Prostate cancer patients with a lower prostate-specific antigen level after radiation therapy are less likely to develop recurrent or metastatic disease than peers with a higher level, according to an article in the March 15 issue of the International Journal of Radiation Oncology*Biology*Physics.

The study was conducted on nearly 5,000 US patients treated with radiation therapy in nine academic radiation oncology departments.

In the current study, researchers found that a low level after completion of therapy was associated with a dramatic decrease in both prostate cancer recurrence and spread of cancer among patients across all risk categories.

The patients were separated into different categories based on prostate-specific antigen level after radiation. Men with the lowest levels experienced an eight-year disease-free survival rate of 75 percent compared with only 18 percent for those with the highest levels after completion of treatment.

Patients who had lower levels also had a 97 percent distant metastasis-free survival rate, compared with 73 percent for men with the highest levels. In addition, patients treated with a higher dose of radiation had a better chance of achieving a low prostate-specific antigen level and were thus less likely to see their disease return.

“While there is no magic number for the prostate-specific antigen level that guarantees that prostate cancer has been cured in an individual patient, in general, the lower the number, the better chances that the cancer will not return or spread,” said Michael E. Ray, MD, PhD, 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.”