Risk of multiple primary cancers in prostate cancer patients in the Detroit metropolitan area: a retrospective cohort study.

Abstract

Patterns of excess risk for second primary cancers (SPC) in prostate cancer patients have been observed for urinary bladder, other sites in the urinary tract, and hematolymphopoietic tissues in several, but not all, previously reported cohort studies. The risk of SPC was evaluated in 9,794 Detroit metropolitan-area men originally diagnosed with carcinoma of the prostate during 1973-1982. The cohort was assembled using Detroit Surveillance, Epidemiology, and End Results (SEER) Registry data and followed until December 31, 1993. The observed number of SPC of all sites was similar to the expected number in the cohort. A significant excess of invasive SPC of the urinary bladder [Standardized incidence ratio (SIR) = 1.57; 95% CI, 1.34-1.83] was observed in this cohort, but after excluding the first 2 months after prostate cancer diagnosis, the excess (SIR = 1.06) was no longer statistically significant. The cumulative proportion of patients with prostate cancer who developed bladder cancer during a follow-up interval of 20 years was 5.5% (95% CI, 4.1-6.9%). The patients who received first-course radiation treatment were observed to be at increased risk for bladder SPC (all stages; SIR = 1.49; 95% CI, 1.07-2.02) when compared to the Detroit-area male population. These results underscore the importance of continuing medical surveillance for urinary bladder second primary cancers in patients with prostate cancer, but are reassuring in that the magnitude of relative and absolute risks does not suggest deterring adverse effects of radiation treatment or intrinsic risks for neoplasms in other organs or tissues.