Abstract
BACKGROUND: Few studies have systematically reported the relationship between the risk of breast cancer and family history of other cancers. This study was designed to systematically determine the relationship between breast cancer risk and family history of other cancers in first-degree relatives. METHODS: Between January 2006 and June 2011, 823 women diagnosed with breast cancer were included, and age-matched women diagnosed with benign breast disease were selected as controls. Family history of other cancers in first-degree relatives was recorded by trained reviewers. Multivariate logistic regression was applied to analyze the relationships. RESULTS: A family history of esophagus cancer (OR: 2.70, 95% CI: 1.11 - 6.57), lung cancer (OR: 2.49 95% CI: 1.10 - 5.65), digestive system cancer (OR: 1.79, 95% CI: 1.14 - 2.79) and any cancer (OR: 2.13, 95% CI: 1.49 - 3.04) in first-degree relatives was directly associated with increased breast cancer risk. In subgroup analysis, the risk of hormone receptor positive breast cancer was increased in subjects with a family history of lung cancer (OR: 3.37, 95% CI: 1.45 - 7.82), while the risk of hormone receptor negative breast cancer was increased in subjects with a family history of esophagus cancer (OR: 6.19, 95% CI: 2.30 - 16.71), uterus cancer (OR: 6.92, 95% CI: 1.12 - 42.89), digestive tract cancer (OR: 2.05, 95% CI: 1.03 - 4.10) and gynecology cancer (OR: 6.79, 95% CI: 1.46 - 31.65). Additionally, a significant increase in breast cancer was observed with a family history of digestive system cancer for subjects 50 y and younger (OR: 1.88, 95% CI: 1.03 - 3.43), not for subjects 50 y older (OR: 1.67, 95% CI: 0.86 - 3.25). CONCLUSIONS: Breast cancer aggregates in families with several types of cancer especially for digestive system cancer. The influence of a family history of other cancers seems more likely to be limited to hormone receptor negative breast cancer.