MODELING BREAST CANCER RISK IN YOUNGER WOMEN – A FIRST STEP IN THE DEVELOPMENT OF RISK-STRATIFIED MAMMOGRAPHIC SCREENING
The US Preventive Services Task Force recommends biennial breast cancer screening for women ages 50 to 74 with average risk of breast malignancy. Consensus exists regarding annual mammographic screening of selected high risk individuals. However there is uncertainty about screening women under age 50 with intermediate breast cancer risk. This study modeled lifetime breast cancer risk in the US population of women ages 35 to 49 to facilitate future development of risk-stratified screening.
Data from the US Census Bureau, National Cancer Institutes, Breast Cancer Screening Consortium, and the National Health Interview Survey were used to estimate breast cancer risk factor prevalence in the US population. Family history, parity, previous breast biopsy, breast density, and BRCA1&2 mutations were considered as informative risk factors. Monte Carlo simulation modeling was used to estimate proportions of the population with low to average (≤12.5%), intermediate (12.6%-30%), and high (>30%) lifetime breast cancer risk.
Women ages 35 to 49 make up 10% of the US population and 27% of all adult women. Estimates of risk factor prevalence demonstrated that 6% (95%CI: 5.8-7.1%) have at least one first degree relative with breast cancer, 24%(95%CI: 22.5-24.7%) are nulliparous, 2% (95%CI: 1.9-2.7) had a previous breast biopsy, 55% (95%CI: 54-55%) have BIRADS III or IV breast density, and 0.9% (95%CI: 0.5-1.2%) carried BRCA1 or 2 mutations. Based on this risk factor prevalence, an estimated 87% of women have low to average risk, 12% have intermediate risk, and 1% have a high lifetime risk of breast cancer.
A substantial proportion of women ages 35 to 49 in the US are estimated to have intermediate lifetime risk of breast cancer. Therefore further development of risk-stratified screening in this age group is warranted.