Small bowel adenocarcinoma in Crohn’s disease: a systematic review and meta-analysis of the prevalence, manifestation, histopathology, and outcomes

Background and aims: Small bowel adenocarcinoma (SBA) is a rare neoplasm that is associated with Crohn’s disease (CD). This study aims to quantify the prevalence of CD-SBA, review the current evidence of histopathology and molecular analysis findings, and identify the clinical presentation and outcomes of CD-SBA. Methods: Electronic databases Medline and Embase were searched for articles describing SBA in inflammatory bowel disease patients. The histopathology, molecular analysis findings, clinical presentation, prevalence, and outcomes of CD-SBA were extracted, and results were pooled with random effects. Results: In total, 33 articles were included in the analysis. Prevalence of SBA was 1.15 (CI: 0.31–2.33) per 1000 CD patients. Only 11% (CI: 0.04–0.21) of CD-SBA patients had observable radiological features. CD-SBA was most commonly found in the ileum (84%), diagnosed at stage 2 (36%), with main presenting complaints including obstruction, weight loss, and abdominal pain. Significant histopathological findings included adjacent epithelial dysplasia, and an equal distribution of well-differentiated (49%) and poorly differentiated subtypes (46%). Most prevalent genetic mutation was KRAS mutation (18%), followed by mismatch repair deficiency (9.7%). The 5-year overall survival for CD-SBA patients was 29% (CI: 0.18–0.41), and 33% (CI: 0.26–0.41) for de novo SBA. No statistically significant increase in risk for CD-SBA was noted for treatment with thiopurines, steroids, and 5-ASA. Conclusion: Our meta-analysis found the prevalence of CD-SBA to be 1.15 per 1000 CD patients. The 5-year overall survival for CD-SBA was poor. The presenting symptoms were non-specific, and therefore the diagnosis requires a high index of suspicion.