ABSTRACT
Twelve pedigrees showing a clustering of breast and ovarian cancers among female relatives were analyzed. Ninety-one female relatives of the 12 subject probands were found to have breast cancer (n 60), ovarian cancer (n 28) or both (n 3). The age of cancer diagnosis was typically earlier (50 years for breast cancer and 52.4 years for ovarian cancer) among affected individuals than in the general population. Mother to daughter and father to daughter transmission of elevated breast and ovarian cancer risk was observed in the 12 pedigrees studied. Excluding the proband or index case, the estimated cumulative risk of breast and ovarian cancer to daughters of affected mothers was 46% for the age interval 20-80 years, suggesting that affected mothers in these pedigrees transmit a cancer susceptibility gene to half of their daughters. In addition there was evidence for male transmission of breast and ovarian susceptibility in eight sibships.
