HEREDITARY AND FAMILIAL OVARIAN-CANCER IN SOUTHERN ONTARIO

Background. Hereditary ovarian cancer may be site specific or may appear in combination with breast cancer or other cancers in a family. The most common hereditary form is the breast-ovarian cancer syndrome. It is estimated that in 100% of these families, there is linkage to a cancer susceptibility gene on chromosome 17q, BRCA1. Methods. A positive family history of breast or ovarian cancer was reported for 71 of 450 unselected cases of ovarian cancer identified in Southern Ontario. Detailed pedigrees were completed by telephone interview for 48 of the 71 subjects. Results. Nine families were identified with five or more cases of breast or ovarian cancer, 14 families with four cases of cancer, and eight families with three cases. Breast cancer appeared in 80% of the ovarian cancer families. There were 81 healthy first-degree female relatives of the cancer cases considered to be at high risk for ovarian cancer. Conclusions. It is feasible to use a simple questionnaire on all incident cases of ovarian cancer in a population to identify families with potential hereditary breast-ovarian cancer. Two point nine percent to 6.9% of cases of ovarian cancer appear to be inherited; the majority of the families also will have an excess number of cases of breast cancer.