Adjuvant systemic therapy for small bowel gastrointestinal stromal tumor (GIST): Is there a survival benefit after R0 resection?

Background: The utility of adjuvant systemic therapy in small bowel gastrointestinal stromal tumor remains unclear. Methods: We queried the National Cancer Data Base for individuals having enterectomy to negative margins for small bowel gastrointestinal stromal tumor between 2010 and 2015. Subjects were categorized by tumor size (2.1–5 cm, 5.1–10 cm, >10 cm) and histologic grade (≤5 mitoses/50 high-power field and >5 mitoses/50 high-power field). Cox proportional hazard analysis was performed to evaluate the association between adjuvant therapy and overall survival. Results: One thousand five hundred fifty-nine patients met the inclusion criteria. On univariate comparison to resection alone, adjuvant therapy was associated with improved overall survival for individuals with high-grade tumors of intermediate and large size (85% vs 48%, P =.010; 75% vs 47%, P =.003) but not for those with high-grade tumors of small size or low-grade tumors of any size. On multivariable analysis adjusted for age, comorbid disease state, and tumor size, adjuvant therapy was independently associated with reduced risk of mortality for high-grade (hazard ratio 0.37, 95% confidence interval: 0.21–0.64) but not low-grade tumors. Conclusion: Adjuvant therapy after R0 resection for small bowel gastrointestinal stromal tumor should be administered after careful consideration of the size and grade of a patient's tumor.