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Almost one-third of breast cancer cases traced to modifiable behavior

Recent study data published in JAMA Oncology suggest that 29% of breast cancer cases among white women in the United States could be prevented if women avoided smoking and drinking, did not use any menopausal hormones and maintained a lean body mass.

“People think that their genetic risk for developing cancer is set in stone,” Nilanjan Chatterjee, PhD, of the department of biostatistics at Johns Hopkins University Bloomberg School of Public Health, said in a press release. “While you can’t change your genes, this study tells us even people who are at high genetic risk can change their health outlook by making better lifestyle choices such as eating right, exercising and quitting smoking.”

For women living in Western developed countries, breast cancer is the most common form of cancer, the researchers wrote. Epidemiologic data has identified factors that can increase the risk for breast cancer, including smoking, hormone use, anthropometry, alcohol consumption and reproductive history. Recently, genome-wide association studies have found 92 common loci marked by single nucleotide polymorphisms (SNPs) that are also associated with breast cancer risk. Using the 92 SNPs and epidemiologic risk factors, Chatterjee and colleagues developed a model that identifies the absolute risk for breast cancer, taking into account both modifiable risk factors and nonmodifiable risk factors.

To develop their model, the researchers assessed 17,171 cases and 19,862 controls sampled from the Breast and Prostate Cancer Cohort Consortium, and 5,879 women who participated in the 2010 National Health Interview Survey.

The researchers found that the absolute risk for a white woman aged 30 years living in the United States to develop breast cancer by age 80 is 11.3%. The model showed that women with the lowest decile of risk distribution face a 4.4% risk (95% CI, 2.9-5), while women in the highest decile have a 23.5% risk (95% CI, 15.5-25). For women in the highest decile due to nonmodifiable factors, those who had low BMI, did not smoke or drink, and did not use menopausal hormone therapy had risks comparable to an average woman in the population, suggesting that individuals can substantially lower their risk by changing their behaviors.

Modifying most known factors could prevent approximately 29% of breast cancer cases, the researchers wrote.

“Everyone should be doing the right things to stay healthy but motivating people is often hard,” Chatterjee said. “These findings may be able to help people better understand the benefits of a healthy lifestyle at a more individualized level.”

In a related editorial also published in JAMA Oncology, William D. Dupont, PhD, in the department of biostatistics at Vanderbilt University School of Medicine, and colleagues recommended that the model should not be used to counsel individual patients because it cannot be calibrated.

“While we believe that the overarching goal of the authors and research community is laudable, it remains premature to use this model to support such clinical decision making,” they wrote. “To their credit, Maas et al. do state that, ‘randomized trials will be needed to understand the true impact of an intervention.’ We concur.” – by Will Offit

Disclosures: The researchers report no relevant financial disclosures.