IntroductionSome worry that physician practices acquired by private equity may increase the use of services to maximize revenue. We assessed the effects of private equity acquisition on spending, use of treatment, and diagnostic testing in men with prostate cancer.MethodsWe used a 20% sample of national Medicare claims to perform a retrospective cohort study of men with prostate cancer diagnosed from 2014 through 2019. The primary outcome was prostate cancer spending in the first 12 months after diagnosis. Secondary outcomes included the use of treatment and a composite measure of diagnostic testing (e.g., imaging, genomics) in the first 12 months after diagnosis. Multilevel modeling was used to adjust for differences in patient and market characteristics. The effect of practice acquisition on each outcome was assessed using a difference‐in‐differences design.ResultsThere were 409 and 4021 men with prostate cancer managed by urologists in acquired and nonacquired practices, respectively. After acquisition, prostate cancer spending was comparable between acquired and nonacquired practices (difference‐in‐differences estimate $1182, p = 0.36). Acquisition did not affect the use of treatment (difference‐in‐differences estimate 3.7%, p = 0.30) or the use of diagnostic testing in men who were treated (difference‐in‐differences −5.5%, p = 0.12) and those managed conservatively (difference‐in‐differences −2.0%, p = 0.82).ConclusionsIn the year following acquisition of urology practices, private equity did not increase prostate cancer spending, the use of treatment or diagnostic testing in men with prostate cancer. Future work should evaluate the effects of private equity acquisition on practice patterns and quality over a longer time horizon.