Small bowel obstruction | Palliative diversion, stenting (endoscopic or surgical bypass). Obstruction is common, accounting for 22-57.9% of presentations [41,98-100]. Stent placement may be considered for duodenal obstruction; surgical bypass for jejunal/ileal obstruction [SBA-2, SBA-4]. |
| Gastric outlet obstruction (duodenal tumors) | Palliative diversion or stent [SBA-2]. Endoscopic duodenal stenting may provide relief; however, survival after stenting is limited [101]. |
| Occult gastrointestinal bleeding | Occurs in approximately 25-33% of cases [36,41]. Endoscopic evaluation, transfusion support, and definitive treatment of primary tumor. |
| Peritoneal carcinomatosis | Affects 25-50% of stage IV patients [108]. Surgical cytoreduction may be considered for resectable disease; systemic therapy for unresectable. HIPEC is not recommended due to lack of evidence [109-115]. Median OS 5.9 months [109]. |
| Biliary obstruction (duodenal tumors) | MRCP may be needed to distinguish duodenal from ampullary/pancreatic primaries [SBA-A]. Endoscopic drainage or stenting may be required. |
| Malnutrition and weight loss | Nutritional support, dietary modification. Consider celiac disease evaluation in appropriate patients. |
Supportive CareClick to collapse
Supportive care for SBA patients largely follows principles established for colorectal cancer, given the rarity of SBA-specific data. Key elements include nutritional support, antiemetic management, growth factor support, VTE prophylaxis, pain management, psychosocial support, and dental care. All patients should be screened for distress using the NCCN Distress Thermometer and Problem List, which includes social determinants of health [SBA-1 footnote c]. DPYD testing should be considered before starting fluoropyrimidine therapy [SBA-1 footnote b, SBA-D 3 footnote d].
Patients with SBA are at high risk for malnutrition due to bowel obstruction, malabsorption (especially in duodenal primaries and after Whipple surgery), and treatment side effects. Nutritional assessment and intervention (dietary counseling, oral supplements, or enteral/parenteral nutrition) should be provided. For patients with celiac disease, strict gluten avoidance is critical [SBA-F]. After pancreaticoduodenectomy, pancreatic enzyme replacement may be needed. Cachexia should be managed with a multidisciplinary approach including dietitian, physical therapy, and psychological support.
Standard prophylaxis for moderate-to-high emetic risk chemotherapy (carboplatin, oxaliplatin, irinotecan) includes a neurokinin-1 (NK1) receptor antagonist, a serotonin (5-HT3) receptor antagonist, and dexamethasone. For low emetic risk regimens (fluorouracil, capecitabine), a 5-HT3 antagonist or dexamethasone alone may be sufficient. The NCCN Guidelines for Antiemesis should be followed. Prophylaxis for delayed emesis is particularly important with oxaliplatin-based regimens.
Primary prophylaxis with granulocyte colony-stimulating factor (GCSF) is recommended for regimens with a high risk (>20%) of febrile neutropenia. For SBA, standard regimens (FOLFOX, FOLFOXIRI) have moderate risk of neutropenia. The NCCN Guidelines for Myeloid Growth Factors should be consulted for specific recommendations based on regimen and patient risk factors.
Cancer-associated thrombosis prevention should follow established guidelines. For ambulatory patients with metastatic SBA on active systemic therapy, consider prophylactic anticoagulation (low molecular weight heparin or direct oral anticoagulants) based on Khorana risk score or other validated tools. Patients undergoing major abdominal surgery (Whipple, segmentectomy) should receive perioperative VTE prophylaxis as per standard surgical protocols.
Pain in SBA may arise from tumor obstruction, peritoneal involvement, neuropathic pain (oxaliplatin), or postoperative causes. For neuropathic pain from oxaliplatin, duloxetine, pregabalin, or gabapentin may be used only if pain is present; they are ineffective for numbness or tingling [SBA-F]. Non-pharmacologic interventions such as acupuncture, heat/ice, and balanced physical activity should be considered [SBA-F]. See NCCN Guidelines for Adult Cancer Pain for comprehensive management.
