Has PSMA-PET Adoption for Prostate Cancer Staging Impacted Population-Level Treatment Allocation? A Difference-in-Differences Analysis of a Statewide Quality Collaborative

Document Type

Conference Proceeding

Publication Date

6-9-2025

Abstract

Research Objective: While prostate specific membrane antigen-positron emission tomography (PSMA-PET) for staging of unfavorable intermediate (UIR) and high risk (HR) prostate cancer (PCa) is guideline-supported based on diagnostic accuracy, this new technology’s real-world impact on patient care is unknown. Compared to conventional imaging, PSMA-PET is more sensitive in detecting previously occult disseminated disease. However, whether this increased detection in the staging setting materially changes patient management is unknown and significant in light of PSMA-PET’s access and cost issues. We hypothesize that PSMA-PET adoption is associated with decreased rates of radical prostatectomy, given that patients with more advanced disease preferentially undergo radiation and androgen deprivation therapy.

Study Design: This was an observational study using difference-in-differences mixed effects logistic regression with receipt of radical prostatectomy as the dependent variable. We compared receipt of prostatectomy before (prior to 1/1/2020) and after (subsequent to 6/30/2022) PSMA-PET adoption. The intervening washout period (1/2020 through 6/2022) controlled for COVID and time from FDA approval (12/2020) to initial PSMA-PET data collection within Michigan (7/1/2022). Patients with UIR are far less likely to harbor occult nodal or micrometastatic disease or undergo PSMA-PET imaging, therefore serving as the “unexposed” group, relative to PSMA-PET “exposed” HR patients. An interaction term between period (pre- vs. post-adoption) and risk grouping (UIR vs. HR) estimated the impact of PSMA-PET on receipt of radical prostatectomy after adjusting for patient characteristics and practice- and surgeon-level clustering via nested random effects.

Population Studied: 21,208 patients with newly diagnosed with UIR and HR PCa were identified in the Michigan Urological Surgery Improvement Collaborative (MUSIC) data registry between 2018 and 2024. After excluding patients diagnosed during the washout period, 13,049 patients comprised the cohort.

Principal Findings: 7,559 patients were diagnosed prior to adoption, compared with 5,490 post-adoption period. Patients were significantly younger (median 68 vs. 69 years old, p< 0.001) and more likely to be Caucasian (82% vs 80%, p=0.022) in the pre-adoption period, while the proportion of patients with HR disease was similar across both periods (58% vs 59%, p=0.3).

The Table reports a multivariable model predicting receipt of radical prostatectomy. An interaction term for time period (pre- vs. post-) and risk grouping was not statistically significant (p=0.4). Caucasian race, younger age, and UIR disease were associated with increased odds of surgery.

Conclusions: Adoption of staging PSMA-PET was not associated with a significant population-level impact on PCa treatment. Our findings highlight the substantial complexity of clinical decision-making, particularly when incorporating both novel and conventional risk factors.

Implications for Policy or Practice: Real-world impact of novel technologies should not be taken for granted. Trials evaluating the clinical impact of new diagnostic and prognostic tests should be emphasized.

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AcademyHealth Annural Research Meeting, June 7-10, 2025, Minneapolis, MN

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