A 20-Year Real-World Study of Small Bowel Cancers: Histologic Subtypes, Clinical Features, and Survival Implications

Background: Small-bowel cancers (SBCs) are rare, histologically diverse malignancies with limited data from Asian populations. This study aimed to describe histological subtype distribution, clinical features, survival outcomes, and prognostic factors in SBCs over a 20-year period. Methods: We retrospectively reviewed patients diagnosed with SBC at a tertiary referral center in Southern Thailand (2005-2024). Clinical, pathological, and radiological data were analyzed by histologic subtype. Results: A total of 158 patients were included: adenocarcinoma (81.0%), gastrointestinal stromal tumor (GIST, 5.7%), well-differentiated neuroendocrine tumor (NET, 5.7%), other sarcomas (5.1%), and poorly differentiated neuroendocrine carcinoma (NEC, 2.5%). Adenocarcinoma predominantly affected older patients and frequently presented with advanced-stage disease and poor performance status, whereas NET and NEC occurred in younger patients typically at early NET and metastatic NEC stages. Median overall survival (OS) varied by subtype: adenocarcinoma (8.3 months), GIST (63.6 months), NEC (8.9 months), NET (not reached), and other sarcomas (9.8 months). Five-year OS rates were 14.0%, 55.6%, 0%, 88.9%, and 18.8%, respectively. Eastern Cooperative Oncology Group performance status ≥2, duodenal location, and metastatic disease were independently associated with worse OS. Conclusions: SBCs display distinct clinical and prognostic profiles by subtype. Overall prognosis remained poor, underscoring the need for earlier detection and subtype-specific management.