MONDAY, March 10 (HealthDay News) -- Changes in medical practice have undermined the value of the prostate-specific antigen (PSA) test as a diagnostic tool for prostate cancer, a new study asserts.
However, that assertion was immediately challenged by other experts in the field.
The American Cancer Society recommends annual screening for prostate cancer for most men after age 50. The screening is done in two steps: a digital rectal exam, followed by a blood test for PSA, a protein produced by the prostate gland.
"In men with an abnormal digital rectal examination, it [the PSA test] still is very predictive," said study author Dr. Douglas S. Scherr, clinical director of urological oncology at Weill Cornell Medical Center in New York City. "For men with a normal digital rectal examination, it has lost the predictive accuracy it had in the 1990s."
For those men, exact PSA readings matter less, because doctors are doing more biopsies now and are using improved biopsy techniques, Scherr explained. His report was expected to be published in the April 15 issue of Cancer. In a retrospective analysis, his team looked at 1,607 prostate biopsies performed at Weill Cornell between 1993 and 2005, and uncovered several trends.
In the 1990s, biopsies generally were limited to men with PSA readings higher than 4 nanograms per milliliter of blood. Later, they were often done when the PSA levels were between 2.5 and 4, Scherr said.
"In the early and mid-90s, we used six needles when we did a biopsy," he said. "Now, we stick in 14. Taking more cores and doing biopsies at lower PSA levels has allowed us to keep the prostate cancer detection level steady. If we kept the PSA level at 4 rather than at 2.5, the cancer detection rate would have fallen rapidly."
Increased awareness of prostate cancer has also changed the screening picture, Scherr said. "You almost never have an abnormal rectal examination these days," he said.
There is a need to develop new biomarkers for prostate cancer beyond PSA, Scherr said. "Should a man when he turns 50 have a biopsy?" he said. "It is certainly an important question that needs being looked at."
