Spillover Effects of Medicare Advantage on Traditional Medicare Beneficiaries With Prostate Cancer

Medicare Advantage (MA) managed care plans, now chosen by 51% of Medicare beneficiaries, are incentivized to constrain healthcare spending and utilization, a shift in financial incentives compared to Traditional Medicare's fee-for-service payment model. Beyond its primary beneficiaries, MA's mechanisms to constrain utilization may impact Traditional Medicare beneficiaries with prostate cancer through "spillover" effects on physician behavior.

From a 20% sample of Medicare claims, we identified patients diagnosed with prostate cancer from 2016 to 2019. We calculated MA penetration [MA beneficiaries/(Traditional Medicare and MA beneficiaries)] at the practice-level. We assessed the relationship between practice-level MA penetration and two measures of quality-potential overtreatment (i.e., treatment among those with > 75% noncancer mortality within 10 years of diagnosis) and confirmatory testing (repeat prostate biopsy, MRI, or genomic test)-using a multilevel logistic regression. We also assessed two measures of utilization, price standardized spending (i.e., global utilization) and overall treatment.

We identified 41,092 patients. Median practice-level MA penetration was 33% (IQR 23%-43%). Increasing practice-level MA penetration was associated with increased odds of overall treatment among all Traditional Medicare beneficiaries (adjusted OR 1.03 (95% CI 1.01-1.05), p = 0.01, per 10% increase in MA penetration). However, MA penetration was not associated with our quality measures, potential overtreatment and confirmatory testing, or price-standardized spending.

MA penetration at the urology practice-level varies considerably. In men with prostate cancer, greater practice-level MA penetration was associated with increased odds of treatment, but not overall utilization-even where it might influence quality.