A study involving more than 7,500 men with prostate cancer treated with radiation concludes that a rise in the PSA level after treatment--called PSA bounce--does not have clinical relevance and does not affect survival. The results of this multi-institutional study will be presented today at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology in Philadelphia.
"Radiation oncologists and urologists have been observing the PSA bounce for several years without knowing for sure if it had any clinical significance," explained Eric Horwitz, M.D., clinical director of the Radiation Oncology Department at Fox Chase Cancer Center and author of the study. Now we have a large body of evidence showing it doesn't."
PSA, or prostate specific antigen, is measured by a blood test and used to determine if prostate cancer is present.
One key endpoint of the study was to determine if there was a survival difference between the patients who experienced a PSA bounce and those who did not. The data evaluated were from two multi-institutional pooled datasets--4,839 patients (9 institutions) with early prostate cancer treated with external-beam radiation alone and 2,693 patients (11 institutions) treated with seed implants. The datasets for these men spanned an average of 10 years.
Of those who experienced a PSA bounce, 902 patients were treated with external-beam therapy and 470 patients were treated with seed implants, also known as brachytherapy. A PSA bounce was defined as an increase of at least 0.2 ng/ml over a previous PSA measurement followed by a decline.
"A significant number of men experienced at least one PSA bounce after treatment, usually within one to three years after treatment," said Horwitz. "However, after 10 years, there were no statistical differences in overall survival of patients who had a bounce and those who did not."
Horwitz said the study also showed no difference between the two groups regarding other clinically important endpoints, including biochemical failure (PSA level after treatment), distant metastasis-free survival and cause-specific survival. Biochemical failure was determined by the newest method--Nadir +2.