No survival benefit from adjuvant chemotherapy in high-risk stage II small intestinal adenocarcinoma after surgery: a population-based long-term survival analysis.

BACKGROUND

The benefit of adjuvant chemotherapy in small intestinal adenocarcinoma (SA) remains poorly defined due to the rarity of the disease and the lack of randomized trials. This study aimed to evaluate the survival benefit of adjuvant chemotherapy based on pathological stage and primary tumor site in patients with jejunal and ileal adenocarcinoma.

METHODS

Data of patients with stages I-III jejunal or ileal adenocarcinoma who underwent curative resection between 2004 and 2022 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Patients were categorized into adjuvant chemotherapy (+) and adjuvant chemotherapy (-) groups. To address potential confounding and imbalance in baseline characteristics, propensity score matching (PSM) was employed. Survival differences were assessed using Kaplan-Meier analysis and Cox proportional hazards models.

RESULTS

Among 896 eligible patients, adjuvant chemotherapy was associated with improved overall survival (OS) in the overall cohort (5-year OS: 53.3% vs. 52.1%, P=0.02), but not cancer-specific survival (CSS). Multivariable analysis identified adjuvant chemotherapy as an independent prognostic factor for OS [hazard ratio (HR) =0.56; 95% confidence interval (CI): 0.45-0.69; P<0.001] but not for CSS. Stage-stratified analysis revealed that the survival benefit was confined to stage III patients, with adjuvant chemotherapy significantly improving both OS and CSS (P<0.001), which was confirmed by PSM (OS: HR =0.46; CSS: HR =0.54; both P<0.001). In contrast, adjuvant chemotherapy provided no significant survival benefit for stage I or II patients, even those with stage II high-risk features (T4 stage, <8 lymph nodes examined, poor tumor differentiation).

CONCLUSIONS

This population-based analysis provides evidence supporting the use of adjuvant chemotherapy specifically in patients with lymph node-positive (stage III) jejunal or ileal adenocarcinoma. For patients with stages I-II disease, our findings do not support the routine use of adjuvant chemotherapy, even in the presence of stage II high-risk pathological features.