ESMO 2021: PRIMORDIUM - A Randomized, International, Trial-in-Progress of Adding Apalutamide to Radiotherapy and an LHRH Agonist in High-Risk Patients with PSMA-PET-Positive Hormone-Sensitive Prostate Cancer

( The advent of positron emission tomography using radiolabeled prostate-specific membrane antigen (PSMA) ligands, called PSMA-PET, is rapidly changing prostate cancer staging imaging. However, as all published randomized clinical trials and studies to date have utilized conventional imaging, the impact that PSMA-PET clinical upstaging should have on treatment is unknown. To address this question, the authors present the PRIMORDIUM trial in progress (NCT04557059), which specifically evaluates the benefit of adding the androgen receptor inhibitor apalutamide to testosterone suppression and radiotherapy in patients experiencing a “high-risk” biochemical recurrence after radical prostatectomy.

Patients who experience biochemical recurrence after prostatectomy with a PSA doubling time of fewer than 12 months or had a pathologic Gleason score at surgery of 8 or higher will undergo conventional imaging as well as PSMA-PET imaging. Patients with at least 1 locoregional lesion on PSMA-PET, but negative conventional imaging, will be randomized 1:1 to radiotherapy + testosterone suppression +/- apalutamide. Radiotherapy includes whole pelvic salvage radiotherapy, with stereotactic body radiation therapy for ≤3 PSMA-avid distant metastases at sites where it is a standard approach. Systemic therapy will be administered for ~6 months. Investigators are blinded to PSMA-PET lesion locations until progression. The primary endpoint is time from randomization to PSMA-PET distant progression or death. A total of 412 patients are planned for enrollment.

Presented by: Boris A. Hadaschik, Department of Urology, University Hospital Essen, Essen, Germany

Written by: Alok Tewari, MD, PhD – Genitourinary Medical Oncologist, Instructor in Medicine, Dana-Farber Cancer Institute, Harvard Medical School, Twitter: @aloktewar during the 2021 European Society for Medical Oncology (ESMO) Annual Congress 2021, Thursday, Sep 16, 2021 – Tuesday, Sep 21, 2021.