Family history of breast, ovarian and endometrial cancer and risk of breast cancer.

The relationship between family history of breast, ovarian and endometrial cancer and risk of breast cancer was analysed using data from a case-control study of breast cancer conducted in the greater Milan area, Northern Italy. The cases studied were 3415 women (median age 52 years, range 23-74) who had histologically confirmed breast cancer diagnosed within the year preceding the interview. The controls were 2916 women (median age 54 years; range 21-74) in hospital for a spectrum of acute illnesses excluding gynaecological, hormonal or neoplastic conditions. A total of 375 cases (11.0%) and 128 controls (4.4%) reported a history of breast cancer in first degree relatives. Compared with women with no family history of breast cancer, the RR was 2.7 (95% confidence interval [CI] : 2.2-3.3) in those with one first degree relative affected and 2.8 (95% CI : 1.3-5.7) in those with two or more affected relatives. In comparison with women without family history of ovarian cancer the RR of breast cancer was 1.4 (95% CI : 0.9-2.3) for those reporting one or more first degree relatives with ovarian cancer. However, the multivariate estimate for family history of ovarian cancer, including a term for familial breast cancer, decreased to 0.8 (95% CI : 0.5-1.4). The risk of breast cancer was similar in women reporting a family history of breast cancer (RR = 2.2) and in those reporting a family history of both breast and ovarian cancer (RR = 2.5), in comparison with women reporting no family history of breast and/or ovarian cancer.(ABSTRACT TRUNCATED AT 250 WORDS)