Risk of genitourinary malignancies after cancer of the prostate.

The risk of second malignancies was evaluated in all men in metropolitan Atlanta who were initially diagnosed as having prostate cancer between January 1, 1975 and December 31, 1982. The cohort of 3675 men was observed through the end of calendar year 1984, yielding a total of 11,916 man-years of observation. Within this population 220 second cancers were diagnosed at sites other than the prostate as compared with 181.2 cancers expected based upon incidence rates for the local general population. Excesses of second malignancies were found in the urethra, kidney and bladder, as well as for melanoma of the skin. The increased risk of second neoplasms was generally greater in men younger than 70. The associated genitourinary malignancies tended to occur within 3 years of the prostatic cancer. Although increased clinical surveillance of this population could explain some of the observed excess of second cancers, these findings also are consistent with multiple cancers arising from shared etiologic factors.