After ROC analysis to calculate the cut-off value of PSA fluctuation rate on the basis of the presence or absence of prostate cancer, the cut-off values was − 0.176 for patients with a PSA value fluctuation rate < 0 and was 0.180 only for patients with a PSA value fluctuation rate ≥ 0. The gene discussed is KLK3; the disease is Familial prostate cancer.