KLK3 and posterior cortical atrophy: According to the results obtained in the present study with limited numbers of PCa and control patients who underwent repeated biopsy in our university hospital, the risk that the first biopsy was a false negative was 14 times higher in patients with than in those without an increased frequency of P. acnes-positive glands in their biopsy samples, and the risk assessment power with the first negative biopsy samples was superior to the serum PSA titer of patients at the time of the first biopsy.