Study Casts Further Doubt on PSA for Cancer Screening


In terms of likelihood ratios, PSA didn't attain numbers needed for a screening test

27 sept 2009-- Based on likelihood ratios, prostate specific antigen (PSA) concentrations at any cutoff value didn't meet the criteria needed for a screening test, according to research published online Sept. 24 in BMJ.

Benny Holmstrom, M.D., of Umea University in Sweden, and colleagues analyzed data from 540 cases of prostate cancer and 1,034 matched controls drawn from a longitudinal cohort study. Blood samples were taken from cases an average of 7.1 years before diagnosis. The researchers assessed the likelihood ratios of PSA concentrations in predicting later cancer diagnosis. A positive likelihood ratio above 10 is considered strong evidence for ruling in disease, and a negative likelihood ratio below 0.1 is thought to be sufficient for ruling out disease.

The researchers found that, at PSA cutoff values of 3, 4 and 5 ng/mL, the positive likelihood ratios were 4.5, 5.5 and 6.4, respectively. Negative likelihood ratios were 0.47, 0.61 and 0.70, respectively. However, the authors note that concentrations below 1.0 almost completely ruled out a later diagnosis of cancer, suggesting that this cutoff might help identify men with very low risk.

"Converting sensitivity and specificity into likelihood ratios would help clinicians to evaluate how effective the test might be in ruling in or ruling out the disease. Clinicians should consider using likelihood ratios together with a patient's individual risk factors for the disease to explain the potential benefits and harms of the PSA test, allowing patients to contribute to decisions," write the authors of an accompanying editorial.

The editorial authors are members of the Cochrane Prostatic Diseases and Urologic Cancers Group.

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Prostate specific antigen testing may be unnecessary for some older men

22 feb 2009--Certain men age 75 to 80 are unlikely to benefit from routine prostate specific antigen (PSA) testing, according to a Johns Hopkins study published in the April 2009 issue of The Journal of Urology.

The researchers found that men in this age group with PSA levels less than 3 nanograms per milliliter are unlikely to die of or experience aggressive prostate cancer during their remaining life, suggesting that the use of PSA testing in many older men may no longer be needed.

The study, led by researchers from the Johns Hopkins University School of Medicine and the National Institute on Aging's Baltimore Longitudinal Study of Aging (BLSA), reviewed data from 849 men (122 with and 727 without prostate cancer) who were participating in the BLSA and who had undergone regular PSA testing.

Results showed that among men who were over 75 with PSA levels less than 3 nanograms per milliliter, none died of prostate cancer and only one developed high-risk prostate cancer. In contrast, men of all ages with a PSA level of 3 nanograms per milliliter or greater had a continually rising probability of dying from prostate cancer.

If confirmed by future studies, these results may help determine more specific guidelines for when PSA -based screening might be safely discontinued, according to lead investigator Edward Schaeffer, M.D., an assistant professor of urology at Johns Hopkins. While PSA screening remains a useful tool for helping detect early stages of prostate cancer and is credited with decreasing prostate cancer mortality, discontinuing unneeded PSA testing could significantly reduce the costs of screening and also potentially reduce morbidity resulting from additional tests or treatments.

"We need to identify where we should best focus our health care dollars by concentrating on patients who can actually benefit from PSA testing," Schaeffer says. "These findings give a very strong suggestion of when we can start to counsel patients on when to stop testing."

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Other Johns Hopkins researchers who participated in this study include H. Ballentine Carter, M.D., Anna Kettermann, M.A., Stacy Loeb, M.D., Luigi Ferrucci, M.D., Ph.D., Patricia Landis, B.S., Bruce J. Trock, Ph.D., and E. Jeffrey Metter, M.D.