Test for Prostate Cancer in the Works
Study Shows New Blood Test More Accurate Than PSA Test
Feb. 14, 2008 (San Francisco) -- A new blood test that measures a protein that is elevated in people with prostate cancer could spare thousands of men from unnecessary biopsies and risky treatments, researchers report.
The test, which homes in on a protein called human aspartyl (asparaginyl) beta-hydroxylase, or HAAH, adds to the accuracy of standard PSA testing for prostate cancer, says Stephen Keith, MD. Keith is president and chief operating officer of Panacea Pharmaceuticals Inc., in Gaithersburg, Md., which is developing the test and sponsored the study.
The PSA test measures levels of a protein known as prostate-specific antigen in the blood. High PSA levels may signal cancer.
The problem is that not everyone with a high PSA level has prostate cancer. And not everyone with prostate cancer has a high PSA level. This uncertainty leads to many unnecessary prostate biopsies -- and to many unnecessary prostate surgeries or radiation treatments.
"There's a big movement in the field to increase the accuracy of PSA," says Eric A. Klein, MD, head of urologic oncology at Cleveland Clinic.
"This is one of a number of promising tests," Klein tells WebMD. Klein is a spokesman for the American Society of Clinical Oncology (ASCO).
The findings were presented at the Genitourinary Cancers Symposium, which is co-sponsored by ASCO and two other cancer care organizations.
HAAH Adds to PSA Accuracy
The latest research involved 233 men with prostate cancer and 43 healthy men over 50 years old.
Results showed that the HAAH test had an overall sensitivity of 95%, meaning that 5% of prostate cancers were missed.
The specificity was 93%, meaning that the test gave false-positive results to 7% of people who didn't have the cancer.
In contrast, the sensitivity and specificity of PSA are only about 30% to 40%, Keith says.
Importantly, the HAAH test was accurate regardless of a man's PSA level, he adds.
The test may prove particularly useful for men with PSA scores between 2 and 4, Keith tells WebMD. Typically, doctors only refer men with PSA scores over 4 for biopsy.
"Men with PSA scores of 2 to 4 wouldn't normally be sent for a biopsy. If they have elevated HAAH levels, they should be," he says.
In men with PSA scores of 4 to 10, the addition of HAAH could decrease the number of unnecessary biopsies that show no cancer is present from about 75% to 10%, he says.
Panacea scientists plan to apply for FDA approval of the test, which costs about $125.
Prostate cancer is the second most common cancer among men. It is diagnosed in more than 218,000 men and claims more than 27,000 lives each year.