Prostate cancer screening only benefits men with elevated PSA
MedWire News: Continued prostate cancer screening among men aged 55-74 years is only beneficial if they have an initially elevated prostate-specific antigen (PSA) level, show the results of a Dutch study.
In men with an initially low PSA level, of 1.9 ng/ml or less, "the benefits of continued aggressive investigation and treatment may be limited," report Pim van Leeuwen, from Erasmus MC University Medical Center in Rotterdam, The Netherlands, and colleagues, who warn that mass screening can provoke large increases in cumulative prostate cancer incidence, overtreatment, and costs.
The team compared the incidence of prostate cancer and the rate of prostate cancer mortality in two cohorts of men who underwent PSA testing.
The first cohort included 43,987 men (intervention population) from the screening arm of the European Randomized Study of Screening for Prostate Cancer. The second included 42,503 men (clinical population) who underwent screening in Northern Ireland between 1994 and 1999.
Median follow-up lasted a respective 8.8 and 9.1 years for the intervention and clinical populations, during which time 9.9% and 3.6% of men were diagnosed with prostate cancer.
Men were grouped according to their PSA level at entry (0.0-1.9, 2.0-3.9, 4.0-9.9, or 10.0-19.9 ng/ml) and prostate cancer incidence rates increased with increasing PSA level. Incidence ratios among men from the intervention and clinical populations in the highest PSA group were 21.67 and 21.48 times those of men in the lowest PSA group.
The same trend emerged for prostate cancer-specific mortality rates; the absolute difference was 0.05 per 10,000 person years in men with the lowest baseline PSA, and 8.88 per 10,000 person years in men with the highest baseline PSA.
Risks associated with too-early detection were illustrated using numbers needed to investigate (NNI) and numbers needed to treat (NNT) to spare one death from prostate cancer. Both figures were higher for men with low rather than high PSA levels at baseline.
Specifically, NNI varied from 24,642 to 133 men in the lowest versus the highest PSA groups, and NNT varied from 724 to 60 men in the same groups.
"In other words, the greatest benefits of early detection programs may be when men, aged 55-74 years, are diagnosed and treated when their serum PSA level is in the range of 4.0 to 9.9 ng/ml or 10.0-19.9 ng/ml," conclude van Leeuwen et al in the journal Cancer.
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By Sarah Guy