KLK3 and prostate cancer: Findings from a study involving 419,582 British men aged 50 to 69 years - the Cluster Randomized Trial of PSA Testing for Prostate Cancer (CAP), which was conducted at 573 primary care practices across the United Kingdom, do not support single PSA testing for population-based screening and suggest that asymptomatic men should not be routinely tested to avoid unnecessary anxiety and treatment (3).