KLK3 and cancer: Furthermore, while our cohort consisted of men enrolled in the PLCO Cancer Screening Trial at the age of 55 to 60 years, we believe that previous work has provided population-based evidence for a younger target age for baseline PSA testing,30,39 which is currently being prospectively evaluated in the randomized ProBase trial, enrolling men at age 45 to 50 years for baseline PSA testing.40