This contrasts to the strong relationship between PSA and ISUP ≥ 2 cancer, supporting previous observations that that ISUP ≥ 2 cancer is more likely to leak PSA into the blood than ISUP 1 cancer.[12] Most of these ISUP 1 cancers are likely to be clinically insignificant and illustrate the problem of over-diagnosis. Here, KLK3 is linked to cancer.