A consortium of prostate cancer experts have discovered, through a clinical investigation, that prostate cancer patients who have a lower prostate specific antigen (PSA) score after radiation therapy to treat their cancer are less likely to have their prostate cancer return or spread to other parts of their body than patients with a higher PSA score.
The study was published in the March 15, 2006, issue of the International Journal of Radiation Oncology-Biology-Physics, the official journal of ASTRO, the American Society for Therapeutic Radiology and Oncology.
The study was conducted on nearly 5,000 patients treated with radiation therapy in nine prestigious academic radiation oncology departments across the United States. The participating institutions included the University of Michigan in Ann Arbor, Mich.; the M.D. Anderson Cancer Center in Houston; Fox Chase Cancer Center in Philadelphia; Cleveland Clinic Foundation in Cleveland; William Beaumont Hospital in Royal Oak, Mich.; Mallinckrodt Institute of Radiology in St. Louis; Mayo Clinic College of Medicine in Rochester, Minn.; Massachusetts General Hospital in Boston and Memorial Sloan-Kettering Cancer Center in New York.
After receiving radiation, most patients experience a decline in their PSA blood test score. Doctors measure the PSA level after radiation to monitor treatment response. If the PSA decreases and then stays relatively level, the treatment is considered a success, but if the PSA then rises, doctors may consider additional treatments for cancer recurrence.
In this study, researchers set out to examine whether or not a lower PSA score is a good indicator in predicting the likelihood that a patient’s prostate cancer will return or spread. In the current standard of care, doctors are less interested in the actual PSA score, but whether the PSA rises after treatment. A rise is used to gauge whether the cancer will likely return.
The doctors found that a lower PSA level was associated with a dramatic decrease in both prostate cancer recurrence and the spread of cancer among patients across all risk categories. The patients were separated into different categories, based on their PSA score after radiation. The patients with the lowest PSA scores experienced an eight year disease-free survival rate of 75 percent, compared with only 18 percent for those with the highest PSA scores. Patients who had the lower PSA scores also had a 97 percent distant metastasis-free survival rate, compared with 73 percent for those with the highest PSA scores. In addition, the researchers found that patients treated with a higher dose of radiation had a better chance of achieving a lower PSA score and were less likely to see their prostate cancer return.
“While there is no magic number for the PSA that guarantees that prostate cancer has been cured in an individual patient, in general, the lower the PSA number, the better chances that the cancer will not return or spread,” said Michael E. Ray, M.D., Ph.D., lead author of the study and a radiation oncologist at the University of Michigan Medical Center. “These findings may help us to identify high risk patients early. This may allow their doctors to consider other adjuvant or salvage therapies to hopefully increase their chances for survival.
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