Ga-PSMA PET/CT for Patients with Prostate Cancer with PSA Relapse

In Danish guidelines for imaging of patients with prostate cancer and PSA relapse, PSMA PET/CT is the recommended restaging modality. A multicenter study has been initiated to analyze findings of 68Ga-PSMA PET/CT scans for patients with prostate cancer with PSA relapse. This report details preliminary findings of 779 patients in six cohorts from three continents. At the time of the restaging, the PSA values were grossly similar between the six cohorts, with an important subgroup of the patients having PSA values lt; 1 ng/ml. Patients who initially underwent radical prostatectomy had lower PSA values at the restaging than patients who were initially treated with external beam radiation therapy or brachytherapy. Even for patients with restaging PSA values lt; 0.5 ng/ml, some patients had positive sites in extra pelvic lymph nodes and bones. Patients were followed up to 7 years after the restaging PSMA PET/CT. In multiple Cox regression analysis of 196 patients, only the number of positive sites on 68Ga-PSMA PET/CT significantly predicted overall survival (p = 0.0001). The findings illustrate why restaging PSMA PET/CT change salvage treatment for up to half of the patients with PSA relapse compared with planned salvage treatment based on only conventional imaging modalities like CT and bone scans.