New Prostate Cancer Test Said More Reliable Than PSA Screening

While prostate cancer is the most common cancer among men, the standard detection test is often inaccurate, leading millions of men to get unnecessary biopsies. Researchers have devised a potentially better way to catch the cancer early.

Melvin Raider learned the hard way how the current test for prostate cancer can be unreliable.

Like most men in their 60s, Raider has a yearly PSA test, which measures the prostate specific antigen in the blood. A high level can be a sign of cancer.

When Raider's PSA level spiked, his doctors ordered a biopsy. But it showed he did not have cancer. In fact, 80 percent of PSA results are false alarms.

A group of researchers thought they could make improvements. They relied on arguably the most sensitive and accurate detection instrument ever developed -- the body's own immune system.

The immune system is normally thought of as the body's network for identifying and fighting harmful germs and viruses. But it also orchestrates a mammoth response to cancer, releasing thousands of chemicals into the bloodstream to destroy the tumor.

The new blood test looks for 22 of these chemicals that specifically fight prostate cancer. Detection of these chemicals seems to be a much more reliable indicator than the PSA test, which measures just one chemical that may or may not indicate cancer.

"These 22 markers ended up being the best combination of markers that allow us to most effectively diagnose prostate cancer," said Dr. Arul Chinnaiyan, assistant professor of pathology and urology at the University of Michigan Medical School.

Compared to the PSA results, preliminary findings show the rate of false alarms with the new prostate blood test is only about 12 percent.

"We're very excited about this test," said Dr. Mark Rubin, chief of urologic pathology at Brigham and Women's Hospital in Boston. "This represents a new paradigm, a new way to look at cancers."

If the blood test lives up to its potential in larger studies, it could be available within a few years -- not just for prostate cancer -- but for lung and breast cancers, as well.

ABC News' John McKenzie filed this report for "World News Tonight."