All patients should undergo distress screening using the NCCN Distress Thermometer. Survivorship care planning includes addressing emotional distress, social concerns, financial toxicity, and sexual dysfunction. Referral to social work, psychology, or psychiatry as needed. Support groups for rare cancers may be beneficial. See NCCN Guidelines for Distress Management.
Dental evaluation before initiating chemotherapy is recommended to reduce the risk of oral mucositis and infection. Good oral hygiene, fluoride treatments, and management of xerostomia may help during treatment with 5-FU or capecitabine. For patients receiving bisphosphonates or denosumab (not typically used in SBA), dental assessment is essential to prevent osteonecrosis of the jaw.
PrognosisClick to collapse
Small bowel adenocarcinoma (SBA) has a rising incidence, with an estimated 12,440 new cases and 2,090 deaths in the United States in 2024 [1]. The overall 5-year relative survival for all stages combined is approximately 65-70%, with localized disease (stage I-III) having a 5-year survival of 85% and distant metastatic (stage IV) disease a 5-year survival of only 42% [105]. SBA is often diagnosed at a higher stage than colorectal cancer, contributing to worse stage-for-stage survival. The median age at diagnosis is 66 years, with a slight male predominance (incidence 2.6 per 100,000 for males vs. 2.0 for females) [2,40].
By Stage
| Stage | Five Yr Survival | Context |
|---|---|---|
| Stage I (T1-2, N0, M0) | 85% (localized disease, includes stage I-III) | Based on SEER data for localized SBA (stage I-III) [105]. Specific stage I survival not explicitly separated but prognosis is excellent with complete resection. |
| Stage IIA (T3, N0, M0) and IIB (T4, N0, M0) | 85% (localized combined) | Stage IIA no high-risk features may have observation alone; stage IIB (T4) considered high-risk and often considered for adjuvant therapy [SBA-6]. dMMR/MSI-H stage II patients may have improved prognosis but this is extrapolated from colorectal cancer data [SBA-B]. |
| Stage IIIA (any T, N1, M0) and IIIB (any T, N2, M0) | 85% (localized combined) | Stage III disease with lymph node involvement has significantly worse outcomes compared to stage I-II. Adjuvant chemotherapy (FOLFOX or CAPEOX) is recommended for stage III pMMR/MSS tumors [SBA-6]. Five-year survival for stage III is not explicitly given but recurrence rates after surgery are high [36]. |
| Stage IV (any T, any N, M1) | 42% | Distant metastatic disease. Median OS in clinical trials: with FOLFOX, median OS 17.3 months [128]; with CAPEOX, median OS 17.3 months [126]; with pembrolizumab in MSI-H SBA, median OS not reached at time of publication (KEYNOTE-158) [142]. Peritoneal carcinomatosis carries particularly poor prognosis with median OS 5.9 months [109]. |
Prognostic Factors
- Lymph node status: number of positive nodes (N1 vs N2) and lymph node ratio [60-62]
- Lymph node harvest: <5 nodes for duodenal, <8 for jejunal/ileal tumors considered inadequate [40,60,61]
- Tumor grade: poorly differentiated histology [76]
- Margin status: positive margins (R1/R2) worsen prognosis [SBA-6]
- Tumor perforation [SBA-6]
- Lymphovascular invasion (LVI) and perineural invasion (PNI) [76,92-94]
- MSI/MMR status: dMMR/MSI-H may be associated with better prognosis in stage II (extrapolated from CRC) but also predicts response to immunotherapy [SBA-B]
- Primary tumor site: duodenal tumors may have different outcomes than jejunal/ileal [36]
- Genetic alterations: BRAF V600E, RAS mutations, HER2 amplification, POLE/POLD1 mutations [35]
- Tumor mutational burden (TMB): TMB-high (>10 mut/Mb) found in 9-11% of SBA, associated with immunotherapy response [35,155]
- Inflammatory conditions: Crohn's disease and celiac disease confer increased risk but impact on prognosis not fully defined [11,12,17]
Follow UpClick to collapse
Post Curative Treatment
After curative-intent surgery and adjuvant chemotherapy (if administered), follow-up surveillance is recommended to detect recurrence and manage treatment-related complications. The NCCN Panel recommends a similar approach to colorectal cancer surveillance due to the lack of SBA-specific data [SBA-6, SBA-7]. The schedule is as follows: history and physical examination every 3-6 months for the first 2 years, then every 6 months for a total of 5 years; CEA and CA 19-9 every 3-6 months for 2 years, then every 6 months for a total of 5 years; chest/abdomen/pelvis CT with contrast every 6-12 months for 2 years, then every 12 months for years 3-5. FDG-PET/CT is not indicated for routine surveillance. Routine capsule endoscopy is not indicated [SBA-6, SBA-7]. Patients with Lynch syndrome should have appropriate screenings commensurate with their genotype and family cancer history, which may include small intestinal screening [SBA-A 2 of 2 reference 13]. Patients with Crohn's disease and history of SBA remain at elevated risk for further SBAs and surveillance screening should be considered [SBA-F].
