KLK3 and Familial prostate cancer: <h4>Background</h4>Positron emission tomography/computed tomography (PET/CT) using prostate-specific membrane antigen (PSMA)-targeted radiotracers labeled with zirconium-89 (<sup>89</sup>Zr; half-life ~ 78.41 h) showed promise in localizing biochemical recurrence of prostate cancer (BCR) in pilot studies.<h4>Methods</h4>Retrospective analysis of 38 consecutive men with BCR (median [minimum-maximum] prostate-specific antigen 0.52 (0.12-2.50 ng/mL) undergoing [<sup>89</sup>Zr]Zr-PSMA-617 PET/CT post-negative [<sup>68</sup>Ga]Ga-PSMA-11 PET/CT.