The development and validation of a simulation model–based calculation engine to support individualized physical activity prescriptions for breast cancer survivors.

10517 Background: Current cancer physical activity guidelines recommend clinicians offer individualized ‘physical activity prescriptions’ to cancer survivors. However, there are limited data to support individualized physical activity prescriptions for breast cancer survivors in clinical settings. We aimed to develop a simulation model-based ‘calculation engine’ for a clinical decision tool that could generate individualized breast cancer outcomes associated with physical activity considering the individual characteristics of breast cancer survivors. Methods: We adapted an established and validated simulation model developed within the Cancer Intervention and Surveillance Modeling Network (CISNET) to estimate breast cancer-specific mortality, all-cause mortality, and life-years gained with post-treatment physical activity for women aged 50-75 years at diagnosis with stage I-III breast cancer. Model inputs were derived from clinical trials, cohort studies, national survey, and registry data. Breast outcomes were generated for 41,472 unique subgroups based on all possible combinations of age, hormone status, HER2 status, stage, tumor size, grade, body mass index, surgery, and treatment. External validation was conducted using an independent data source. We summarized 10-year breast cancer and all-cause mortality rates for varying combinations of weekly aerobic (e.g., 2.5-5.0 hours/week) and muscle-strengthening (e.g., ≥2 days/week) activity. Results: Overall, the 10-year breast cancer-specific and all-cause survival rates for stages I-III were 89.1% and 83.2%. These results varied by individual characteristics and physical activity levels. For example, in a 65-69-year-old-woman diagnosed with stage I, hormone receptor-positive, HER2-negative breast cancer, and a body mass index of ≥30kg/m2, the 10-year breast cancer-specific and all-cause survival rates for 0-0.5 hours/week of physical activity were 87.1% and 80.1%, respectively. If the woman was to increase aerobic activity to 0.5-2.5 hours/week, 10-year breast cancer survival increased to 88.5%, and all-cause survival increased to 81.1%. Meeting physical activity guidelines (i.e., 2.5-5.0 hours/week of moderate-intensity aerobic activity; and ≥2-days/week of muscle strengthening activity) was associated with increases in 10-year breast cancer and all-cause survival rates to 93.0% and 82.9%, respectively. The model closely replicated observed rates in independent data. Conclusions: These data provide a calculation engine for a clinical decision tool to support individualized physical activity prescriptions and discussions for breast cancer survivors.