Survival benefit with adjuvant radiotherapy after resection of distal cholangiocarcinoma: A propensity-matched National Cancer Database analysis.

BACKGROUND: No convincing evidence for the benefit of adjuvant radiotherapy (RT) following resection of distal cholangiocarcinoma (dCCA) exists, especially for lower-risk (margin- or node-negative) disease. Hence, the association of adjuvant RT on survival after surgical resection of dCCA was compared with no adjuvant RT (noRT). METHODS: Using National Cancer Database data from 2004 to 2016, patients undergoing pancreatoduodenectomy for nonmetastatic dCCA were identified. Patients with neoadjuvant RT and chemotherapy and survival <6 months were excluded. Propensity score matching was used to account for treatment-selection bias. A multivariable Cox proportional hazards model was then used to analyze the association of adjuvant RT with survival. RESULTS: Of 2162 (34%) adjuvant RT and 4155 (66%) noRT patients, 1509 adjuvant RT and 1509 noRT patients remained in the cohort after matching. The rates of node-negative disease (N0), node-positive disease (N+), and unknown node status (Nx) were 39%, 51%, and 10%, respectively. After matching, adjuvant RT was associated with improved survival (median, 29.3 vs 26.8 months; P < .001), which remained after multivariable adjustment (HR, 0.86; 95% CI, 0.80-0.93; P < .001). Multivariable interaction analyses showed this benefit was seen irrespective of nodal status (N0: HR, 0.77; 95% CI, 0.66-0.89; P < .001; N+: HR, 0.79; 95% CI, 0.71-0.89; P < .001) and margin status (R0: HR, 0.58; 95% CI, 0.50-0.67; P < .001; R1: HR, 0.87; 95% CI, 0.78-0.96; P = .007). Stratified analyses by nodal and margin status demonstrated consistent results. CONCLUSIONS: Adjuvant RT after dCCA resection was associated with a survival benefit in patients, even in patients with margin- or node-negative resections. Adjuvant RT should be considered routinely irrespective of margin and nodal status after resection for dCCA. LAY SUMMARY: Adjuvant radiotherapy after resection of distal cholangiocarcinoma was associated with a survival benefit in patients, even in patients with margin-negative or node-negative resections. Adjuvant radiotherapy should be considered routinely irrespective of margin and nodal status after resection of distal cholangiocarcinoma.