Patients with prostate cancer who undergo radiation treatment, especially brachytherapy, may be at increased risk of bladder cancer more than 10 years later, according to the results of a new study presented at the American Urological Association annual meeting. The study showed that bladder tumors that do develop are generally lower stage but higher grade.

The researchers analyzed data from the 1973-2011 Surveillance, Epidemiology and End Results database and found that bladder cancer developed in 6,401 o the 346,429 men who received radiotherapy for prostate cancer. The number was 2.6 higher than the expected incidence of bladder cancer in the general population. All radiation treatment modalities were associated with a higher relative risk of bladder cancer after 10 years, with the most significant risk for brachytherapy alone (compared to external-beam radiation therapy [EBRT] or EBRT plus brachytherapy).

In adjusted analyses, brachytherapy was associated with a 3.5-fold, 2.9-fold, and 5.5-fold increased risk of bladder cancer after 10 years in Caucasians, African Americans, and other/unknown races, respectively, compared to men without a history of prostate cancer.