Unusual Metastatic Prostate Cancer in Subcarinal Lymph Node and Peritoneal Nodule Found on ¹⁸F-PSMA PET/CT With Rising PSA of 0.4 ng/mL

A 79-year-old man with metastatic prostate cancer underwent radical prostatectomy and bilateral lymph node dissection and received multiple lines of systematic treatment for his biopsy-proven peritoneal carcinomatosis. During the disease course, his prostate-specific antigen rose from 0.1 ng/mL to 0.4 ng/mL in 4 months, and testosterone level was <3 ng/dL. Workup 18F-DCFPyL PET/CT showed unusual prostate-specific membrane antigen-avid, 1.1-cm subcarinal lymph node and a 0.8-cm peritoneal nodule, which were not hypermetabolic on an 18F-FDG PET/CT 6 days later. This case illustrated the sensitivity for 18F-DCFPyL PET/CT in detecting metastatic castration-resistant prostate cancer.