Abstract
BACKGROUND: Urologists practicing in single-specialty groups with ownership in radiation vaults are more likely to treat men with prostate cancer. The effect of divestment of vault ownership on treatment patterns is unclear. METHODS: A 20% sample of national Medicare claims was used to perform a retrospective cohort study of men with prostate cancer diagnosed between 2010 and 2019. Urology practices were categorized by radiation vault ownership as nonowners, continuous owners, and divested owners. The primary outcome was use of local treatment, and the secondary outcome was use of intensity-modulated radiation therapy (IMRT). A difference-in-differences framework was used to measure the effect of divestment on outcomes compared to continuous owners. Subgroup analyses assessed outcomes by noncancer mortality risk (high [>50%] vs. low [≤50%]). RESULTS: Among 72 urology practices that owned radiation vaults, six divested during the study. Divestment led to a decrease in treatment compared with those managed at continuously owning practices (difference-in-differences estimate, -13%; p = .03). The use of IMRT decreased, but this was not statistically significant (difference-in-differences estimate, -10%; p = .13). In men with a high noncancer mortality risk, treatment (difference-in-differences estimate, -28%; p < .001) and use of IMRT (difference-in-differences estimate, -27%; p < .001) decreased after divestment. CONCLUSIONS: Urology group divestment from radiation vault ownership led to a decrease in prostate cancer treatment. This decrease was most pronounced in men who had a high noncancer mortality risk. This has important implications for health care reform by suggesting that payment programs that encourage constraints on utilization, when appropriate, may be effective in reducing overtreatment.