Surveillance Rationale
A retrospective study found that 39% of patients with SBA who underwent cancer-directed surgery developed recurrence, with median time to recurrence of 25 months [36]. Among recurrences, 57% were distant metastases, 19% carcinomatosis, 7% abdominal wall, and 17% local. Because of this high recurrence rate, routine surveillance is recommended. However, no prospective studies have validated surveillance intervals for SBA, so the Panel endorses the colorectal cancer surveillance paradigm [SBA-6 footnote p].
Late Effects Screening
- Oxaliplatin-induced peripheral neuropathy: screen for persistent numbness, tingling, or pain. Only treat pain component with duloxetine, gabapentin, or pregabalin [SBA-F]
- Chronic diarrhea or malabsorption: especially after Whipple surgery or extensive small bowel resection; manage with pancreatic enzymes, antidiarrheals, and dietary modifications
- Secondary primary malignancies: patients with Lynch syndrome, FAP, or PJS are at risk for other cancers (colorectal, endometrial, gastric, etc.) and should undergo appropriate screening [SBA-1]
- Crohn's disease patients: remain at risk for further SBAs; surveillance endoscopy may be considered [SBA-F]
- Celiac disease patients: continue gluten-free diet; association with SBA suggests possible increased risk of metachronous lesions [SBA-F]
- Psychosocial and functional status: screen for distress, fatigue, sexual dysfunction, and fertility concerns; refer to NCCN Guidelines for Survivorship
Recurrence Patterns
Recurrence after curative-intent treatment is common. Local recurrence is less frequent than distant metastases (17% local vs. 57% distant) [36]. Peritoneal carcinomatosis occurs in 25-50% of metastatic cases [108]. Distant metastases most commonly involve the liver and peritoneal cavity. Elevated CEA or CA 19-9 may precede radiographic recurrence. Workup for suspected recurrence includes chest/abdomen/pelvis CT with contrast, endoscopy if indicated, and biomarker testing (including RAS, BRAF V600E, HER2, MMR/MSI, TMB, NTRK, RET, POLE/POLD1). FDG-PET/CT may be considered if CT/MR results are equivocal [SBA-8].
