So, Dr. Scholz, we have some questions regarding proton therapy from the comments section of our
YouTube channel. So, can we start off with what is proton therapy and how does it work?
Well, like any radiation, it's an invisible beam and the reason that these options have become more
palatable, attractive, successful in the last 10, 15, 20 years is the precise targeting that can be
accomplished now that wasn't really available in the past. When you give radiation, you want it to
go on the tumor or on the target and not spill over on the surrounding sensitive organs,
and there are a number of ways to do that now with these beam radiations. There's SBRT, proton
therapy, IMRT, and the proton therapy, really, has more similarities to photon therapy, which is the
SBRT & IMRT types of radiation, than people really want to acknowledge. Proton therapy has been
available in southern California where I've worked now for over 20 years and they're a lot more
similarities to photon radiation than differences. The proton people that administer this want to
set themselves apart. They're trying to market a somewhat more expensive type of radiation and
they must have an argument as to why you would pay more for proton therapy than for other types
of radiation, and the argument that they come up with is based on physics. The larger proton
as a compared to a photon particle tends to stop on the target rather than pass through the target,
the way photons do, and so the argument is that you only get half as much exposure to surrounding
tissue because the beam goes in and then more or less stops at the target instead of passing
through the other side of the body. It's a nice story, but I don't really observe, after being
in the southern California area now for 20 years and looking at photon therapy and proton therapy,
outcomes in patients— I don't really see that much difference, if any difference at all. The side
effects and the cure rates appear to be identical to quality photon therapy, quality IMRT or SBRT.
So, it's a perfectly good type of radiation; it is oftentimes more expensive, and I'm not
sure the expense is really justified, but there's certainly nothing wrong with it. I
would be much more concerned about the quality of the facility and the quality of the doctors
administering the radiation than I would be focusing on whether it's photon or proton.
If a patient was going to advocate to do focal proton,
what sort of criteria would they need to have?
Well, all focal therapy works best if you have a visible target; not all cancers are visible
on MRI, for example, and then it needs to be unilateral, so if you've got cancer on
both sides of the prostate then there's not a whole lot of argument for doing focal treatment,
but if you have— and then you meet a skillful qualified physician that can implement this
plan. If you have all three of those things, then I think it's worth a consideration because
although the studies haven't proven that the risk of erectile dysfunction is far
less with focal therapy, in my experience and what I've observed, it is indeed far less;
there's a much lower risk of erectile dysfunction with focal therapy as opposed
to treating the whole prostate. So, you mentioned that proton therapy has similar
side effect profiles to IMRT and SBRT. CAn you describe what those profiles are?
Yeah well, with well-performed modern radiation with any of those methodologies that you've
mentioned, the main concern these days is age-related risk of erectile dysfunction. So,
men that have whole prostate therapy that go into treatment at age 55—
well probably, about 25 percent of them will develop erectile dysfunction that does not
respond to Viagra or Cialis. If they're 65 it'll probably be closer to 40 percent,
and if they're 75 it'll probably be more like 60 percent of the men
will develop erectile dysfunction that does not respond to Cialis or Viagra.
As far as the side effects go, I know with certain forms of radiation that there are side effects
that could show up as much as two years later, is that the same with proton therapy as well?
Yes, delayed radiation side effects these days are much more rare. A lot of the side
effects that people talk about that would come either immediately or later were due to the
fact that the radiation therapy wasn't accurate enough to miss the bladder and miss the rectum.
Now, of course, we have SpaceOAR which pushes the rectum out of the radiation field. What's
left is the urethra going down the middle of the prostate which will get exposed to higher doses
of radiation and there's a couple percentage points risk of scarring, irritation, long-term
difficulties, that can happen with proton therapy or any of the beam radiations that we've been
talking about. There's a doctor at UCLA, Joanne Weidhaas, who's done some preliminary research
looking at the genetic profile of patients and they think with this test that they can
detect who the individuals are that are more likely to have that long-term urethral toxicity.
The risk is low already, but they can help even find those individuals and and suggest alternative
approaches. So, it's my understanding that proton came before IMRT, so that
leads me to think would the proton technology be outdated? Is there a newer technology that
people are doing in regards to proton therapy that would have better outcomes for patients?
Yeah, that's true. I mean proton therapy was a feasible form of radiation in my opinion before
photon therapy, IMRT, was developed. We had something prior to IMRT called 3d conformal
radiation, which was a slight improvement. All of this is about not getting spill over radiation,
and and the proton folks were very fastidious Loma Linda was an early utilizer of this in
trying to make sure that they didn't radiate so much of the rectum and the bladder, although,
their technology in my opinion doesn't match up to what we have today, which is a computer-targeted
intensity-modulated proton therapy which is available for example down in La Jolla
near San Diego, California. The older proton therapy available at Loma Linda
was providing decent outcomes— certainly superior to what was being done with photon therapy— this
is back in into the 1990s. These days, I think what's being utilized with that older technology
doesn't really measure up to what modern intensity-modulated proton therapy can accomplish,
and if people are shopping for proton therapy in this modern era,
I would look for intensity modulated proton therapy, not the older methodology.
I know that we have Carl Rossi in La Jolla. Do you know of any other
centers across the U.S. that are doing intensity modulated?
I believe a number of them are because they're here in southern California right in our backyard;
I'm not really familiar with the other centers, but Dr. Rossi was actually trained
at Loma Linda for a number of years before he switched over to the facility down near San Diego.
So, as a final thought for patients who are considering proton therapy:
I know that we always talk about it really matters who's doing the procedure,
and the questions that they could ask, you know, reading patient reviews online, looking at forums
of the doctors that they're considering, asking the doctors how many procedures that they've done.
Is there any other words of advice you would give to patients regarding this?
You know, it's who has had experience seeing how the patients have done. The things you mentioned
are probably the best for most people. If you have doctors that are referring to these centers,
the doctors will see over time how their patients do, and so you could talk to—
if there's urologists or family doctors that are referring patients to a certain center,
you can talk to them about the types of results they've been seeing in their patients.
So, we have a patient who is commenting on one of our videos,
and they were saying that their urologist told them that if they get radiation there's a
certain percentage chance that they could have secondary cancers down the line caused by the
radiation. Do you find this to be true? Well, I think it's going to be a far far less common,
and let me just say, historically, it's been very uncommon, but, yes,
rare cases of bladder cancers or rectal cancers from 10, 20 years ago do occur,
less than 1 percent of patients, so we screen patients that have had previous radiation for
these types of tumors after say 10 years out, but there's so little radiation now being
administered to the rectum or the bladder with modern radiation,
I would predict that down the line that the risk of secondary tumors is going to be negligible.
Thanks for watching. If you would like more information about prostate cancer
you can go ahead and subscribe to our YouTube; channel we come out with new
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we have tons of information on prostate cancer that will help you.
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