Small Lymph Node Metastasis Detected by 68Ga-Prostate-Specific Membrane Antigen But Not 18F-Fluciclovine PET/CT in Low-Prostate-Specific Antigen Biochemical Recurrence of Prostate Cancer.

A 58-year-old man with Gleason 4+3 prostate cancer was initially treated by radical prostatectomy followed by salvage radiotherapy to the prostate bed for postoperative biochemical failure. One year later, F-fluorocholine PET/CT detected a pelvic lymph node recurrence, which was treated with radiation therapy and 6 months of androgen deprivation. PSA started to rise again 18 months later, but F-fluciclovine PET/CT failed to demonstrate the site of recurrence at a PSA of 0.63 ng/mL. However, Ga-PSMA PET/CT revealed a single positive 4-mm perirectal lymph node (PSA 0.80 ng/mL at time of scan), in retrospect anatomically apparent but negative on F-fluciclovine PET/CT.