KLK3 and Familial prostate cancer: [68Ga]Ga-PSMA-11 has shown a high sensitivity for tumor localization in the setting of biochemical recurrence (BCR) of prostate cancer in various recent prospective studies; however, there remains a non-negligible number of patients with BCR and negative [68Ga]Ga-PSMA-11 PET/CT, particularly in patients with low PSA levels [11–14].