MedWire News: A family history of any sort of malignancy increases a woman's risk for developing breast cancer, especially if she has first-degree relatives with leukemia, esophageal, lung, or breast cancer, a study has found.
The risk was greatest in women with early onset breast cancer whose parents rather than siblings were affected by a malignancy, indicating that inherited genetic susceptibility rather than shared environmental factors play an important role in the link between breast and other cancers, Yawei Zhang (Yale University, New Haven, Connecticut, USA) and colleagues claim.
Many previous studies have shown that women with a first-degree relative with breast cancer have approximately double the risk for the disease, although the relationship between family history of other malignancies and breast cancer is unclear.
In the present study, the researchers recruited 73,222 women who participated in the Shanghai Women's Health Study, a prospective, population-based cohort study with detailed questions on environmental risk factors and family cancer history, between 1996 and 2000.
Each woman was asked whether her family members, including parents, siblings, and children, had ever been diagnosed with cancer and, if confirmed, further information was obtained on the type of cancer, and when the cancer was diagnosed.
Women with a first-degree relative with any malignancy were significantly more likely to be diagnosed with breast cancer before the age of 55 years than women without a family history of cancer (relative risk [RR]=1.41).
Risk for breast cancer was most pronounced when first-degree relatives were diagnosed with esophageal cancer (RR=2.99), bladder cancer (RR=2.60), breast cancer (RR=1.74), and lung cancer adjusted for smoking (RR=1.10).
Zhang and colleagues claim their risk estimates are likely to be conservative due to under-reporting of family history of cancer due to under-diagnosis and limited communication about cancer in families in China.
They conclude in the journal Cancer Causes and Control: "The link between breast cancer risk and family history of cancers of the lung and esophagus, as well as leukemia, warrants further investigation."
Journal
