Risk of cancer in relatives of prostate cancer probands

It is estimated that there will be more than 244,000 new prostate cancer cases diagnosed and that more than 40,000 men will die of this disease during 1995. Evidence exists for a hereditary predisposition to prostate cancer, but the proportion of cases attributable to the inheritance of a specific gene or genes is not large. Some hereditary cancer syndromes involve more than one tumor site, and some studies have reported a familial association between prostate cancer and other cancers. The presence of other cancers in prostate cancer families may indicate a specific type of hereditary predisposition.

We studied families that were selected because of the presence of prostate cancer to determine whether hereditary prostate cancer is associated with cancers at other sites and possibly with other heritable cancer syndromes.

Data from two distinct study populations were studied retrospectively. The first population consisted of 690 case patients undergoing radical prostatectomy who were not selected for family history of prostate cancer and 640 control subjects who were the spouses or female companions of the case patients. The second population consisted of 75 multiplex families (i.e., families with multiple cases of prostate cancer) referred because they fulfilled the criteria for hereditary prostate cancer. A comparison between case and control populations for the occurrence of 14 aggregated groups of cancer was performed. Data were analyzed using Poisson regression, and relative risks (RRs) and their 95% confidence intervals (CIs) were calculated.

Brothers and fathers of prostate cancer probands have a statistically significant higher risk of prostate cancer than the male first-degree relatives of control subjects (RR = 1.76; 95% CI = 1.28-2.43). Therefore, the risk for prostate cancer is 76% higher among first-degree relatives of prostate cancer patients compared with first-degree relatives of control subjects. This higher risk was not modified by an occurrence of breast cancer in the pedigree. Also, a statistically significant higher risk was found for tumors of the central nervous system in hereditary families (RR = 3.02; 95% CI = 1.08-8.41). Statistically significant higher risks of cancer at other major sites, such as breast, ovary, or endometrium were not observed in these families.

Even among families that were specifically selected because of the presence of prostate cancer, risks for cancer at other sites appeared not to be increased. Therefore, hereditary prostate cancer appears to be a relatively site-specific disease, and it does not seem to be a part of other hereditary cancer syndromes.