KLK3 and neoplasm: The analysis did not reveal any significant correlation between the number of CTCs and serum PSA levels (r = -0.11, p = 0.63), tumor volume (r = 0.16, p = 0.49), tumor % (r = 0.09, p = 0.70), or grade group (r = 0.10, p = 0.49) (S3 Table in S1 File).