Altered Glucose Metabolism Postchemotherapy Precedes PSMA Expression in Poorly Differentiated Prostate Cancer

A 73-year-old man presented with gastric lesion on upper endoscopy, biopsy-proven as poorly differentiated carcinoma. Staging FDG PET/CT scan showed gastric, intraprostatic, nodal, and extensive osseous lesions. Prostate-specific antigen levels were greater than 1000. The patient was treated as metastatic poorly differentiated prostate cancer with chemotherapy. Posttherapy 18 F-PSMA-1007 and FDG PET/CT scans were obtained. PSMA PET/CT scan revealed extensive disease similar in appearance as staging FDG PET/CT scan, indicating no apparent treatment response. FDG PET/CT scan showed partial metabolic response, correlating with improved prostate-specific antigen levels. This case indicates that chemotherapy-induced changes in glucose metabolism likely precede change in PSMA expression in poorly differentiated prostate cancer.