Hi, I’m Dr. Scholz. Let’s talk about prostate cancer.
In this video, we’re continuing our series of the PCRI staging guide. In particular,
we are covering the Teal stage otherwise known as intermediate risk prostate cancer. Teal
is a very broad base stage with some men who are in Low-Teal who can do active surveillance
and some men who are in High-Teal that need combination therapy. In today’s discussion
about proton therapy, we’re talking typically about giving proton therapy by itself, although
it can be used in combination hormones and seed implants, but this is done much less
commonly. For most men, proton therapy would be appropriate for someone who is in what
we call Basic-Teal—that would be sort of an intermediate, intermediate risk prostate
cancer. Other options are doing just a seed implant, or just IMRT, or just surgery, or
hormone therapy.
I think of proton therapy as being very similar to other forms of beam radiation such as intensity
modulated radiation therapy or IMRT which is sort of the standard for beam radiation
these days. Frankly everyone has heard the marketing pitch about proton therapy being
less toxic than IMRT because the radiation enters into the target, but unlike x-rays
doesn’t exit out of the backside of the body, so only half as much of the body is
exposed, and on paper that looks great and in practice it appears that IMPT or intensity
modulated proton therapy is certainly tolerable and the side-effects are no worse than IMRT.
Unfortunately, there are no definitive studies that have ever shown that intensity modulated
proton therapy is less toxic than intensity modulated radiation therapy; it is much more
expensive, there are relatively few centers that do it, but all-in-all in the practical
day-to-day decision making for prostate cancer therapy I tend to think of intensity modulated
proton therapy to be very similar if not identical to intensity modulation radiation therapy.
Now you may have not heard the terminology intensity modulated proton therapy and everyone
should be aware that older conformal proton therapy that started back in the 1990s is
still being done in some centers around the United States. It is decidedly inferior to
the modern computerized type of radiation that is available called intensity modulated
proton therapy and if I was going to undergo any type of beam radiation and if it happened
to be proton therapy, I would never use the older conformal type. I would only go with
the IMPT or intensity modulated proton therapy. Most of the new centers that are being built
deliver IMPT, not the old conformal type of proton therapy.
So if you just sort of change out IMPT for IMRT, you can go back and refer to our video
on IMRT for Teal (that we have already put online) and look at the pros and cons of IMRT
compared to things like seed implants and what not. The bottom line is that the beam
radiation doctors with IMRT or IMPT are unable technically to deliver the same dose that
can be delivered with a seed implant. So if it comes down to looking at some form of beam
radiation with some form of seed radiation, typically if you’re looking purely at cure
rates you’re going to get a higher cure rate with a seed implant than with intensely
modulated radiation or intensely modulated proton therapy. So why would you used IMPT
or IMRT in anyone if seed implants provide higher cure rates? Well if you look at Basic-Teal
which is just one step away from active surveillance, the Low-Teal patients, the cure rates are
going to be excellent with just about anything you do. So some men may prefer a non-invasive
form of radiation rather than seed implants which are invasive; it requires a procedure,
needles are stuck in, you get anesthesia, and all these sorts of things. So the beam
radiation is attractive because it’s non-invasive.
Now, both IMRT and IMPT historically have required daily visits (Monday through Friday)
for a short treatment over a nine-week period. This is changing rapidly and both IMRT and
IMPT (as of 2019) it appears can be safely given in five weeks which is far more convenient,
appears to be equally effective, and does not appear to have any additional side-effects
so five weeks rather than nine weeks of therapy is rapidly becoming the new standard time
period for IMRT and IMPT.
So I don’t have any really additional comments about IMPT as it compares to IMRT. It’s
a perfectly good form of treatment, just as IMRT is a perfectly good form of treatment.
If you happen to be situated geographically close to a proton center—because remember
you have to go there for five weeks—it’s perfectly reasonable to do IMPT for Basic-Teal
and consider it a form of combination for High-Teal although you’d be adding a seed
implant and some hormone therapy. Please see our video on Combination therapy for Teal
to get more details in that regard.
In summary, as a full-time prostate expert, I view IMPT interchangeable with IMRT. Whenever
you go for any form of treatment, you always want to go to a reputable center that has
a large volume of prostate cancer patients, a lot of experience and practice delivering
this type of treatment, but assuming that basic criterion is met IMPT is a perfectly
reasonable form of therapy. I do not recommend it as being advantageous over IMRT because
there is no scientific evidence, and in my own daily experience I have not seen any difference
in outcomes.