Early onset and familial predisposition to prostate cancer significantly enhance the probability for breast cancer in first degree relatives

Genetic predisposition accounts for greater than or equal to 10% of all can cer of the prostate (CaP) and is therefore considered a major risk factor, together with age and ethnic origin. Several epidemiological studies have s uggested that familial clustering of Cap may be associated with an increase d frequency of breast and other cancers among relatives. In order to correl ate the incidence of Cap with prevalence of breast and other cancers, we ha ve performed uni- and multi-variate analyses on 691 complete pedigrees incl uding probands, who were consecutive patients with confirmed Cap treated in three French urological departments. We have shown a significantly higher risk (RR = 2.3, p = 0.01) to develop breast cancer in families with multipl e than in those with a single Cap. Risk of observing other types of cancer within these families was not significant. We then calculated the breast ca ncer risk in early onset prostate cancer families, and observed a relative risk that is even more significant (RR = 5.5, p = 0.002). Furthermore, the risk was >30 times that a proband's mother have breast cancer if Cap occurr ed below 55 years of age, rather than after 75 years (p = 0.003). This stud y has therefore shown for the first time, the relatively high penetrance fo r breast cancer in relatives of early onset Cap patients. Int. J. Cancer 86 :883-887, 2000. (C) 2000 Wiley-Liss, Inc.