Bottom Line: A screening program that invited men to a clinic to undergo a single prostatespecific antigen (PSA) test increased detection of lowrisk prostate cancer but made no significant difference in prostate cancer deaths after 10 years.

Why The Research Is Interesting: Prostate cancer screening remains controversial because potential benefits may be outweighed by harms from overdetection and overtreatment. Current policy in the United Kingdom, where this clinical trial was conducted, doesn't advocate screening.

Who and When: 419,582 men from 573 primary care practices in the United Kingdom; recruitment started in 2001 and patient followup ended in March 2016.

Interventions and Measures: 189,386 men at 271 practices were invited to attend a PSA testing clinic and to receive a single PSA test while 219,439 men at 302 practices were unscreened in a control group for comparison (intervention); death from prostate cancer after about 10 years and secondary outcomes including cancer stage at diagnosis (outcomes).

How (Study Design): This was a randomized clinical trial. RCTs allow for the strongest inferences to be made about the true effect of an intervention. However, not all RCT results can be replicated in realworld settings because patient characteristics or other variables may differ from those that were studied in the RCT.

Results: The proportion of men diagnosed with prostate cancer was higher in the intervention (4.3%) group than control (3.6%) group, but there was no significant difference in prostate cancer mortality (intervention, 0.29% vs. control, 0.29%) after a median followup of 10years.

Study Limitations: A single PSA screening may fail to reflect a longterm effect of multiple PSA testing rounds; a followup of 10 years may be too short to identify the effect of screening.

Study Conclusions: The findings don't support single PSA testing for populationbased screening.