Breast Cancer Risk From Modifiable and Nonmodifiable Risk Factors Among White Women in the United States

Authors: Maas, P. et. al.

Source: JAMA Oncol. doi:10.001/jamaoncol.2016.1025

oncology.jamanetwork.com/article.aspx?articleid=2524829

Certain factors are known to increase breast cancer risk. These include body weight, menopause hormone replacement therapy, ages at first menses and last menstrual period and alcohol consumption. More recently, studies have revealed genetic features called single nucleotide polymorphisms (SNPs) that increase breast cancer risk. To date, 92 breast cancer-related SNPs have been found. Most agree that, separately, each of these factors and each SNP have minimal effect on breast cancer risk. However, when combined, their effects may be substantial.

The investigators created a polygenic risk score (PRS) based on the presence of the 92 SNPs. This was combined with a woman’s family history, childbirth history, ages at first and last menses, height and weight. Combined, these were considered nonmodifiable risk factors. Additionally, the group looked at each woman’s body mass index (BMI – the ratio of body weight to height), menopausal hormone replacement use, level of alcohol consumption and smoking status. Combined, these were considered modifiable risk factors. Subjects were from 8 databases in Europe, Australia and the US that follow women along for the development of breast cancer. For this study, breast cancer developed in 17,171 women; 19,862 were cancer-free.  Each woman’s genetic profile and personal history were assessed, creating a breast cancer risk for each.

This model of nonmodifiable and modifiable factors produced a reliable assessment of breast cancer risk. The modifiable factors, however, did not affect risk equally for each subject. Women who were increased risk due to nonmodifiable factors had that risk reduced significantly by changing modifiable risk factors. For women who had low breast cancer risk based on nonmodifiable factors, changing their modifiable factors had much less benefit for their breast cancer risk.

This study concludes that weight loss, smoking cessation and abstinence from alcohol may be very effective for some women, but have no effect on breast cancer risk for others. Information such as this may help providers make individualized and more accurate recommendations about risk-reducing medications and lifestyles and breast cancer screening in the future.