Very large randomised controlled trials of PSA-based prostate cancer screening have been performed; these are summarised in a recent systematic review in 2018 that showed a small potential reduction in prostate cancer specific mortality with no change in all-cause mortality and an increased risk of complications from biopsy, overdiagnosis of clinically insignificant prostate cancer, and overtreatment [6–8]. Here, KLK3 is linked to prostate cancer.