Validation of a Dynamic Risk Prediction Model Incorporating Prior Mammograms in a Diverse Population

Abstract

Importance: For breast cancer risk prediction to be clinically useful, it must be accurate and applicable to diverse groups of women across multiple settings.

Objective: To examine whether a dynamic risk prediction model incorporating prior mammograms, previously validated in Black and White women, could predict future risk of breast cancer across a racially and ethnically diverse population in a population-based screening program.

Design, setting, and participants: This prognostic study included women aged 40 to 74 years with 1 or more screening mammograms drawn from the British Columbia Breast Screening Program from January 1, 2013, to December 31, 2019, with follow-up via linkage to the British Columbia Cancer Registry through June 2023. This provincial, organized screening program offers screening mammography with full field digital mammography (FFDM) every 2 years. Data were analyzed from May to August 2024.

Exposure: FFDM-based, artificial intelligence-generated mammogram risk score (MRS), including up to 4 years of prior mammograms.

Main outcomes and measures: The primary outcomes were 5-year risk of breast cancer (measured with the area under the receiver operating characteristic curve [AUROC]) and absolute risk of breast cancer calibrated to the US Surveillance, Epidemiology, and End Results incidence rates.

Results: Among 206 929 women (mean [SD] age, 56.1 [9.7] years; of 118 093 with data on race, there were 34 266 East Asian; 1946 Indigenous; 6116 South Asian; and 66 742 White women), there were 4168 pathology-confirmed incident breast cancers diagnosed through June 2023. Mean (SD) follow-up time was 5.3 (3.0) years. Using up to 4 years of prior mammogram images in addition to the most current mammogram, a 5-year AUROC of 0.78 (95% CI, 0.77-0.80) was obtained based on analysis of images alone. Performance was consistent across subgroups defined by race and ethnicity in East Asian (AUROC, 0.77; 95% CI, 0.75-0.79), Indigenous (AUROC, 0.77; 95% CI 0.71-0.83), and South Asian (AUROC, 0.75; 95% CI 0.71-0.79) women. Stratification by age gave a 5-year AUROC of 0.76 (95% CI, 0.74-0.78) for women aged 50 years or younger and 0.80 (95% CI, 0.78-0.82) for women older than 50 years. There were 18 839 participants (9.0%) with a 5-year risk greater than 3%, and the positive predictive value was 4.9% with an incidence of 11.8 per 1000 person-years.

Conclusions and relevance: A dynamic MRS generated from both current and prior mammograms showed robust performance across diverse racial and ethnic populations in a province-wide screening program starting from age 40 years, reflecting improved accuracy for racially and ethnically diverse populations.

Figure 1.. Dynamic Risk Prediction Using Prior Mammograms With Current Visit to Predict a 5-Year Future Risk of Breast Cancer

The model is compatible with women with a current mammogram only (red) as well as those with prior history of mammograms accompanied with various visit intervals (green and blue). Orange dots denote index mammogram, and brown dots denote prior mammograms. The red X indicates breast cancer.

Figure 2.. Distribution of Incidence Per 1000 Person-Years by National Comprehensive Cancer Network (NCCN), American Society of Clinical Oncology (ASCO), and US Preventive Services Task Force (USPSTF) Risk Cut Points Applied to 5-Year Risk in British Columbia

Orange bars denote incidence after excluding cases diagnosed within 6 months of entry to cohort.

Figure 3.. Calibration Plot of Observed vs Predicted 5-Year Breast Cancer Risk With Observed 95% CI in the British Columbia Breast Screening Program by Decile of Predicted Risk