Radiation therapy for prostate cancer increases subsequent risk of bladder and rectal cancer: a population based cohort study.

PURPOSE: Pre-prostate specific antigen era series demonstrated an increased risk of bladder cancer and rectal cancer in men who received radiotherapy for prostate cancer. We estimated the risk of secondary bladder cancer and rectal cancer after prostate radiotherapy using a contemporary population based cohort.

MATERIALS AND METHODS: We identified 243,082 men in the Surveillance, Epidemiology and End Results database who underwent radical prostatectomy or radiotherapy for prostate cancer between 1988 and 2003. We estimated the incidence rate, standardized incidence ratio and age adjusted incidence rate ratio of subsequent bladder cancer and rectal cancer associated with radical prostatectomy, external beam radiotherapy, brachytherapy, and a combination of external beam radiotherapy and brachytherapy.

RESULTS: The relative risk of bladder cancer developing after external beam radiotherapy, brachytherapy and external beam radiotherapy-brachytherapy compared to radical prostatectomy was 1.88, 1.52 and 1.85, respectively. Compared to the general United States population the standardized incidence ratio for bladder cancer developing after radical prostatectomy, external beam radiotherapy, brachytherapy and external beam radiotherapy-brachytherapy was 0.99, 1.42, 1.10 and 1.39, respectively. The relative risk of rectal cancer developing after external beam radiotherapy, brachytherapy and external beam radiotherapy-brachytherapy compared to radical prostatectomy was 1.26, 1.08 and 1.21, respectively. The standardized incidence ratio for rectal cancer developing after radical prostatectomy, external beam radiotherapy, brachytherapy and external beam radiotherapy-brachytherapy was 0.91, 0.99, 0.68 and 0.86, respectively.

CONCLUSIONS: Men who receive radiotherapy for localized prostate cancer have an increased risk of bladder cancer compared to patients undergoing radical prostatectomy and compared to the general population. The risk of rectal cancer is increased in patients who receive external beam radiotherapy compared to radical prostatectomy. Patients should be counseled appropriately regarding these risks.