Key TrialsClick to collapse
| Acronym | Full Name | Year | N | Intervention | Comparator | Population | Primary Endpoint | Key Result | Secondary Outcomes | Practice Change | Journal |
|---|---|---|---|---|---|---|---|---|---|---|---|
| BALLAD | GLOBAL BALLAD: An International Rare Cancers Initiative trial to evaluate the potential benefit of adjuvant chemotherapy for small bowel adenocarcinoma (IRCI 002) | Ongoing (initial report 2016) | Unknown (phase III, ongoing) | 5-FU/leucovorin or FOLFOX | Observation | Patients with resected stage I-III SBA | Overall survival | Trial not yet completed; currently enrolling. | Not yet reported | Pending results. Currently, adjuvant therapy for SBA is based on retrospective data and extrapolation from colon cancer. | Journal of Clinical Oncology (abstract) |
| ZEBRA | A Multicenter Phase II Study of Pembrolizumab in Patients with Advanced Small-Bowel Adenocarcinoma | 2021 | 40 | Pembrolizumab 200 mg every 3 weeks | Single-arm | Previously treated advanced SBA (any MMR/MSI status) | Overall response rate (ORR) | ORR did not meet prespecified endpoint; 50% of MSI-H patients (n=4) had partial response and remained alive without progression; one MSS patient had partial response (also TMB-H). Disease control rate 38%. | 63% grade ≥3 AEs, 28% grade 4-5 AEs. Median PFS 2.9 months overall. | Supports use of pembrolizumab in MSI-H advanced SBA; suggests TMB-H may also predict benefit. | Clinical Cancer Research |
| KEYNOTE-158 | Efficacy of Pembrolizumab in Patients With Noncolorectal High Microsatellite Instability/Mismatch Repair-Deficient Cancer | 2020 | 233 (19 with SBA)" | Pembrolizumab 200 mg every 3 weeks | Single-arm | dMMR/MSI-H advanced non-CRC solid tumors, including SBA | ORR | Whole population ORR 34.3%; SBA cohort ORR 42.1% (3 complete responses). Median PFS for SBA: 9.2 months. Median OS for SBA: not reached at publication. | Median duration of response not reached for SBA. | Major support for pembrolizumab in MSI-H advanced SBA. Led to FDA tissue-agnostic approval for dMMR/MSI-H tumors. | Journal of Clinical Oncology |
| CheckMate 142 | Nivolumab in patients with metastatic DNA mismatch repair-deficient or microsatellite instability-high colorectal cancer | 2017 (nivolumab monotherapy) and 2018 (nivolumab + ipilimumab) | 74 (nivolumab monotherapy), 119 (nivolumab + ipilimumab) | Nivolumab 3 mg/kg every 2 weeks OR nivolumab + ipilimumab (3 mg/kg + 1 mg/kg) every 3 weeks x4 then nivolumab maintenance | Single-arm cohorts | dMMR/MSI-H metastatic colorectal cancer (no SBA specifically, but extrapolated) | ORR by investigator | Nivolumab monotherapy: ORR 31.1% (95% CI 20.8-42.9), 1-year PFS 50%, 1-year OS 73%. Nivolumab + ipilimumab: ORR 55% (95% CI 45.2-63.8), 1-year PFS 71%, 1-year OS 85%. | Grade 3-4 AEs: 20% monotherapy, 32% combination. Significant improvements in patient-reported outcomes in combination arm. | Established nivolumab ± ipilimumab as standard in dMMR/MSI-H CRC; extended to SBA by class effect. | Lancet Oncology (2017), Journal of Clinical Oncology (2018) |
| DART SWOG S1609 | A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors: Small bowel cancer cohort | 2021 | 23 | Nivolumab + ipilimumab | Single-arm | Rare tumors including small bowel cancer | ORR | ORR 8% (1 complete response, 1 partial response). Median PFS 2 months, median OS 6 months. | Toxicity profile consistent with known irAEs. | Modest activity in unselected small bowel cancer; supports biomarker-directed use (MSI-H). | Cancer (from abstract) |
