Incidence of bladder cancer after radiation for prostate cancer as a function of time and radiation modality.

objectivesTo evaluate the risk of BlCa developing after radiation for PCa, stratified by ethnicity and follow-up duration.

methodsThe 1973-2011 surveillance, epidemiology and end results database was used to determine the observed and expected number of BlCa after PCa radiation. The adjusted relative risks (RRs) of developing BlCa were calculated for the various radiation modalities relative to no radiation, stratified by ethnicity and follow-up duration. BlCa characteristics were compared between patients with a history of prostate radiation and those without PCa.

resultsPCa was radiated in 346,429 men, 6401 of whom developed BlCa versus 2464 expected cases [SIR (95 % CI) of 2.60 (2.53-2.66)]. All radiation modalities were found to have an increased RR of developing BlCa after 10 years, with brachytherapy having a significantly higher RR than external beam radiation (EBRT) or combined EBRT and brachytherapy in Caucasian men and a significantly higher RR than EBRT in men of other/unknown ethnicity. Post-radiation BlCa, in particular that after brachytherapy, had higher grade (P = 0.0001) and lower stage (P = 0.0001) versus the general population.

conclusionsThe increased risk of BlCa after prostate radiation occurs predominantly after 10 years, regardless of ethnicity. The RR of developing BlCa after 10 years is significantly higher following brachytherapy than after EBRT or EBRT and brachytherapy. Bladder cancers after prostate radiation, especially after brachytherapy, are generally lower stage but higher grade than those in patients without PCa.