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April 20, 2010 (Washington, D.C.) -- Researchers are developing a new blood test to help identify which men with early prostate cancer can forgo immediate treatment.
In a small preliminary study, the test proved 70% accurate in predicting which men had more aggressive tumors that require treatment.
The results have yet to be replicated, a necessary step before acceptance by the medical community.
But the test shows promise for safely identifying men who can undergo active surveillance -- close monitoring for signs of tumor growth -- rather than treatment, says Robert W. Veltri, PhD, an associate professor of urology and oncology at Johns Hopkins University.
"The goal of the new test, which measures blood levels of three different forms of PSA, is to determine who will and who will not progress and require treatment," Veltri says.
The findings were presented at the annual meeting of the American Association for Cancer Research.
To treat or not to treat is one of the most difficult dilemmas facing men with prostate cancer, especially men with early, localized cancer that is contained within the prostate, when it is curable.
Because prostate cancer often grows so slowly it may never become life-threatening, many of these men, particularly older men, may die of other causes before the prostate cancer causes problems. But in some men, the cancer will spread beyond the prostate without treatment. Then it may no longer be curable.
As a result, there has been a long-running debate in the medical community about the value of treatment to destroy cancer cells vs. active surveillance, also known as watchful waiting.
Watchful waiting consists of close monitoring with periodic digital rectal exams, yearly biopsies, and PSA (prostate-specific antigen) blood tests.
Rising PSA levels can be a sign of prostate cancer spread in men with early cancer. But the PSA test can't distinguish between slow-growing and aggressive cancers, Veltri tells WebMD.
"Because of PSA, there is overdiagnosis and overtreatment of prostate cancer," he says.
The new blood test, known as the Prostate Health Index (PHI), measures three forms of PSA, including pro-PSA. Pro-PSA is a shortened molecule that is missing a few of the amino acids that make up the PSA protein. It's the most accurate form of PSA, Veltri says.
The federally funded study involved 71 men who were diagnosed as having small, low-grade, and low-stage prostate cancer based on their PSA results. At the time of their diagnosis, their blood had been banked.
By an average of nearly four years later, 39 had unfavorable biopsy results that signaled a need for treatment.
The PHI test was performed on blood samples from all 71 men.
"When we combined the [biopsy results] and the serum Prostate Health Index, we were able to predict seven in 10 men that might progress," Veltri says.
Veltri says the PHI test won't replace biopsies but will hopefully allow men to have them every other year instead of year.
His lab is now conducting an expanded study to look for other biomarkers that may predict aggressive cancers.