Family history of malignancies and risk of breast cancer: prospective data from the Shanghai women's health study.

A population-based cohort study was conducted in Shanghai, China, to investigate the relationship between family cancer history in first-degree relatives and risk of breast cancer. A total of 570 newly diagnosed breast cancer patients were identified from the cohort of 73,222 women during the follow-up period. Breast cancer risk was elevated (RR = 1.74, 95% CI: 1.10-2.73) for those with a family history of breast cancer and the risk was stronger for women who were younger than 55 years (RR = 2.07, 95% CI: 1.17-3.64). In addition, a significantly increased risk was observed for women with a family history of leukemia (RR = 2.06; 95% CI: 1.02-4.15) and among younger women, those who reported having a family history of any cancer (RR = 1.41, 95% CI: 1.10-1.82), lung cancer (RR = 1.72, 95% CI: 1.12-2.65), and esophageal cancer (RR = 2.99, 95% CI: 1.62-5.51). This cohort study suggests that, as previously observed in high risk populations, family history plays an important role in breast cancer also in a low risk population. The link between breast cancer risk and family history of cancers of the lung and esophagus, as well as leukemia, warrants further investigation.