Bladder cancer incidence and mortality among men with and without castration therapy for prostate cancer - a nation-wide cohort study.

Background and purpose: Bladder cancer (BC) is a common malignancy in the Western World with men being diagnosed almost four times as often as women. The etiology of bladder cancer may involve sex hormones. Prostate cancer (PCa) patients treated with chemical castration, such as androgen deprivation therapy, or surgical castration, may therefore have a lower risk of developing bladder cancer.

Patients/material and methods: In a nation-wide population-based cohort study using national Danish registry data, we included a cohort of men with a first-time PCa diagnosis between 2002 and 2018 divided according to antihormonal treatment in the first year after PCa diagnosis and a comparison cohort consisting of 10 age-matched persons for each PCa patient. Each individual was followed from 1 year after PCa diagnosis until death or end of follow-up. We computed cumulative incidences (risk) and hazard ratios (HRs) for BC. In a second cohort analysis, we determined overall survival and BC-specific mortality, determined from date of BC diagnosis until death.

Results and interpretation: We included 48,776 PCa patients of whom 13,592 were treated with chemical castration, 2,261 with surgical castration, and 32,923 received no antihormonal treatment. The 5-year risk of BC for each PCa group was 1.1%, 0.7%, and 1.3%, respectively, corresponding to an adjusted HR of 1.13 (95% CI 0.98; 1.31), 0.95 (95% CI 0.62; 1.47), and 1.18 (95% CI 1.09; 1.28) compared to individuals without PCa. Patients receiving antihormonal treatment had a slightly lower incidence of BC compared to individuals without PCa, however, this was not supported by the HRs. The treatment, however, was not associated with overall survival.