Adjuvant Radiation Therapy Versus Initial Observation for Patients After Prostatectomy with Adverse Pathology: Have Findings from 3 Randomized Clinical Trials Influenced Clinical Practice?

Abstract

Results from three randomized clinical trials (RCTs) established initial observation with early salvage radiotherapy as the standard of care for men with adverse pathology (AP) after radical prostatectomy (RP). The aim of our study was to assess if the use of adjuvant radiotherapy (aRT) has declined since the 2020 publication of these RCTs. We retrospectively reviewed the Michigan Urological Surgery Improvement Collaborative prostate cancer registry and identified men who underwent RP from 2012 to 2024 and approximated the inclusion criteria of the RCTs: post-operative PSA ≤0.1 and AP: pT3a/pT3b/pT4 and/or positive surgical margins. The primary objective was to test for the association of time period of RP (pre-2020 vs. 2020 vs. post-2020) with the use of aRT vs. initial observation. aRT was defined as RT that was started both within 12 months of diagnosis and with PSA ≤0.1. The Kaplan-Meier method and mixed-effects multivariable Cox regression were used to evaluate an association of time period with aRT. Of 9,144 patients meeting inclusion criteria, 5,408 had RP before 2020, 764 in 2020 and 2,972 after 2020. Prior to 2020, 8.2% of patients (95% CI:7.5-9.0%) were treated with aRT, compared with 4.6% (95% CI:3.2-6.4%) in 2020 and 2.7% (CI:2.1-3.5%) after 2020. After adjustment in the multivariable model, patients undergoing RP after compared with before 2020 were less likely to receive aRT (OR 0.24, CI:0.18-0.32, p<0.001). The use of aRT decreased after 2020, consistent with level one evidence supporting initial observation in patients with AP.