KLK3 and prostate cancer: Targeting gastrin-releasing peptide receptor (GRPR) is thought to complement PSMA-negative prostate cancer (PCa) patients (58), and it is helpful for the localization of recurrent lesions in 18FECH PET/CT-negative patients (59).Another study showed that the detection rate of 18F-FDG PET/CT in PSMA-PET negative patients was 16.7%, and patients with PSA ≥2.3 ng/mL and high Gleason score were more likely to benefit from FDG PET (60).