Complete Resolution of Prostate Cancer with PSMA-Avid Retroperitoneal Lymphadenopathy After 3 Cycles of 177Lu-PSMA-617: A Case Report

Treatment of metastatic castration-resistant prostate cancer (mCRPC) with 177Lu-PSMA-617 radioligand therapy has gained traction due to its survival benefit (Sartor et al, 2021), safety, and efficacy in patients who have failed androgen receptor pathway inhibitors and taxane-based chemotherapy. While established protocols recommend six treatment cycles, this case documents complete response after three cycles in a heavily pretreated mCRPC patient.A 73-year-old male with an 11-year history of prostate adenocarcinoma (initially T2cN1M0 Gleason 9, PSA 10.1 µg/L) had been treated with external-beam radiotherapy and three years of androgen deprivation therapy. After two years without treatment, his PSA increased to 7.6 µg/L, and PSMA PET/CT confirmed PSMA-avid metastatic disease with 5–10 lymph nodes showing PSMA-expression scores of 2 and 3. He was placed on docetaxel, but his disease progressed.The patient received three cycles of 177Lu-PSMA-617 (7400 MBq per cycle) at six-week intervals. Sequential PSMA PET/CT imaging demonstrated resolution of PSMA-avid disease, with a PSMA-expression score of 1 on residual lymph nodes. PSA levels declined from 11.2 µg/L pre-treatment to 5.5 µg/L one month after the third cycle (50.9% reduction). Symptoms possibly related to treatment included fatigue, poor appetite, and bilateral lower extremity edema.This case demonstrates that complete response to 177Lu-PSMA-617 can occur after fewer than six cycles. The impact of clinical and imaging responses on treatment duration remains inadequately studied. The patient's lymph node-only metastatic pattern and PSMA-expression scores of 2 and 3 may represent predictive factors for treatment response, though further research is required.