Oligometastatic Lymph Node Recurrence Detected Using 18F-PSMA-1007 PET/CT in a Patient With Castration-resistant Prostate Cancer After Radiation Therapy

Background/Aim: Prostate cancer (PC) is one of the most common types of cancer in men worldwide. Most patients with metastatic PC are treated with androgen deprivation therapy (ADT) using luteinizing hormone-releasing hormone agonists and antagonists as first-line therapy. The majority of PC patients develop a castration-resistant PC (CRPC), which eventually leads to high mortality with poor prognosis, despite new targeted therapies. However, given that oligometastatic recurrence may enable local therapy in CRPC, accurate detection of metastatic lesions may improve clinical outcomes in patients with CRPC. Case Report: We report the case of an 83-year-old man with CRPC. 18Fluorine-prostate-specific membrane antigen-1007 positron emission tomography/ computed tomography (18F-PSMA-1007 PET/CT) revealed weak physiological PSMA accumulation in the prostate and strong accumulation not only in the internal iliac lymph node but also in the two obturator lymph nodes that could not be detected with conventional CT or magnetic resonance imaging. Prostatic re-biopsy revealed no prostate malignancy. Under the diagnosis of oligometastases in the pelvic lymph nodes, the patient underwent laparoscopic pelvic lymph node dissection, which revealed lymph node metastases in two obturator lymph nodes and the internal iliac lymph node, corresponding to the PSMA accumulation sites. The patient experienced at least 7 months of recurrence-free duration without additional treatment. Conclusion: This study indicates a novel approach to oligometastatic CRPC by means of accurate staging with 18F-PSMA-1007 PET/CT.