The characteristics of bladder cancer after radiotherapy for prostate cancer

Prostate radiotherapy (RT) has been associated with an increased risk of bladder cancer (CaB). However it is unknown how prior RT affects the stage, grade, and histology of secondary CaB. While irradiated patients have adverse surgical outcomes, how RT affects survival is also unknown. We sought to determine how RT for prostate cancer (CaP) affects the characteristics and outcomes of secondary CaB.

A retrospective review of 275,200 cases of clinically localized CaP submitted to the Surveillance, Epidemiology, and End Results (SEER) database between 1988 and 2007 was performed. CaP treatment was stratified by radical prostatectomy (RP) alone, RT, or RP + RT. Diagnosis of CaB at least 1 year after CaP, and CaB death were the primary outcomes. The stage, grade, and histology of CaB of patients exposed to RT or RP were compared. A competing risks multivariable survival analysis was performed to determine the effect of RT on CaB-specific mortality.

CaP patients treated with any RT were 1.70 times as likely to develop CaB (95% CI 1.57-1.86, P < 0.001) compared with RP alone. CaB in men who had RT were more likely non-urothelial (6.4% vs. 3.8%, P = 0.004), trigonal (6.9% vs. 5.4%, P = 0.012), and carcinoma in-situ (CIS) (9.2% vs. 7.0%, P < 0.001) compared with RP. RT increased CaB-specific mortality (HR = 1.30, P = 0.02), which remained significant when adjusted for CaB features (HR = 1.28, P = 0.05).

Patients with localized CaP treated with RT have a higher risk of CaB. CaB after RT is more likely to be located at the trigone and contain CIS. Patients with CaB after RT have decreased cancer-specific survival compared with those undergoing RP alone.