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

## TL;DR

This study examines how Medicare Advantage plans may influence treatment decisions for prostate cancer patients in Traditional Medicare, finding increased treatment odds but no impact on quality or spending.

## Contribution

The study reveals spillover effects of Medicare Advantage on Traditional Medicare beneficiaries with prostate cancer, showing increased treatment odds without affecting quality metrics.

## Key findings

- Higher Medicare Advantage penetration was associated with increased odds of overall treatment among Traditional Medicare beneficiaries.
- No significant association was found between Medicare Advantage penetration and quality measures like potential overtreatment or confirmatory testing.
- Increased treatment odds were observed without changes in price-standardized spending or quality outcomes.

## Abstract

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.

MA penetration at the urology practice‐level varies considerably. Higher MA penetration was associated with increased treatment, namely surgery, among patients with Traditional Medicare without changes in quality. Our work suggests that, in the context of prostate cancer, increasing MA penetration may not always be associated with constrained utilization among Traditional Medicare beneficiaries.