“Dr. Peter Scardino's Prostate Book” 2006
Peter T. Scardino, M.D.
Chairman of the Department of Urology ant Memorial Sloan-Kettering Cancer Center
and Judith Kelman
PSA After Radiation page 394-395
After brachytherapy or external beam radiation, it’s difficult to determine the cause of a rising PSA. The prostate is not removed as it is with surgery. Any PSA we detect may be coming from benign overgrowth or inflammation of normal prostate tissue, not necessarily from cancer.
As radiation kills cancer cells, the PSA slowly declines until it reaches its lowest level, which we refer to as the PS nadir. During the course of radiation, the PSA may actually rise at first and not begin to fall until six months after the treatment course is finished. The average time it take to reach PSA nadir is eighteen months, but it can take as long as three years. Ideally, we want that lowest number to be 0.5 or less. The PSA rarely becomes undetectable as it does after radical prostatectomy. The nadir is predictive of how you’re likely to fare. The lower the PSA goes, the smaller the chance that your cancer will recur.
The American Society for Therapeutic Radiology and Oncology (ASTRO) defines radiation failure as a PSA that rises 2 ng per milliliter above the PSA nadir. 1
Using this definition, it’s possible to ignore a tumor recurrence for a very long time and miss a second chance for a cure. Ideally, the PSA should fall to a low and stay there. If it begins to rise from the lowest point, is higher than 1, and reaches three new peaks or highs, even if they’re not consecutive, I’d advise you to meet with your radiation oncologist and urologist to consider the next steps.
The purpose of the three-peak rule is to make sure the PSA increase is genuine. But if your level begins to rise above the nadir, I believe it’s prudent to wait three months—not six—to repeat the test with an eye to further assessment and possible treatment if you see three new peaks.
NOTE: Page 396
PSA can fluctuate for no reason from day to ay by as much a 36 percent for men who still have the gland in place after radiation therapy, so you’re bound to see some meaningless ups and downs. After surgery, the PSA should become undetectable and remain so.
PSA BOUNCE Page 404-405
Though the reason remains unclear, in 30 to 40 percent of brachytherapy patients and 5 to 15 percent of men who have received external beam therapy (without hormones), the PSA level goes up for a while and then falls again without any additional treatment. This PSA bounce tends to occur within the first three years. The level can rise long and steadily enough to meet the ASTRO definition of a radiation failure (see page 395). If this happens within the first two years, we have to consider that the PSA elevations we see might represent an innocent bounce that will spontaneously return to low levers. Of course, an early rise may continue, indicating recurrent cancer. The uncertainty of PSA levels after radiation can lead to a crucial delay in starting further, curative treatment. Normally, a bounce doesn’t go very high and the slope is gradual, but the phenomenon confounds our ability to diagnose a recurrence soon after radiation. 13
If the PSA begins to rise two to two and a half years after radiation therapy, a biopsy may be in order. If the results are negative, indicating no cancer, we would continue to follow the PSA and plot its doubling time. Since with radiation the prostate and surrounding tissues were not removed and examined (as they are after surgery), we have no way of knowing whether the cancer had already spread to the seminal vesicles or lymph nodes when you were first diagnosed. All we have to go on after radiation are your original PSA, the clinical stage and grade of your cancer at the time of biopsy, how low your PSA went after radiation (PSA nadir), the amount of time that elapsed after radiation before your PSA began to rise, and your PSA doubling time. A high-risk cancer with an initial Gleason grade of 8 to 10, a PSA over 10, and an extensive tumor points to a higher risk of distant spread, as would a nadir higher than 1, a rise that begins less than two years after treatment, and a doubling time of less than six months. 14