PSMA-PET/CT-Guided Intensification of Radiation Therapy for Prostate Cancer (PSMAgRT): Findings of Detection Rate, Effect on Cancer Management, and Early Toxicity From a Phase 2 Randomized Controlled Trial

Abstract

Prostate-specific membrane antigen (PSMA) ligand positron emission tomography (PET) is increasingly integrated in prostate cancer management because of its diagnostic performance. We sought to evaluate the effect of PSMA-PET/computed tomography (CT)-guided intensification of radiation therapy (PSMAgRT) on patient outcomes. Here, we report secondary trial endpoints including the rate of new lesion detection, effect on prostate cancer management, and treatment-related toxicities. In this phase 2 cohort multiple randomized controlled trial across 2 institutions, men with prostate cancer planned for RT were randomly selected for PSMAgRT across 4 strata: oligometastatic, high risk (Cancer of the Prostate Risk Assessment ≥6 or cN1), salvage post-RT, and salvage postprostatectomy (RP). Primary endpoint was failure-free survival at 5 years, with analysis pending further follow-up. Secondary endpoints included new lesion detection yield of PSMA-PET/CT, acute and delayed toxicities, effect on prostate cancer management, and health-related quality-of-life outcomes. This trial is registered with ClinicalTrials.gov, identifier NCT03525288, companion to registry NCT03378856. Between May 2018 and February 2021, 262 patients were enrolled and randomized. Nine patients were later excluded (5 control, 4 PSMAgRT), leaving 253 patients for analysis (23 oligometastatic, 86 high risk, 16 salvage post-RT, and 128 salvage post-RP). New lesions were detected in 45.5% of oligometastatic, 39.5% of high risk, 14.3% of salvage post-RT, and 51.6% of salvage post-RP. Overall, PSMA-PET/CT led to intensification of RT in over half of patients (52.0%), with minimal intensification of systemic therapy (4.0%). With a median follow-up of 12.9 months, this intensification was associated with 3 attributable grade 3+ events (2.5% of patients undergoing PSMAgRT) but no difference in the rate of grade 2+ events attributable to RT compared with controls (43%, both arms). In this randomized trial, PSMA-PET/CT led to intensification of RT in more than half of patients. Longer follow-up is required to determine whether this intensification translates to effect on cancer control and long-term toxicity and health-related quality-of-life outcomes.