Prostate cancer patients who have a prostate-specific antigen (PSA) value of less than or equal to 1.5 at two years after external beam radiation therapy (EBRT) are less likely to have a cancer recurrence and cancer-related death, according to a study in the December 1 issue of the International Journal of Radiation Oncology*Biology*Physics, the official journal of the American Society for Radiation Oncology (ASTRO).
PSA levels in a prostate cancer patient are monitored after a patient's treatments, and after a successful course of EBRT the levels should decline gradually over the following 18 to 24 months. A continued rise in PSA can indicate relapsing disease.
Prior studies have attempted to categorize PSA response patterns after treatment in an effort to identify patients with an increased chance of a relapse earlier; however, most did not use a fixed point after treatment to predict outcomes.
Researchers at the Memorial Sloan-Kettering Cancer Center department of Radiation Oncology and Epidemiology and Biostatistics in New York, sought to determine the significance of a patient's reaching a certain PSA level at a specific point in time after EBRT.
The study authors found that patients with a PSA value of less than or equal to 1.5 at two years had a 2.4 percent incidence of distant metastases at five years after treatment and a 7.9 percent incidence at 10 years after treatment. Patients with a PSA value higher than 1.5 experienced a significantly higher rate of metastases at five and 10 years after treatment (10 percent and 17.5 percent, respectively).
"In the past, patients with a relapsing cancer after receiving radiation were not identified until several years after treatment and at that point it may be too late to effectively salvage their recurrence," Michael Zelefsky, M.D., lead author of the study and a radiation oncologist at Memorial Sloan-Kettering Cancer Center, said. "If we can catch these future instances of cancer recurrence earlier in prostate cancer patients, then we have a much higher chance of reducing the mortality associated with the cancer."
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