A Propensity Analysis Comparing Definitive Chemo-Radiotherapy for Muscle-Invasive Squamous Cell Carcinoma of the Bladder Vs. Urothelial Carcinoma of the Bladder Using the National Cancer Database

Introduction: Squamous cell carcinoma (SqCC) is the second most common histology of primary bladder cancer, but still very limited information is known about its treatment outcomes. Most bladder cancer trials have excluded SqCC, and the current treatment paradigm for localized SqCC is extrapolated from results in urothelial carcinoma (UC). In particular, there is limited data on the efficacy of definitive chemo-radiotherapy (CRT). In this study, we compare overall survival outcomes between SqCC and UC patients treated with definitive CRT. Materials/methods: We queried the National Cancer Database (NCDB) for muscle-invasive (cT2-T4 N0 M0) bladder cancer patients diagnosed from 2004 to 2013 who underwent concurrent CRT. Propensity matching was performed to match patients with SqCC to those with UC. OS was analyzed using the Kaplan-Meier survival method, and the log-rank test and Cox regression were used for analyses. Results: 3332 patients met inclusion criteria of which 79 (2.3%) had SqCC. 73.4% of SqCC patients had clinical T2 disease compared to 82.5% of UC patients. Unadjusted median OS for SqCC patients was 15.6 months (95% CI, 11.7-19.6) versus 29.1 months (95% CI, 27.5-30.7) for those with UC (P < 0.0001). On multivariable analysis, factors associated with worse OS included: SqCC histology [HR: 1.53 (95% CI, 1.19-1.97); P = 0.001], increasing age [HR: 1.02 (95% CI, 1.02-1.03); P < 0.0001], increasing clinical T-stage [HR: 1.21 (95% CI, 1.13-1.29); P < 0.0001], and Charlson-Deyo comorbidity index [HR: 1.26 (95% CI, 1.18-1.33); P < 0.0001]. Seventy-seven SqCC patients were included in the propensitymatched analysis (154 total patients) with a median OS for SqCC patients of 15.1 months (95% CI, 11.1-18.9) vs. 30.4 months (95% CI, 19.4-41.4) for patients with UC (P = 0.013). Conclusions: This is the largest study to-date assessing survival outcomes for SqCC of the bladder treated with CRT. In this study, SqCC had worse overall survival compared to UC patients. Histology had a greater impact on survival than increasing T-stage, suggesting that histology should be an important factor when determining a patient's treatment strategy and that treatment intensification in this subgroup may be warranted. (C) 2019 The Authors. Published by Elsevier B.V. on behalf of European Society for Radiotherapy and Oncology.