ABSTRACT
INTRODUCTION: Low certainty exists on how bladder cancer (BCa) after pelvic radiotherapy (RT) differs from BCa in radiation-naive patients from a histopathological and clinical perspective. This study aims to compare histopathological features of bladder tumors between patients with previous RT for prostate cancer (PCa) and radiation-naive patients using single-institutional data and to estimate relapse-free survival (eRFS) and cystectomy-free survival (eCFS) in both groups. MATERIALS AND METHODS: Comparative study in adult men diagnosed with BCa in Hospital Italiano de Buenos Aires, Argentina, between January 2015 and December 2020. Included patients were categorized as previously irradiated for PCa or radiation-naive. PRIMARY OUTCOME: differences in prevalence of aggressiveness features of bladder tumors (variant histology; high-grade tumors; muscle-invasive disease; criteria compliance for high or very-high risk of progression) between irradiated and radiation-naive patients at diagnosis of BCa. SECONDARY OUTCOMES: differences in eRFS and eCFS between groups. RESULTS: In total, 34 and 291 patients were included in the Irradiated and Radiation-naive groups, respectively. Mean age at the time of diagnosis of BCa was 72.7 years (CI 95% 71.6-73.8). Median follow-up of the overall cohort was 25 months (IQR 11-45.5). Concerning primary outcomes, no statistical differences were found except for a higher prevalence of low-grade tumors between irradiated patients and high-grade tumors between radiation-naive patients (P 0.018). Regarding secondary outcomes, prior RT did not increase neither eRFS nor eCFS in both univariate and multivariate analysis. CONCLUSIONS: BCa after RT for PCa has similar histological features and cystectomy free-survival compared to BCa in a radiation-naive population. For patients with non-muscle invasive BCa arising after prostate RT, the risk of recurrences appears to be similar to non-irradiated patients.