Dear OncoLink "Ask The Experts,"
How high can the PSA go? Is it a reflection of how much tumor is present?
Richard Whittington, MD, Associate Professor of Radiation Oncology at the University of Pennsylvania School of Medicine, responds:
It is possible for the PSA to go to very high levels. There is no absolute maximum value. In fact, I have seen PSA values over 2000 ng/mL. As a rule of thumb, the higher the serum PSA, the more extensive the tumor, but this is not an absolute rule or a direct relationship. It varies from individual to individual. For example, a man with a PSA of 40 ng/mL does not have twice as much tumor as a man with a PSA of 20 ng/mL. It IS generally true, however, that a man's PSA will go from 20 to 40 when the tumor roughly doubles in size. Each person's tumor makes and leaks PSA at its own rate. Similarly, I have patients with PSAs over 300, yet who are alive without tumor 10 years after receiving radiation and hormones. Having said that, a smaller fraction of that group is alive than out of the group of men with PSAs of 10.
Another factor is that other things can make PSA rise. The first two abnormal PSAs I saw were before the test was approved, and both patients had bad cases of gonorrhea. These men's PSAs were about 100. A bladder infection will make it go up by 4 to 10 points. An injury to the prostate will make it go up. I had one patient who was a long-distance cyclist who told me that his PSA could be elevated by a long bicycle ride. Ischemia (lack of blood flow to tissue) of the prostate can make it go up. It is thought that this may be the cause of the "PSA bounce" (PSA goes up, then back down) that is sometimes seen after radiation, as a result of local scarring caused by the radiation.
One other thing to keep in mind is that tumor that recurs after being treated with hormones generally tends to make less PSA than that same tumor before exposure to hormones. So in a man who has a PSA of 20 and goes on hormones, if the tumor becomes hormone-refractory, it may have the same tumor burden but with a PSA of only between 5 and 15.