Long-term follow-up of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO) confirmed earlier results showing no reduction in prostate cancer mortality with yearly prostate-specific antigen (PSA) testing. A high rate of PSA testing in the study’s control group suggests there is no benefit to organized screening as compared with opportunistic screening.
“Although screening for prostate cancer with PSA has been ongoing for more than 25 years, it is still not clear whether such screening reduces prostate cancer mortality and, if so, whether the benefits outweigh the established harms,” wrote study authors led by Paul F. Pinsky, PhD, of the National Cancer Institute in Bethesda, Maryland. Two large trials have yielded conflicting results on the utility of PSA screening, and because PSA often fails to distinguish between dangerous and indolent prostate tumors, the potential harms of overdiagnosis and overtreatment are substantial.
The new trial extended the results of PLCO, including 38,340 men randomized to undergo yearly PSA testing for 6 years and 38,343 in a control group. The median follow-up for the 2 groups was 14.8 and 14.7 years, respectively; the results were published in Cancer.
Over a total of 533,014 person-years in the intervention group, there were 255 prostate cancer deaths. Over the 529,860 person-years in the control group, there were 244 prostate cancer deaths. This yielded a rate ratio of 1.04 (95% CI, 0.87–1.24; P = .67). All-cause mortality was also similar between the groups, with a rate ratio of 0.977 (95% CI, 0.950–1.004; P = .11).
Substantial numbers of men who were not randomized for PSA screening did undergo PSA tests at some point during the screening period or follow-up period. Estimates suggest that 86% of men in the control arm underwent at least one PSA test, and 99% of intervention patients underwent a PSA test. The high testing rate in the control arm, the authors noted, suggests there is no benefit of organized screening as compared with opportunistic screening.
Most prostate cancer deaths in the trial occurred in cases diagnosed during the screening phase (first 6 years). “This indicates the need for long-term follow-up, perhaps even longer than 15 years, to fully capture the potential mortality effects of PSA screening,” the authors wrote.