Family history of cancer and risk of breast cancer.

The relationship between breast cancer risk and family history of cancer in first-degree relatives was investigated using data from a multicentric case-control study conducted in Italy between June 1991 and April 1994 on 2,569 women aged less than 75 years, with histologically confirmed incident breast cancer, and 2,588 control women admitted to hospital for acute, non-neoplastic, non-gynaecological conditions. Relative to women with no history, those with a family history of breast cancer had an odds ratio (OR) of 2.4 [95% confidence interval (CI) 1.9-3.0], and those with family history of intestinal cancer had an OR of 1.3 (95% CI 1.0-1.7). No significant relations emerged between breast cancer risk and family history of prostate (OR 1.1), ovarian (OR 1.3), cervical or endometrial (OR 1.2) or other cancers, except gallbladder (OR 8.6). The OR for family history of any type of cancer except breast cancer was 1.1. For family history of breast cancer the ORs were similar across strata of age of the proband, being 2.4 below age 45, 2.2 at age 45-59 and 2.7 above age 60, and whether the relative affected was the mother, sister(s) or both, while the risk appeared higher if the age at onset of breast cancer in the relative was lower than 40 years (OR 3.5), rather than higher (OR 2.2). Thus, our results, based on the investigation of all neoplasms in first-degree relatives, confirm that breast cancer risk is increased in women with a family history of breast cancer, while there was no material association with family history of cancer in general, excluding breast cancer.