| ROAR | Phase 2 ROAR trial: Dabrafenib plus trametinib in BRAF V600E-mutated rare cancers | 2023 | 3 patients with adenocarcinoma of small intestine (in cohort, total n across cohorts 181) | Dabrafenib 150 mg BID + trametinib 2 mg daily | Single-arm | BRAF V600E-mutated advanced rare cancers, including SBA | ORR by investigator | ORR 67% (2 of 3) in small intestine cohort. For all cohorts: median DoR 7.7 months in small intestine, median PFS not evaluable, median OS 21.8 months. | Grade ≥3 AEs in 87.9% across all cohorts; pyrexia most common (40.8%). Fatal SAEs in 4.4%. | FDA approval of dabrafenib + trametinib for BRAF V600E-mutated solid tumors (tissue-agnostic) [161]. | Nature Medicine |
| DESTINY-PanTumor02 | Trastuzumab Deruxtecan in Patients With HER2-Expressing Solid Tumors | 2024 | 267 (1 patient with intestinal adenocarcinoma in rare tumor cohort)" | Fam-trastuzumab deruxtecan 5.4 mg/kg every 3 weeks | Single-arm | HER2-expressing (IHC 3+ or 2+) advanced solid tumors | ORR by independent review | Overall ORR 37.1% (95% CI 31.3-43.2). In IHC 3+ patients (n=75): ORR 61.3%, median DOR 22.1 mo, median PFS 11.9 mo, median OS 21.1 mo. ILD/pneumonitis in 20.5%. | Median DOR 11.3 months overall. | Supports use of fam-trastuzumab deruxtecan in HER2 IHC 3+ solid tumors. | Journal of Clinical Oncology |
| DESTINY-CRC02 | Trastuzumab Deruxtecan (T-DXd) in Patients With HER2-Overexpressing/Amplified Metastatic Colorectal Cancer | 2023 | ~80 (two dose levels) | Fam-trastuzumab deruxtecan 5.4 mg/kg or 6.4 mg/kg every 3 weeks | Randomized dose comparison | HER2-overexpressing/amplified (IHC 3+ or IHC 2+/ISH+) mCRC (extrapolated to SBA) | Confirmed ORR | cORR 37.8% (95% CI 27.3-49.2) in 5.4 mg/kg arm; 27.5% (95% CI 14.6-43.9) in 6.4 mg/kg arm. Majority IHC 3+ (78-85%). | Not fully reported in abstract. | Supports 5.4 mg/kg dosing; FDA approval in HER2-positive CRC extended to all solid tumors. | Journal of Clinical Oncology (abstract) |
| TRIDENT-1 | Repotrectinib in Patients with NTRK Fusion-Positive Advanced Solid Tumors | 2023 | 40 (TKI-naïve) + 48 (TKI-pretreated) | Repotrectinib 160 mg daily for 14 days then 160 mg BID | Single-arm | NTRK fusion-positive advanced solid tumors (including 3 CRC patients, 0 SBA) | Confirmed ORR | TKI-naïve: ORR 58%, 12-mo DOR 86%, 12-mo PFS 56%. TKI-pretreated: ORR 50%, 12-mo DOR 39%, 12-mo PFS 22%. Grade ≥3 AEs 51%. | Dizziness most common AE. | Repotrectinib approved for NTRK fusion-positive solid tumors. | Annals of Oncology |
| LIBRETTO-001 | Selpercatinib in Patients with RET Fusion-Positive Solid Tumors | 2022 | 41 efficacy-evaluable (including 1 SBA patient) | Selpercatinib 160 mg BID (≥50 kg) or 120 mg BID (<50 kg) | Single-arm | RET fusion-positive solid tumors (non-lung/non-thyroid), including SBA | ORR by independent review | Overall ORR 43.9% (95% CI 28.5-60.3). For SBA patient: complete response, DOR 24.5 months. Median PFS 13.2 months, median OS 18 months. | Common grade ≥3 AEs: hypertension, transaminitis. Treatment-related SAEs: drug-induced liver injury, fatigue, hypersensitivity. | FDA tissue-agnostic approval for RET fusion-positive solid tumors [172]. | Lancet Oncology |
| GARNET | Dostarlimab in Patients with Mismatch Repair-Deficient Solid Cancers | 2023 | 327 (23 with small-intestinal tumors) | Dostarlimab-gxly 500 mg IV every 3 weeks x4 then 1000 mg IV every 6 weeks | Single-arm | dMMR/MSI-H advanced solid tumors, including SBA (n=23) and POLE-mutated (n=11) | ORR | For small-intestinal cohort: ORR 39.1% (95% CI 19.7-61.5), 21.7% complete response rate. For overall efficacy population: median DOR not reached, median PFS 8.1 mo, median OS 31.6 mo. POLE-mutated (n=11): ORR 54.5%, PFS ≥1 year. | Immune-related AEs: hypothyroidism 6.9%, ALT increase 5.8%, arthralgia 4.7%. | FDA approval of dostarlimab for dMMR advanced solid tumors [148]. | JAMA Network Open |
