68Ga-PSMA Ligand PET/CT-based Radiotherapy for Lymph Node Relapse of Prostate Cancer After Primary Therapy Delays Initiation of Systemic Therapy.

AIM To evaluate 68Ga-PSMA ligand positron-emission tomography-computed tomography (PET/CT)-based radiotherapy for lymph node metastases of prostate cancer after primary therapy. PATIENTS AND METHODS Twenty-three patients received radiotherapy for PSMA ligand-positive lymph node metastases. RESULTS The median follow-up time was 12.4 (range=6.0-28.5) months. The median pre-treatment prostate-specific antigen (PSA) decreased from 2.75 (range=0.52-8.92) ng/ml to a nadir of 1.37 (range=0.11-8.00) ng/ml (p=0.001) following radiotherapy. Except for one patient (4.4%), PSA level decreased in 22 patients (95.6%). The biochemical failure-free survival and time to initiation of systemic therapy at the median follow-up were 95.6% and 100%, respectively. Three patients (12.9%) presented with recurrent disease outside the initial radiation field. No grade III acute toxicities or late grade II toxicities were observed. CONCLUSION 68Ga-PSMA ligand PET/CT-based radiotherapy is a promising local treatment option for isolated lymph node metastases of prostate cancer.