Hi, I’m Dr. Scholz. Let’s talk about prostate cancer.
This video is about stereotactic body radiation therapy (SBRT). Radiation therapy when it’s
delivered by a beam involves going to a specialized facility, sitting in front of a machine for
a brief period of time on a daily basis (Monday through Friday) for a period of one or more
weeks. Traditionally radiation therapy required anywhere between 5-9 weeks of therapy. SBRT
is different because by giving larger doses on a daily basis, the treatment can be completed
within a week or two—maybe 3-5 visits to the radiation therapy facility. This is certainly
a lot more convenient. Radiation therapy has progressed most rapidly
in the area of beam radiation. If you’ve done even a little bit of research you are
probably aware of IMRT (intensity modulated radiation therapy) and IMPT (intensity modulated
proton therapy). SBRT is beam radiation but packaged over a much shorter period of time.
This type of radiation has been under investigation for about 10 years, and there has been concerns
about the delivery of such high doses over short periods of time. It does appear that
the cure rates are equal and it’s certainly a more convenient approach. The real question
is whether the side-effects would be worse. With the beam radiation the concerns for serious
side-effects consist of erectile dysfunction--which no one really believes is any different between
SBRT, IMRT, or IMPT. Because the rectal wall is very close to the posterior portion of
the prostate, the possibility of a long-term non-healing burn to the rectal wall has been
a concern, and some of the early studies suggested that the incidence of rectal burns called
“Proctitis” is a little bit higher with SBRT. This has been one of the reasons that
I had hesitated to use SBRT because if that side effect occurs it’s a real disaster.
Whether or not that’s the case, there’s a new type of technology out now called SpaceOAR.
SpaceOAR is a treatment that involves injecting a gel between the rectal wall and the prostate,
spreading the two apart so that the rectal wall no longer needs to be radiated in the
course of a normal radiation program. With the advent of SpaceOar, it appears there’s
no reason for concern that SBRT would be more toxic. Therefore, it compares favorably with
IMRT and IMPT. Apparently, it has similar cure rates, it’s clearly more convenient,
and if there are no additional side-effects it may be the best way to go.
So does this mean that SBRT (or CyberKnife) is going to completely replace proton therapy
and IMRT? Well there are a few areas where it certainly could, and one area looks particularly
attractive and that would be the possibility of doing more focal treatment. Many patients
are unaware that standard radiation (SBRT, IMRT, IMPT) involves targeting the prostate
gland--not the tumor within. The borders of the gland are the borders of the radiation.
Someday, especially now that imaging is improving so much we may be able to radiate the tumor
itself and spare much of the prostate. This could further reduce the potential for side-effects.
So SBRT might shine in that department, but radiation therapy via a beam delivery is used
commonly also to treat lymph nodes in the pelvic region and there’s little of any
experience now with using short courses like SBRT to accomplish that. The other thing that
is not quite clear is whether SBRT should be combined with seed implant radiation as
IMRT is, or whether it can be used instead of seed implantation therapy. So there’s
a lot of unanswered questioned still, but for the Teal patient (those that have intermediate
risk prostate cancer) SBRT in expert hands with the use of a SpaceOAR appears to be a
very attractive alternative for curative therapy for prostate cancer.