KLK3 and posterior cortical atrophy: Explanations for the lack of mortality reduction seen with PSA screening in the PLCO trial include: 1) contamination of the control group, as 40 to 52% of patients in the usual care arm received PSA screening; 2) elimination of PCa cases prior to randomization, as 44% of patients had undergone one or more PSA tests prior to randomization; 3) no PSA threshold for biopsy (PSA results were reported to primary care physicians and a “community standard” for biopsy was applied at various centers), while the ERSPC authors used PSA cutoffs of 2.5 and 3.0 ng/mL, which was likely more sensitive.