Studies highlight inefficacy of PSA test

PSA levels, a protein made by the prostate gland, increase not only when a tumor develops, but also under benevolent conditions, the studies revealed.

PSA does not distinguish lethal and innocuous cancers
Dr. Mattias Johansson of the International Agency for Research on Cancer in Lyon, France and co-author of one of the studies averred, "In particular, tools that help distinguish rapidly growing and potentially lethal tumors from slow growing tumors are warranted in order to minimize over diagnosis and over treatment."

For the purpose of the study, researchers analyzed 500 men with prostate cancer and over 1000 cases without the disease but with similar characteristics.

The study found that the PSA could not dependably differentiate between slow-growing innocuous prostate cancers from those who could grow aggressively and prove lethal.

"We know these limitations lead to false-positive results, overdiagnosis and overtreatment, but the psychological and financial costs of PSA testing for the early detection of prostate cancer have not yet been measured precisely enough to determine if they outweigh a modest benefit in survival associated with screening," said Jennifer Stark, a research fellow at Harvard School of Public Health in Boston.

Not a fool proof test
The other study analyzed 540 men with prostate cancer and 1,034 men without prostate cancer. The findings suggest that no cut-off level for PSA could be declared as a criteria required for a screening test.

Benny Holmstrom, a urologist with Gavle Hospital in Gavle, Sweden, and lead author of the study noted, “Our findings strongly indicate that, in addition to PSA, further biomarkers are needed before inferring population-based screening for prostate cancer.”

Holmstrom said, “We found that in men with a prediagnostic PSA level below 1 nanogram per milliliter, only six men [1.2 percent] were later diagnosed with a high-risk prostate cancer. Hence, PSA levels below that almost ruled out a future high-risk prostate cancer diagnosis."

Men have been advised to discuss with their doctor whether or not they should have a PSA test. The doctor should fully inform the patient of the benefits, harms, and uncertainty associated with the test.

Give the current status of research on the subject doctors too face contradictory evidence about the intrinsic worth of screening and the usage of PSA as a screening tool.

The two studies appear in the Sept. 25 online edition of BMJ.