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Study of PSA Screening Strategies Looks to Reduce Risks
FP Expert Says Findings Support Changing How Screening is Used
By Matt Brown
- A modeling study indicates that "smarter" use of prostate-specific antigen (PSA)-based screening for prostate cancer may reduce risks associated with the test.
- The study authors based their conclusions on a comparison of 35 PSA screening strategies used in U.S. and European trials.
- An accompanying editorial and a family physician expert agree, however, that the study's results are not likely to change clinical practice.
- a reference strategy that screens men ages 50-74 years annually with a PSA threshold for biopsy referral of 4 mcg perL reduces the risk for prostate cancer death to 2.15 percent, while yielding a 3.3 percent risk of overdiagnosis;
- a strategy that uses a higher PSA threshold for biopsy referral in older men achieves a similar risk for prostate cancer death (2.23 percent) but reduces the risk for overdiagnosis to 2.3 percent; and
- a strategy that screens biennially, with longer screening intervals for men with low PSA levels, achieves similar risks for prostate cancer death (2.27 percent) and overdiagnosis (2.4 percent), but reduces total tests by 59 percent and false-positive results by 50 percent.
In an accompanying editorial, John Concato, M.D., M.P.H., an internist at the Veterans Affairs Connecticut Healthcare System in West Haven, says the limitations of the analysis leave questions unanswered and dilute its ability to inform the PSA screening debate.
"The model itself is mathematically meticulous and conceptually interesting, and the conclusions are reasonable -- but the corresponding clinical relevance is limited," Concato notes. "The results, presented as tradeoffs and involving calculations that often differ by only a fraction of a percentage point, are not likely to change clinical practice."
USPSTF Co-vice Chair Michael LeFevre, M.D., M.S.P.H., echoes Concato's sentiment, telling AAFP News Now that the study doesn't add any new information to what physicians and researchers already know about the benefits and harms of prostate cancer screening.
"Bottom line, the task force reached the conclusion that the potential benefit of prostate cancer screening does not outweigh the harm and this study certainly does not change that," LeFevre says. "It is also important to remember that (the authors of the Annals study) didn't actually study anybody. It is just a mathematical exercise, and it supports what is intuitively obvious: Screen less, biopsy less, and do less harm."
LeFevre, who is a family physician in Columbia, Mo., contends that the study supports the notion that physicians can lower the harms of prostate cancer screening by changing the way screening is used -- either by raising the threshold for biopsy, changing the frequency of screening or by putting an age cutoff on screening. However, although any one of those things is likely to reduce the harms associated with prostate cancer screening, physicians still do not know how doing those things would increase what is considered to be a very small possibility of benefit.
"The results from the U.S. and European studies were mixed," LeFevre says. "The European study showed a very small benefit, and the U.S. trial showed none.
"For those who continue to screen, a higher threshold for biopsy or less frequent testing will result in fewer false-positive results and less overdiagnosis and, therefore, reduce the harm."
Study Looks to Reduce PSA Screening Risks