A model using 92 common susceptibility single nucleotide polymorphisms (SNPs) predicted that, for women at a higher risk for breast cancer, secondary to non-modifiable and genetic risk factors may be mitigated by healthful lifestyle choices.1
“Women who may be at high risk due to genetics, family history, or other non-modifiable risk factors may feel discouraged that, because of ‘bad luck’, their risk is high and they cannot do much about it,” said Nilanjan Chatterjee, PhD, of the Department of Biostatistics at Bloomberg School of Public Health at Johns Hopkins University in Baltimore, Maryland, in an interview with Cancer Therapy Advisor.
“We are hopeful that women who are at high risk due to ‘bad-luck’ are the ones who will benefit most by modifying their lifestyles. But a healthful lifestyle has benefits for everybody and that message should not be lost either,” Dr Chatterjee continued.
Using data from the Breast and Prostate Cancer Cohort Consortium (BPC3) combined with epidemiologic risk factors and SNPs, Dr Chatterjee and colleagues developed a model for predicting the absolute risk of invasive breast cancer. The model was used to estimate the effect that risk-factor modification could have on breast cancer prevention in white American women, at differing levels of non-modifiable risk.
Data were analyzed from 17,171 cases of breast cancer and 19,862 controls obtained from 8 prospective cohort studies.
The absolute, cumulative 50-year risk of invasive breast cancer development for a 30 year old white female in the United States was calculated to be an average of 11.3%. When all provided risk factors were included, the average risk ranged from 4.4% at the bottom decile of risk distribution to 23.5% at the top decile of risk distribution.
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For women in the lowest decile of non-modifiable risk, the risk distribution tied to identified, modifiable risk factors (such as BMI, menopausal hormone therapy, alcohol use, and smoking) ranged from 2.9% to 5.0%. Women in the highest decile of non-modifiable risk demonstrated a risk distribution for modifiable risk factors of 15.5% to 25.0%. The investigators found that the women at the lowest risk from modifiable risk factors were women who did not smoke, did not drink alcohol, did not use menopausal hormones, and had a lower BMI.
They suggested that if all white American women were at the lowest risk for the 4 modifiable risk factors, an estimated 28.9% of breast cancers could be prevented. Women with the highest non-modifiable risk were no more at risk than the general population if they did not smoke, drink alcohol, use menopausal hormone therapy, and had a low BMI.
One limitation of the study was a lack of data evaluating other known breast cancer risk factors, such as physical activity, breastfeeding, education, and breast density.
Dr Chatterjee noted that because the common genetic markers used in the study are not proactively tested, the results of this study may not affect patient counseling. “The results could be used for positive messaging in general. The fact that some women benefit from a healthful lifestyle even more than what has been known before, could encourage women in general to adopt healthful lifestyle,” he concluded.
1. Maas P, Barrdahl M, Joshi AD, Auer PL, Gaudet MM, Milne RL, et al. Breast cancer risk from modifiable and nonmodifiable risk factors among white women in the United States [published online ahead of print May 26, 2016]. JAMA Oncol. doi: 10.1001/jamaoncol.2016.1025.