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New Model Estimates Impact of Breast-Cancer Risk Factors

Model assesses impact of changes in modifiable risk factors on absolute breast cancer risk

TUESDAY, June 28 (HealthDay News) -- A new breast cancer risk model predicts that changes in the modifiable risk factors in a woman's lifestyle may reduce the absolute risk of developing breast cancer, according to a study published online June 24 in the Journal of the National Cancer Institute.

Elisabetta Petracci, Ph.D., from the National Cancer Institute in Bethesda, Md., and colleagues investigated the impact of changes in modifiable risk factors on the absolute risk of breast cancer. The investigators developed a model using data from 2,569 breast cancer patients and 2,588 controls who participated in an Italian study from 1991 to 1994, and incidence and mortality data from Florence Registries. The model included five non-modifiable risk factors (reproductive characteristics, education, occupation, and family and biopsy history) and three modifiable risk factors (alcohol consumption, physical activity, and body mass index). The model was validated using independent data from another study. High-risk subgroups were identified for calculation of the percent risk reduction.

The investigators found that their model was reasonably well calibrated (ratio of expected to observed cancers, 1.10) with modest discriminatory accuracy. The absolute risk reduction from exposure modifications increased with age and risk projection time span, and was nearly proportional to the risk before modifying the risk factors. For women aged 65 years, the mean 20-year reduction in absolute risk was 1.6 percent in the entire population, 3.2 percent in women with a family history of breast cancer and 4.1 percent in women in the high risk group.

"These data give perspective on the potential reductions in absolute breast cancer risk from preventative strategies based on lifestyle changes," the authors write.

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