Effectiveness of adjuvant radiotherapy after radical cystectomy for locally advanced bladder cancer.

Abstract

484 Background: Local-regional failure (LF) for locally advanced bladder cancer (LABC) after radical cystectomy (RC) is common even with chemo and is associated with high morbidity/mortality. Adjuvant radiotherapy (adjRT) can reduce LF and may enhance overall survival (OS) but has no defined role. We hypothesized that the addition of adjRT would improve OS in LABC in a large multi-institutional cohort. Methods: We identified ≥pT3 pN0-3, M0 LABC pts in the NCDB diagnosed in 2004 – 2013 who underwent RC +/- adjRT. AdjRT cohort included pts treated to ≥40Gy to the pelvis within 1 yr of diagnosis. Propensity matching was performed to match RC pts who received adjRT vs. those who did not. OS was calculated using Kaplan-Meier. Factors significant on univariate analysis were entered into Cox proportional hazards regression model to identify predictors of OS. Results: 15,246 RC pts were identified, with 450 (3.0%) receiving adjRT. Median OS was 23.0 mo (95% CI, 22.4-23.6) for RC vs. 19.7 mo (95% CI, 17.7-21.7) for adjRT [Log-rank P = 0.002; Wilcoxon P = 0.862]. Propensity score matching on demographic, clinical, & treatment variables yielded 742 pts (371 in each group). In the matched cohort, OS was 17.1 mo [95%CI, 14.5 - 19.6] for RC vs. 20.1 mo [95% CI, 17.8– 22.5] for adjRT [Log-rank P = 0.044]. On MVA in the matched cohort, factors predictive of OS were sex, pT stage, pN+ status, surgical margin status, number of nodes removed, adjRT, & chemo (p < 0.01 for all). On MVA of subgroups, adjRT was associated with significantly improved OS in pts with positive margins [HR 0.55 (95% CI, 0.43 – 0.71), P < 0.001], pN+ disease [HR 0.62 (95% CI, 0.49 – 0.79), P < 0.001], & pT4 disease [HR 0.68 (95% CI, 0.55 – 0.85), P = 0.001]. In MVA of pts with urothelial carcinoma (N = 578), adjRT remained associated with improved OS in pts with positive margins [HR 0.57 (95% CI, 0.43 – 0.76), P < 0.001], pN+ disease [HR 0.65 (95% CI, 0.50 – 0.86), P = 0.002], & pT4 disease [HR 0.68 (95% CI, 0.54 – 0.85), P = 0.001]. Conclusions: In this observational study, adjRT was associated with improved OS in LABC. While the data should be interpreted cautiously, these results lend support to the use of adjRT in selected pts with LABC, regardless of histology. Prospective trials of adjRT are warranted.