Does Physical Activity Mitigate The Risk Of Frailty-related Bone Fractures Among Cancer Survivors?

Cancer and associated treatments may predispose survivors to a higher risk of frailty-related bone fractures. Whether physical activity offsets some of the excess risk is poorly understood. Prior studies lacked detailed information on physical activity (because it is not well captured by administrative data sources), had small sample sizes, and were limited to certain cancer types. PURPOSE: Investigate associations between cancer history and subsequent risk of frailty-related fractures, and to explore modification by moderate-vigorous intensity aerobic physical activity (MVPA) and weight training. METHODS: Participants from the Cancer Prevention Study-II (CPS-II) were linked to Medicare claims data for years 1999-2017. Cancer history was confirmed via medical record or cancer registry linkage starting at CPS-II enrollment (1992) and modeled as a time-dependent variable in three categories: 1) cancer survivor 1-5 years post-diagnosis (short-term), 2) cancer survivor ≥5 years post-diagnosis (longer-term), and 3) no cancer history. The first year of diagnosis was excluded to reduce the effect of treatment. Total frailty-related (pelvic, radial, vertebral) and site-specific fractures were identified in Medicare claims data using established algorithms. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for risk of fractures overall and stratified by MVPA and weight training. RESULTS: Over the course of follow-up, 14,196 frailty-related fractures were identified among 101,543 participants (including 14,159 cancer survivors). Compared to no cancer history, both short- (HR=1.28, CI: 1.18-1.38) and longer-term (HR=1.08, CI: 1.00-1.16) cancer survivors were at higher risk of total frailty-related fractures. Short-term survivors were also at higher risk of pelvic (1.34, 1.18-1.53) and radial (1.33, 1.19-1.48), but not vertebral fractures. Meeting MVPA guidelines (0.87, 0.78-0.97) and weight training (0.85, 0.74-0.99) lowered risk of fractures among longer-term survivors, but not short-term survivors (0.94, 0.81-1.09 MVPA and 0.95, 0.78-1.17 weight training). CONCLUSION: Cancer survivors are at a higher risk of frailty-related fractures, but MVPA and weight training may reduce some of the excess risk.