Identifying women at risk for advanced interval cancers would allow better targeting of mammography and supplemental screening. The authors assessed risk factors for advanced breast cancer within 2 years of a negative mammogram.
The authors included 293,520 negative mammograms performed from 2006 to 2015 among 74,736 women. Breast cancers were defined as advanced if they were >2 cm, were >1 cm and triple-negative or human epidermal growth factor receptor 2–positive, had positive lymph nodes, or were metastatic. Cox proportional hazards modeling was used to evaluate associations of age, breast density, menopause, mammogram type, prior breast biopsy, body mass index (BMI), and a family history of breast cancer with a cancer diagnosis within 2 years of a negative mammogram. Models were stratified by year since a negative mammogram.
Among 1345 breast cancers, 357 were advanced (26.5%), and 988 (73.5%) were at an early stage. Breast density, prior biopsy, and family history were associated with an increased risk of both advanced and early-stage cancers. Overweight and obese women had a 40% higher risk of early-stage cancer only in year 2 (overweight hazard ratio [HR], 1.41; 95% confidence interval [CI], 1.19-1.67; P < .001; obese HR, 1.41; 95% CI, 1.17-1.70; P < .001). Obese women had a 90% increased risk of advanced cancer in year 1 (HR, 1.90; 95% CI, 1.14-3.18; P = .014), and both overweight and obese women had a 40% or greater increased risk in year 2 (overweight HR, 1.55; 95% CI, 1.14-2.07; P = .005; obese HR, 1.42; 95% CI, 1.00-2.01; P = .051).
A higher BMI was associated with an advanced breast cancer diagnosis within 2 years of a negative mammogram. These results have important implications for risk assessment, screening intervals, and use of supplemental screening.