Study: New prostate Ca test is more specific, sensitive than PSA

A still-investigational prostate cancer test that measures PSA as well as six specific antibodies found in the blood of men with the disease is more sensitive and more specific than the conventional PSA test, say researchers from UCLA’s Jonsson Comprehensive Cancer Center.

The test, called the A+PSA assay, also reduces the rate of false-positives, said senior author Gang Zeng, PhD.

"This is a very promising new approach," Dr. Zeng said. "Instead of using just one parameter, PSA, to test for prostate cancer, we use multiple parameters that can be measured in a single reaction."

In their retrospective study, Dr. Zeng, Allan Pantuck, MD, MS, and colleagues used blood taken before surgery from 131 patients from UCLA, Japan, and France with biopsy-confirmed prostate cancer and compared results with blood taken from 121 men with either BPH or prostatitis. The study focused on six specific prostate cancer-associated antigens that are found predominantly in patients with prostate cancer and not in those with benign prostate conditions.

The A+PSA assay looked simultaneously for PSA and antibodies to the six prostate cancer-associated antigens in a single reaction test done in a laboratory, much like PSA is measured. The new test takes about 2 hours, again similar to the PSA test. The test results in an index of numbers used to diagnose cancer, with a score of 0 to 0.5 indicating a benign result and 0.5 to 1 indicating the presence of prostate cancer, Dr. Zeng said.

In the new test, sensitivity was 79% compared with the 52% found in PSA testing. Specificity was 84% compared with the 79% found when testing for PSA alone. The rate of false positives using conventional PSA testing is 21%, while the rate with the new A+PSA assay is 16%, Dr. Zeng said.

"I think we have a test that has great potential to improve the diagnosis of prostate cancer," Dr. Zeng said. "I knew it would be better than the classic PSA test, but I was amazed at how much better it really was in this study."

Results from the study appear in the Journal of Translational Medicine (2011; 9:43).