Prospective trial of adjuvant therapy after radical cystectomy for locally advanced bladder cancer: Analysis of the squamous cell carcinoma subgroup.

Abstract

524 Background: The role of adjuvant therapy after radical cystectomy (RC) is not well-defined for squamous cell carcinoma (SqCC) of the bladder. Several studies suggest limited efficacy for chemo while adjuvant RT improved disease-free survival (DFS) vs. observation in a previous trial. In this study, we report a post-hoc subgroup analysis of SqCC to compare adjuvant therapies. We hypothesized that adjuvant RT would improve DFS vs. chemo for locally advanced bladder cancer (LABC) (≥pT3N0-N+). Methods: A randomized phase III trial was opened to compare adjuvant RT vs. sandwich chemo+RT after RC for LABC at the NCI in Cairo. A 3rd arm, adjuvant chemo, was added later. Bladder cancer patients ≤70 y/o with ≥1 of the following (pT3b/pT4a, grade 3, or pN+) with negative margins after RC were eligible. RT was delivered to the pelvis with 3D conformal RT (45Gy in 1.5Gy BID). Chemo+RT included 2 cycles of gemcitabine/cisplatin before & after RT. Chemo alone included gem/cis x 4. Primary & secondary endpoints were DFS and overall survival (OS). Results: 198 patients were enrolled. 82 (41%) had SqCC & 77 had ≥pT3N0-N+ disease and were analyzed (34 RT, 27 chemo+RT, & 16 chemo). Median age was 53. Median F/U was 20 months (1-127 months). The RT vs chemo arms were well-balanced except for number of nodes removed (mean 12 vs. 9, p=0.05). On univariable analysis, RT was not significantly associated with DFS [HR 0.56 (95%CI 0.26-1.21), p=0.14]. On multivariable analysis, only pN+ was significant. 2-yr DFS was 60% for RT & 43% for chemo (log-rank p=0.13). OS was improved with RT (2-yr OS 71% vs. 43%, p=0.04). There was one death during treatment (chemo-related). There was no significant difference in DFS or OS for RT vs. chemo+RT with 2-yr DFS of 59% & 55% (p=0.65) & 2-yr OS of 67% & 74% (p=0.16). Conclusions: On post-hoc analysis, RT for locally advanced bladder SqCC was associated with significantly improved OS vs. adjuvant chemo. We hypothesize that the inferior OS with chemo was due to increased toxicity & limited efficacy. There was no difference in outcomes for RT vs. chemo+RT. Adjuvant RT should be a standard option for ≥pT3 SqCC of the bladder after RC. Alternative chemo agents for SqCC should be explored. Clinical trial information: NCT01734798.