KLK3 and prostate cancer: While there is limited epidemiological evidence for other lifestyle risk factors for prostate cancer (WCRF/AICR, 2014), the relatively high variation in incidence rates worldwide suggests that differences in exposure to environmental factors may have a role in prostate cancer development, although some of the variation is due to differences between countries in prostate-specific antigen (PSA) testing (Ferlay et al, 2015).