It's a newer version of the prostate-specific antigen (PSA) test. The older version wasn't so bad. It vastly helps doctors find prostate cancers while they're still small and curable. But a bad PSA finding doesn't necessarily mean cancer.
Most of the time, biopsies don't find any cancer in men with alarming PSA test results. The new test won't find more cancers. But it will cut down on these so-called false positives, according to a study led by Alan W. Partin, MD, PhD, Bernard L. Schwartz distinguished professor of urologic oncology and professor of urology, pathology, and oncology at Johns Hopkins Medical Institute.
"The problem with the PSA test is we biopsy way too many people to find that person who does have prostate cancer," Partin tells WebMD. "We are not missing the cancers that are out there. But 75% of biopsied people don't have cancer. This newer test cuts down on that somewhat. This is the most cost-efficient way to use PSA testing."
Prostate Cancer Detection Technology Advances
PSA is a chemical signal released from the prostate. When the prostate isn't healthy, there's more PSA floating around in a man's system. Current tests measure the total PSA -- tPSA -- in the blood. But men with prostate cancer tend to have more of their PSA bound to a specific protein in the blood. The new test measures this complexed PSA or cPSA.
The test is already available, but labs don't always use it. Partin's study may change that. His team collected data from 831 men at seven prostate cancer treatment centers. All of the men were sent for biopsies based on the older tPSA test. They also underwent cPSA tests.
The results of the cPSA tests were compared with the results of the tPSA tests of those men diagnosed with prostate cancer. The researchers found that the cPSA test was more predictive of prostate cancer than the tPSA test.
At the lower, more ambiguous PSA levels, the cPSA test caught just as many cancers as the older test -- but there were fewer false positives. At the lowest PSA levels, about 14% of men would have avoided biopsies if they'd based their decision on the newer test. The findings appear in the November issue of The Journal of Urology.
"Right now this is one of the best prostate cancer tests we have," Partin says.
How much better is the new test? That depends on what you find most important, says medical oncologist Mayer Fishman, MD, PhD, of the Moffitt Cancer Center in Tampa, Fla. Fishman admits that he's biased. The prostate cancer patients that he treats all have advanced disease.
"Is the most important thing to decrease negative biopsies? I'd say no," Fishman tells WebMD. "We need to decrease the number of deaths. This new test does a reasonable job of reducing extra testing. But the most important thing is to find the cancers."
But he suggests that the new test might actually find more cancers -- if, by promising fewer biopsies, it motivates more men to get PSA tests.
"Will the general public be more motivated to get prostate testing when they understand the new test is better? That may resonate with some people," Fishman says. "It would be nice if we had more screening."
Partin's study was funded by Bayer, which manufactures the cPSA test.