Development and Validation of a Simulation Model–Based Tool to Support Individualized Physical Activity Discussions and Prescriptions for Breast Cancer Survivors

PURPOSE: Clinical guidelines recommend offering individualized physical activity prescriptions to cancer survivors. However, there are limited tools to support individualized physical activity discussions and prescriptions. We developed and validated a simulation model-based tool to estimate individualized survival outcomes for postdiagnosis physical activity among postmenopausal breast cancer survivors. METHODS: We adapted an established simulation modeling approach developed within the Cancer Intervention and Surveillance Modeling Network to estimate breast cancer-specific and all-cause survival associated with postdiagnosis physical activity for 50- to 75-year-old (postmenopausal) women with stage I to III invasive breast cancer. Model estimates were generated for 60,480 subgroups based on age, weight status (BMI), stage, tumor subtype, treatment, aerobic (<30 min/wk [no/minimal], ≥30 to <150 min/wk [insufficient], ≥150 to <300 min/wk [active], ≥300 min/wk [highly active]), and muscle-strengthening (<2 or ≥2 d/wk) activity. The outcomes were 10-year survival and absolute survival benefits for different levels of physical activity by individual characteristics and treatment. Model inputs were derived from trials, cohort studies, registry, and surveillance data. External validation used independent data. RESULTS: Survival rates and absolute benefits for physical activity varied by age, weight status, stage, tumor subtype, and amount and type of activity. For example, the 10-year breast cancer-specific and all-cause survival for no/minimal activity in a 65- to 69-year-old-woman with stage II, hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer with obesity was 79.2% and 72.2%, respectively. Increasing aerobic activity from no/minimal to insufficient activity with <2 d/wk of muscle-strengthening was associated with absolute increases in 10-year breast cancer-specific and all-cause survival by 2.8 and 3.4 percentage points, respectively. The model closely replicated survival rates in independent data. CONCLUSION: Simulation model-based estimates could support clinical tools for guideline-recommended individualized discussions and physical activity prescriptions for breast cancer survivors.