Prostate specific antigen (PSA) is a protein produced by the prostate gland. It is measured in the blood stream and is a useful tool for following men who have been treated for prostate cancer. Does a PSA elevation after radiation treatment, be it a prostate seed implant and/or external beam radiation therapy, always signify disease recurrence?
In the past, a PSA elevation after a prostate seed implant or external beam radiation therapy was considered to be a harbinger of a prostate cancer relapse, often prompting expensive tests and invoking a great deal of patient anxiety. Then, when the PSA level climbed to10 ng/ml or greater, men were placed on hormonal therapy. Since the latter is associated with a number of unpleasant side effects, it is desirable to refrain from using hormonal therapy unless necessary. The question then arises: when does an increase in the PSA level not signify that cancer has returned?
There is a phenomenon known as a PSA bounce, in which the PSA level jumps up within one to three years after the man has completed radiation therapy. The PSA level eventually returns to the baseline it attained just after treatment. PSA bounce may be caused by death of the damaged cancer cells that release their PSA.
A PSA bounce usually begins with less than a one-point (less than 1 ng/ml) rise in the PSA level. Also, elevations of the PSA level after three years are less likely to be part of a bounce, and unlike a bounce, rises of the PSA level by more than 1.2ng/ml are less likely to drop back to their starting points.
A recent study collected data on 7,500 men who were treated for prostate cancer with radiation therapy. Nearly half of these men were found to have a PSA bounce. However, there was no adverse effect on their survival. In fact, these men fared just as well as men whose PSA did not bounce. Also, patients who show such a PSA bounce less than two years after treatment may be less likely to have cancer return later.
More good news is now that physicians are aware that an elevation in the PSA level does not necessarily mean prostate cancer has recurred, men whose PSA bounces after radiation therapy can be followed by their doctors, who can repeat the PSA blood test six months later.