Alright, Dr. Scholz. So our first question is what should a person's PSA be after radiation?
I know this is a common question—maybe it's different types of radiation. What should
it be?
So, there's a time component because radiation people mistakenly believe that it burns the
cancer out and so the PSA should go down because it killed the cancer. But, the problem is
that it doesn't work that way. What it does is it poisons the cancer cells and when they
decide to divide down the line, six, twelve months later, that's when they decide to die
and that's when the PSA goes down. So, the PSA slowly declines after radiation down to
about 0.5 over a 6 to 24 month period. It varies quite a bit from patient to patient.
Now, that, of course, is based on the idea that they're not getting some hormone treatment.
If people get hormone treatment with radiation as they often do, PSA will plummet to undetectable
levels usually within a couple of months. And then I've seen people get nervous about
rising PSA after radiation when they stop their hormone treatment. So, the PSA has been
less than 0.1 all the time of hormone therapy, and then hormone therapy stops testosterone
returns, and then the residual prostate gland will make a little bit of PSA and the PSA
may go up to 0.2, 0.3, 0.4 making everyone really nervous about the possibility of cancer,
but really it's just to be expected based on the fact that men that undergo radiation
still have a prostate and they're still making a little bit of PSA. So, short answer, the
PSA should probably be from 0.2-0.5 a year or two after the radiation. That would be
a normal PSA. That would be consistent with a complete remission.
Okay, and after radiation, how many times in what time frame should the patient get
the PSA checked? So, do they get it every three months, every six months to check that?
Mm-hmm, so usually we do it on the extending program. After the radiation therapy is completed,
we will check the PSA every three months for two years and then for the ensuing three years
out to five years we'll check it every six months and then once a year after that.
Okay. And after radiation and, you know, the PSA is continuing to decline and you may see
that bump, is there any imaging that the patient does within those year time frames?
Well, that's one of the really cool things about PSA is that if it's behaving the way
we want it to behave, you don't need imaging like you would with a lung cancer, colon cancer,
breast cancer. Prostate-specific antigen for prostate cancer is really accurate. The exception
is something you mentioned in passing, you mentioned the word "bump." PSA bump after
radiation is thought to be due to delayed radiation inflammation, we call it prostatitis.
The PSA bump phenomenon is more common in men that get fast radiation. So, more and
more men are doing something called SBRT (stereotactic body radiation) where they get the radiation
in two weeks, and for some reason, that equates with more delayed prostatitis which can occur
anywhere from one to four years after the radiation and cause a temporary rise in PSA—not
from cancer, from inflammation—and historically, we just had to sit on our hands and worry
and try to figure out what was going on. Now, with these new PSMA-PET scans, when men's
PSAs go above 1 or 2, we'll think about getting a PSMA PET scan and make sure there's no cancer.
But PSA bumps are common after SBRT; they're common after seed implants; they occasionally
will happen after proton therapy and IMRT as well. So, just because the PSA goes up
a little bit, don't jump off a bridge. It's time to evaluate what's going on, not just
assume that it's a cancer coming back.
And the common timeframe that you may see a PSA bump is within any timeframe a year
after or...?
Anywhere from immediately after the radiation out to three or four years after the radiation.
Gotcha. Thank you.
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