Performance of the Breast Cancer Risk Assessment Tool Among Women Aged 75 Years and Older

Background: The Breast Cancer Risk Assessment Tool (BCRAT, “Gail model”) is commonly used for breast cancer prediction; however, it has not been validated for women age 75 years and older. Methods: We used Nurses’ Health Study (NHS) data beginning in 2004 and Women’s Health Initiative (WHI) data beginning in 2005 to compare BCRAT’s performance among women age 75 years and older with that in women age 55 to 74 years in predicting five-year breast cancer incidence. BCRAT risk factors include: age, race/ethnicity, age at menarche, age at first birth, family history, history of benign breast biopsy, and atypia. We examined BCRAT’s calibration by age by comparing expected/observed (E/O) ratios of breast cancer incidence. We examined discrimination by computing c-statistics for the model by age. All statistical tests were two-sided. Results: Seventy-three thousand seventy-two NHS and 97 081 WHI women participated. NHS participants were more likely to be non-Hispanic white (96.2% vs 84.7% in WHI, P < .001) and were less likely to develop breast cancer (1.8% vs 2.0%, P = .02). E/O ratios by age in NHS were 1.16 (95% confidence interval [CI] = 1.09 to 1.23, age 57–74 years) and 1.31 (95% CI = 1.18 to 1.45, age ≥ 75 years, P = .02), and in WHI 1.03 (95% CI = 0.97 to 1.09, age 55–74 years) and 1.10 (95% CI = 1.00 to 1.21, age ≥ 75 years, P = .21). E/O ratio 95% confidence intervals crossed one among women age 75 years and older when samples were limited to women who underwent mammography and were without significant illness. C-statistics ranged between 0.56 and 0.58 in both cohorts regardless of age. Conclusions: BCRAT accurately predicted breast cancer for women age 75 years and older who underwent mammography and were without significant illness but had modest discrimination. Models that consider individual competing risks of non–breast cancer death may improve breast cancer risk prediction for older women. Women age 75 years and older are the fastest growing segment of the US population, and breast cancer incidence increases with age (1). However, none of the randomized trials evaluating mammography screening included women age 75 years and older. Therefore, it is not known if screening helps these women live longer (2). Ideally, screening decisions would consider an M. A. Schonberg et al. | 2 of 11 a r t ic le a r t ic le older woman’s breast cancer risk, life expectancy, and preferences (3,4). While there are tools to help estimate life expectancy (5) and elicit patient preferences (6), little is known about late-life breast cancer risk factors. The Breast Cancer Risk Assessment Tool (BCRAT) is the most commonly used breast cancer risk prediction model in primary care; however, its performance among women age 75 years and older is not known (7–9). BCRAT was developed from a statistical model known as the Gail model, which was developed using data from the Breast Cancer Detection Demonstration Project (BCDDP), a study that recruited 280 000 women age 35 to 74 between 1973 and 1980 (10,11). BCRAT considers a woman’s age, race/ethnicity, age at menarche, age at first live birth, number of first-degree relatives with breast cancer, number of benign breast biopsies, and history of atypical hyperplasia. However, several of these risk factors (eg, age at menarche) affect women’s estrogen levels relatively early in life and may not be important for latelife breast cancer risk (4). Therefore, we aimed to assess BCRAT’s performance among women age 75 years and older compared with that in postmenopausal women age 55 to 74 years participating in the Nurses’ Health Study (NHS) and Women’s Health Initiative (WHI). We chose these cohorts because they include many women age 75 years and older and have captured necessary data on breast cancer risk factors. Our goal was to determine BCRAT’s accuracy for assessing breast cancer risk when deciding whether or not to screen women age 75 years and older for breast cancer.