A new study has reported that a lifestyle incorporating three behaviors designed to reduce risk of breast cancer can in fact reduce this risk among postmenopausal women whether or not they have a family history of later-onset breast cancer. Later-onset was defined for purposes of the study as occurring at age 45 or older. Women with close relatives with breast cancer before age 45 were excluded since they might have a more dominant genetic risk of breast cancer. A family history of later-onset breast cancer may be the result of multiple factors contributing to inheritance of breast cancer risk, including unfavorable lifestyle patterns. In the study, the authors assessed whether maintaining a healthful body weight, being physically active and limiting alcohol intake influences risk of breast cancer. The study included 85,644 initially cancer-free postmenopausal women enrolled into the Women's Health Initiative Observational Study between 1993 and 1998. Breast cancer outcomes through August 2003 were analyzed in relationship to lifestyle and risk factors collected by questionnaire at enrollment. A total of 1,997 participants were diagnosed with invasive breast cancer during a follow-up period averaging 5.4 years.

The incidence of invasive breast cancer among women with a family history of later-onset breast cancer who fully participated in all three behaviors (maintaining normal body weight, exercising vigorously for at least 20 minutes five or more days per week, drinking no more than one alcoholic beverage per day) was found to be 5.94 per 1,000 woman-years, compared to 6.97 among women who were overweight, did not exercise much or at all, and drank more than one alcoholic beverage per day. In comparison, the incidence among women with no family history of later-onset breast cancer who fully participated in all three favorable behaviors was 3.51 per 1,000 woman-years compared to 4.67 for those who participated in none. The authors conclude that participating in the three breast-healthy behaviors was beneficial to postmenopausal women. The relative amount of risk reduced by adhering to the three healthy behaviors was the same for women with and without a family history of later-onset breast cancer.