THE CALCULATION OF BREAST-CANCER RISK FOR WOMEN WITH A FIRST DEGREE FAMILY HISTORY OF OVARIAN-CANCER

Recent linkage analyses demonstrate the strength of the genetic associ ation between breast and ovarian cancer in some families. These findin gs highlight the importance of considering a woman's family history of ovarian cancer in the calculation of her risk of breast cancer. In th is study, data on breast and ovarian cancer from the Cancer and Steroi d Hormone Study, a large, population-based, case-control study conduct ed by the Centers for Disease Control, are used to calculate age-speci fic and cumulative risks of developing breast cancer for a woman with a first degree family history of ovarian cancer. These risks are calcu lated using maximum likelihood estimates from an autosomal dominant ge netic model fit previously to the observed age-specific recurrence dat a of breast cancer among first degree relatives of the breast cancer c ases and controls in these data as well as from genotype-specific esti mates of lifetime ovarian cancer risk derived from this model. Under t his model, the lifetime risk of developing breast cancer for a woman w ith one or two first degree relatives affected with ovarian cancer is estimated to be approximately 13% and 31%, respectively. A woman with one first degree relative affected with ovarian cancer and one first d egree relative affected with breast cancer has an estimated risk of 40 percent of developing breast cancer by age 79 years if the relative w ith breast cancer was diagnosed in her thirties. This risk decreases w ith increasing age of onset of the relative affected with breast cance r.