This is all the rage lately. This is all the advertising in your field. Like I said, there's
so many different flavors of ice cream, but the flavor of the year, in my opinion, whenever
I travel—or I used to travel I'm not allowed to travel anymore—is SBRT, right? So this—one
form is Cyberknife, right? That's the type you talked about. They're advertising one week and
you're done; that's all you get. So now, can you explain to the audience how people watching can
go one week with radiation therapy five days in a row—or I know there's different sequences—and be
done with their treatment? Will you explain who's a good candidate for that?
Okay, so let me clarify one thing...
That's weird, you're correcting me.
No no no no no no, you know, so
when you — the more accurately you give radiation, the tighter you can make it. So,
think of this as the prostate, right? Think of my head as the prostate,? right?
Yeah, that's a scary prostate.
When I was a young man—I had hair I was a resident at Stanford—we
used to draw the radiation fields with a crayon.
We had a set of orthogonal images —AP and a lateral— and we would shoot contrast up the
urethra and put contrast in the rectum; we would take a CT slice—one slice—and we would run the
dose distribution on that one slice at the middle, and we would use either an 8x8 or a 9x9 field.
Okay but — and we, back in those days—not just at Stanford—everywhere
we assumed that the prostate did not move. Part of the reason why we assumed that was because we
didn't have anything we could do about it anyway so we might as well just assume it's still there,
you know? So, in about 1986 there was a guy from Michigan—I mean the Michigan people come in
handy every now and then—he was a physicist named Randy Ten Haken;
he wrote a paper and he showed that—guess what—the prostate position is moving around.
So — and then also, Michigan, they had the first FDA approved 3D planning system
called Scandiplan and the guy who was chair of the department happened to have trained at UCSF,
so as soon as he got this and got it approved, one of the first institutions to get it was UCSF. So,
I came to UCSF 30 years ago, 1990, and I arrived and they have a 3D planning
system and I had never seen one before; we didn't have them as a resident at Stanford.
And so at that time, you know, I could talk about how things evolved but the bottom line
is that people didn't understand 3D. They didn't understand those volume histograms. 3D evolved
to — I mean so conventional radiation which is what I was taught as a resident Stanford —
Yeah.
3D we helped pioneer; we were involved in the arc; the RTOG did the first studies in
the early 90s on a dose escalation using 3D; we then in the early 2000s, the NCI
sponsored something called the NCI IMRT working group. IMRT is intensity modulated radiation.
You use computers and leaves to modify the leaves so that — and then you use optimization
algorithms to limit the doses, and then we helped pioneer some of the work with image guidance. One
example of that was the first paper we wrote in 2006 or 2007 in post-op patients where we
took patients who had had radical prostatectomy, they were going to have radiation to cure them,
and we implanted gold seeds in the anastomosis where the prostate used to be...
Right.
...and we imaged that every day before treatment and we could adjust the beam to make sure that we
hit the right spot all the time. We also published probably I think it's the first paper I ever had
that was accepted with no modifications — we had we had three patients that had morbid obesity,
and we we put gold marker seeds in their prostate, and we showed that in people
that have morbid—the standard of care used to be to line people up on their tattoos...
Right.
... we showed that if you line people up in their tattoos who are morbidly obese,
you see you can move those tattoos wherever you wanted to, right?
Right.
You could completely miss the prostate. In other words, you bring the patient in, you put the
patient on the table, and you line up the beams, and you give the radiation and the prostate was
completely missed. That's not good because you don't cure the cancer and you radiate something
else, and that's bad. So, that's how image guided radiation got to be evolved is that guiding,
you know, that image guidance allowed us to make the fields tighter and tighter and tighter,
so when we went from conventional radiation to 3D conformal radiation,
to intensity modulated radiotherapy, to stereotactic body radiotherapy...
SBRT.
SBRT — when we use the Cyberknife, for example, it is tracking motion. So, you got seeds in there and
the beam is like, well, you know, if you move over here, we're gonna go over here; you go over there,
we're gonna move over there which you need to do if you're gonna treat somebody over 45 minutes
because air, and gas, and motion can occur. With a linear accelerator it doesn't track the same,
but the treatments given over a shorter period of time so it's sort of six in one hand half
a dozen in the other. If you do it — if it takes longer to deliver, you got to track it.
If you do it quickly, you just need to line it up make sure everything is set and hit it.