PROSTATE SPECIFIC ANTIGEN (PSA)
EXPLANATION IN PATIENTS WITH PROSTATE CANCER AFTER RADIATION THERAPY

WHAT IS PSA, AND HOW DO WE MEASURE IT?
Prostate Specific Antigen is a protein that is unique or specific to the prostate. Normal prostate cells and almost all prostate cancer cells make PSA.  While most PSA is locked in the individual prostate cell (and in semen), some normally  'leaks' into the blood stream (serum).  PSA is not harmful.  These PSA levels can be measured in an individual's serum and with this information we are judge the success of treatment of prostate cancer. 

If prostate cancer spreads away from the prostate gland it will almost always continue to make PSA.  A rising PSA is usually a sign of growth of the prostate cancer.

WHAT IS THE SIGNIFICANCE OF OTHER TYPES OF PSA IF I HAVE PROSTATE CANCER?
Free PSA, Complex PSA (PSA-ACT), hK2 and other new PSA screening tests have no benefit over the currently used PSA tests in patients who already have a diagnosis of prostate cancer. They are helpful only in screening situations in helping us determine who needs or does not need a biopsy.

AFTER RADIATION THERAPY (EXTERNAL BEAM OR IMPLANT)
After any form of radiation therapy for localized prostate cancer the prostate gland is left in place. Therefore the PSA level may not become unmeasurable. This is not unexpected and reflects the presence of remaining non-cancerous prostate tissue which also releases PSA into the blood stream. We do expect the PSA level to fall, however, to a very low level and stay there.

Currently, no exact level has been established as the expected 'break-point' of success. Some use 0.2 some use 0.5, some 1.0 and some set not exact level but say that whatever the PSA falls to after treatment is the baseline and as long as the level doesn't rise from that point on two consecutive measurements that success has been achieved. If the PSA level starts rising after radiation therapy from whatever baseline is established, the possibility of recurrence of the prostate cancer must be suspected. Whether this recurrence is in the prostate gland itself or whether it is somewhere else in the body cannot not be determined by the PSA test--only that the prostate cancer cells are somewhere.


BENIGN PSA 'BOUNCE' AFTER IMPLANTATION
Between 8 months and 2 years after seed implantation a slight rise or 'bounce' of PSA measurement may occur in 3 out of every 10 patients. This BENIGN rise is not easy to explain and may result from some form of prostate inflammation as the radiation dose begins to diminish. In these cases the PSA will usually fall again at the next interval. During this period, we have no way of being certain whether a single rise is due to recurrence of cancer or whether it is the benign bounce just described. We need to repeat the PSA at regular intervals, such as every three months, during this period. If the PSA rises three consecutive times, a recurrence of the cancer is strongly suggested.