New test showing promise

No tumors show up in about 80 percent of prostate biopsies done today.
WASHINGTON POST
WASHINGTON -- An experimental blood test for prostate cancer may help eliminate tens of thousands of unnecessary biopsies at the same time that it detects many tumors that are now missed by the test commonly in use, its developers said Wednesday.
PSA, the current test, measures a protein normally produced by the prostate, while the experimental one, called EPCA-2, detects a chemical made principally in cancerous tissue.
Prostate cancer, the most common malignancy in men, is one of the more perplexing areas of medicine. Physicians are unsure how to find it and when to treat it.
Today, about 80 percent of prostate biopsies find no tumor -- a percentage that is rising as physicians become more aggressive in searching for the disease.
"We hope this will minimize the number of unnecessary biopsies," said Robert Getzenberg, a molecular biologist at Johns Hopkins Hospital who developed the new test, which is still under study and not yet commercially available. A description of it appears today in the journal Urology.
"It's an exciting new marker," said Martin G. Sanda, a urologist at Harvard Medical School. "There certainly is a need for a better test than PSA. Everyone accepts that."
His view was echoed by Gerald Andriole, chief of urology at Washington University School of Medicine, who said that "if the data hold up, this marker will be a substantial improvement over PSA."
Significance
The PSA test casts a net that is both too big and too full of holes. Finding a replacement that catches fewer healthy men, but more of those who do have cancer, would help settle at least one of the clinical conundrums concerning prostate cancer.
The test is being developed by researchers at Johns Hopkins Hospital and a Seattle biotech company called Onconome. It could be commercially available in 2008.
About 230,000 American men are diagnosed with prostate cancer each year, and about 30,000 die of it. The death rate is 2.5 times higher in blacks than in whites.
At the moment, men are screened for it in two ways -- by rectal exam and by the PSA (prostate-specific antigen) test. If a doctor feels a lump or the PSA is above 2.5 (nanograms per milliliter of plasma), most physicians will suggest a biopsy.
EPCA-2 is a protein that is part of the "nuclear matrix," the scaffolding inside a cell's nucleus that helps it copy its genes. The Hopkins researchers measured it in different groups of men whose cancer status was known.
They tried it on 30 men with PSA readings above 2.5 in whom biopsies found no cancer. All had normal EPCA-2 readings (below 30 nanograms per milliliter). This suggested that the test might eliminate many of the "false-positive" PSA results -- readings that are abnormal but apparently don't denote cancer.
Advantages
On the other hand, EPCA-2 appears able to detect cancer even when the tumor is small. It identified 36 out of 40 men who had cancer confined to the prostate gland and 39 out of 40 men in whom the tumor had spread. It also detected many men -- 14 out of 18 -- who had cancer but whose PSAs were normal.
This last group is especially worrisome to physicians. A study published three years ago found that about 12 percent of men with normal PSA readings actually have cancer.
The new test is not perfect, though.
Getzenberg and his colleagues tried it on 35 men with severe "benign prostatic hypertrophy" -- enlargement of the prostate that sometimes makes the PSA go up but isn't cancer. In eight of them the EPCA-2 was high, suggesting that the EPCA-2 test would flag some who turn out not to have cancer -- although probably not as many as PSA does.