Prostate cancer experts use PSA and PSMA tests in different ways in diagnosis and treatment. Dr. Heather Cheng from Seattle Cancer Care Alliance explains what PSA and PSMA measure and how the tests are used in prostate cancer care.
What’s the prostate-specific antigen?
Dr. Heather Cheng:
Yes, that’s a great question. So the prostate-specific antigen is basically a protein marker or something that is detected in the blood that is made by the prostate and can help us figure out if it’s too high, whether somebody might have prostate cancer actually. It can be useful to figure out who has prostate cancer, who doesn’t, but it’s more useful in helping when somebody has a prostate cancer diagnosis to help monitor what is going on with the disease, is the treatment working, is the treatment not working, and in that situation, it’s especially useful, it can be a little tricky, and the distinguishing between who has cancer, who doesn’t it kind of gets a B-, it’s the better than what we have, but it sort of is a little tricky.
Okay. So…what is prostate-specific membrane antigen?
Dr. Heather Cheng:
Yeah, so prostate-specific membrane antigen is similar to prostate-specific antigen, except for that it sits on the outside of cells that are prostate-related, or prostate cancer cells, or prostate, sometimes normal prostate cells, but it’s really useful now when people have had treatment for their prostate such as surgery to remove their prostate, but maybe their PSA or that prostate-specific member and antigen test and their blood is starting to go up, and that makes us concern that there is more cancer there, and so then we can do scans to see where is the…where in the body are the cells that express prostate-specific membrane antigen. So, kind of think about it as like a tag on the outside of the cell that says, “Hey, I’m kind of prostate-related, and so we can look in the body for cells that have that marker, the other reason it’s important is because we now have treatments that are targeted, they’re kind of smart bonds where they deliver radiation to cells that have that marker…that prostate-specific membrane antigen. So, it’s exciting for two reasons, one is to find out where the cancer might be, and the second is, if we know where it is, can we deliver treatment just to those areas and not to the healthy cells.