KLK3 and bone metastasis: Hori et al. reported that PSA nadir < 1 ng/mL and TTN > 12 months was associated with a low risk of biochemical relapse in PCa patients with bone metastasis, whereas patients without bone metastasis with a PSA nadir < 0.1 ng/mL and TTN > 24 months had a low risk of biochemical relapse [31].