| Phase II CAPEOX (Overman et al.) | Phase II Study of Capecitabine and Oxaliplatin for Advanced Adenocarcinoma of the Small Bowel and Ampulla of Vater | 2009 | 30 | CAPEOX (capecitabine 1000 mg/m2 BID days 1-14, oxaliplatin 130 mg/m2 day 1 every 21 days) | Single-arm | Advanced SBA and ampullary adenocarcinoma, first-line | ORR | ORR 50% (including 10% complete response). Median PFS and OS not reported for whole cohort, but median PFS 5.9 months and OS 17.3 months from another phase II (Horimatsu 2017) [128]. | Common AEs: neutropenia, thrombocytopenia, nausea, diarrhea, peripheral neuropathy, fatigue. | Established CAPEOX as a standard first-line option for metastatic SBA. | Journal of Clinical Oncology |
| Phase II FOLFIRI (Zaanan 2011) | Second-line Chemotherapy with Fluorouracil, Leucovorin, and Irinotecan (FOLFIRI regimen) in Patients with Advanced Small Bowel Adenocarcinoma After Failure of First-Line Platinum-Based Chemotherapy | 2011 | 28 | FOLFIRI | Single-arm | Advanced SBA after first-line platinum-based chemotherapy | ORR | ORR 20%, disease control rate 52%. Median PFS 3.2 months, median OS 10.5 months. Grade 3-4 toxicity in 48%. | Not specified. | Supports FOLFIRI as second-line therapy after oxaliplatin failure in metastatic SBA. | Cancer |
Clinical PearlsClick to collapse
- Pearl 1: Universal MMR/MSI testing is recommended for all newly diagnosed SBA patients, as dMMR/MSI-H is more common in SBA than CRC (up to 10-15%), has prognostic significance, and guides immunotherapy use [SBA-B].
- Pearl 2: For resectable SBA, adequate lymph node dissection (≥8 nodes) is critical for accurate staging and is associated with improved survival; <5 nodes for duodenal or <8 for jejunal/ileal primaries is considered high-risk [SBA-C, SBA-B].
- Pearl 3: Adjuvant therapy for SBA is largely extrapolated from colorectal cancer data; the BALLAD trial (phase III) is ongoing to address this question. For stage III pMMR/MSS, FOLFOX or CAPEOX for 3-6 months is recommended; for stage II with high-risk features (T4, positive margins, inadequate LN harvest, perforation), consider similar therapy [SBA-6].
- Pearl 4: For metastatic disease, biomarker testing (RAS, BRAF V600E, HER2, MMR/MSI, TMB, NTRK, RET, POLE/POLD1) is essential to identify actionable targets and guide therapy selection. TMB-high (>10 mut/Mb) is seen in 9-11% of SBA cases [SBA-8].
- Pearl 5: Checkpoint inhibitors (pembrolizumab, nivolumab, certain PD-1/PD-L1 agents) are recommended for dMMR/MSI-H advanced SBA for any line of therapy, with some agents included based on class effect from other tumor types [SBA-D 2 of 12].
- Pearl 6: Oxaliplatin neurotoxicity: discontinue oxaliplatin after 3-4 months (or sooner for unacceptable toxicity) while maintaining other agents; duloxetine/gabapentin only for pain component, not for numbness/tingling [SBA-D 3, SBA-F].
- Pearl 7: Radiation therapy is primarily reserved for duodenal primaries with positive margins after resection (sequential chemo/RT) or for locally unresectable disease as conversion strategy. For jejunal/ileal lesions, RT is generally not indicated [SBA-E].
- Pearl 8: Patients with Lynch syndrome, FAP, PJS, celiac disease, or Crohn's disease require genetic counseling and tailored surveillance due to elevated risk of metachronous SBA and other malignancies [SBA-1, SBA-F].