Adjuvant radiotherapy improves long-term survival after resection for gallbladder cancer A population-based cohort study

Background: Data supporting routine use of adjuvant radiotherapy (RT) compared to without RT (noRT) for gallbladder cancer (GBC) is unclear. This study aimed to determine whether RT improves long-term survival following resection for GBC. Methods: Patients receiving resection for GBC followed by RT from 2004 to 2016 were identified from the National Cancer Database (NCDB). Patients with survival <6 months were excluded to account for immortal time bias. Propensity score matching (PSM) and Cox regression was performed to account for selection bias and analyze impact of RT on overall survival. Results: Of 7514 (77%) noRT and 2261 (23%) RT, 2067 noRT and 2067 RT patients remained after PSM. After matching, RT was associated with improved survival (median: 26.2 vs 21.5 months, p < 0.001), which remained after multivariable adjustment (HR: 0.82, CI_95%: 0.76–0.89, p < 0.001). On multivariable interaction analyses, this benefit persisted irrespective of nodal status: N0 (HR: 0.84, CI_95%: 0.77–0.93), N1 (HR: 0.77, CI_95%: 0.68–0.88), N2/N3 (HR: 0.56, CI_95%: 0.35–0.91), margin status: R0 (HR: 0.85, CI_95%: 0.78–0.93), R1 (HR: 0.78, CI_95%: 0.68–0.88) and use of adjuvant chemotherapy (AC) (HR: 0.67, CI_95%: 0.57–0.79). Benefit with RT were also seen in patients with T2 - T4 disease and in patients undergoing simple and extended cholecystectomy. Conclusion: RT following resection was associated with improved survival in this study, even in margin-negative and node-negative disease. These findings may suggest addition of RT into multimodality therapy for GBC.