Familial Associations Between Prostate Cancer and Other Cancers.

Prostate cancer (PCa) has a large familial component, but understanding of its genetic basis is fragmentary. Breast cancers may be associated with PCa, but whether this is true for other tumor types is poorly established. We used a novel approach to study familial associations of any type of cancer with PCa. We assessed the relative risk (RR) for all types of tumors as a function of the number of first-degree relatives diagnosed with PCa. We hypothesized that for a familial association to be real, the RR for a given type of cancer should increase with the number of PCa diagnoses. In families with multiple PCa patients, significantly increased risks were observed for female breast cancer (RR 1.37 for families with three men with PCa), kidney cancer (RR 2.32), nervous system tumors (RR 1.77; RR 2.40 when PCa was diagnosed before age 70 yr), and myeloma (RR 2.44; RR 6.29 when PCa was diagnosed before age 70 yr). Some evidence of association was also found for melanoma (RR 1.82) and endocrine tumors (RR 2.18). The consistency and magnitude of the effects suggest that familial PCa is genetically associated with breast, kidney, and nervous system tumors and myeloma. This suggestion has implications for clinical counseling and design of genetic studies.

PATIENT SUMMARY: It is known that prostate cancer runs in families, but it is not known whether other cancers are common in such families. We showed that at least breast, kidney, and nervous system tumors and myeloma occur more often than by chance.