I just attended at talk by a Radiation Oncologist talking about:
(a) Intensity-modulated radiation therapy (IMRT)
(b) Image Guided Radiation Therapy (IGRT)
(c) Stereotactic body radiation therapy (SBRT)
(d) Cyberknife (with is just one type of SBRT)
(e) Proton Therapy
What I came away from this was:
1. The main difference between current forms of IMRT and SBRT, is not so much the precision but that SBRT just uses fewer doses of higher radiation.
2. All of these forms of radiation treatment, even proton therapy are going Stereotactic, with proton therapy bringing up the rear. It just provides too much benefit not to do it.
3. If You Aren'tgetting your prostate tagged with surgical implantation of two metal markers, you aren't getting precision anything. The newest equipment comes with what are called "cone beam CTs" that track those two metal markers and automatically guide the machine to make sure the radiation is going where it is supposed to, and not going where it is not supposed to.
4. He mentioned some brands of this cone beam tracking equipment: Calypso, and Varian On-Board Imaging system.
Bottom line is: If you are not undergoing surgery to get your prostate implanted with these two metal markers prior to radiation treatment, you are likely getting treated with old generation equipment that is no where as precise as the new generation equipment and can't be as precise as new generation equipment.
If you are getting treated with old generation equipment, you need to stop and start asking questions. The accounting department with its amortization tables, shouldn't be the professionals determining what equipment is being used to treat you.
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cesanon
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Henry Ford hospital in Detroit supposedly has what is called pin point radiation. where the computer tracts the moving cancer and has a very fine ray. Is this what you found out?
I learned the greatest limiting factor isn't the precision of the beam, it is being able to know where to aim it. Those black tattoos are nice. But they don't compare with a beam that is constantly adjusting itself to track the very specific (and constantly moving location) of your prostate.
The tracked beam moves faster than your breathing and your bowel's tiny systolic movements, or shifting caused by your pulse. With the concurrent CT scanning, it sees where your prostate is every millisecond of the treatment.
I recently received IMRT at MD Anderson and had three gold fiducials implanted (ouch) in my prostate prior to RT. I had wondered why a neighbor who received RT local didn’t get those. Thanks for your summary.
While it's true that SBRT uses extreme hypofractionation, that is not the only difference. Because of the extreme hypofractionation, it is critical that there are no "misses" - even a small miss can undertreat the prostate and overtreat the bladder and rectum. While fiducial markers or Calypso is used in IMRT, they are used differently for SBRT. (There is another kind of linac, Tomotherapy, that uses waste X-rays to track position.)
SBRT (VMAT or CyberKnife) utilizes intra-fractional tracking (it tracks the position of the prostate throughout the treatment). CyberKnife uses a robotic point-and-shoot strategy, while VMAT sprays multiple beams in an arc. VMAT is faster, allowing for less organ motion, while CyberKnife is slower. They both use stereoscopic X-rays for intrafractional tracking. All modern X-ray treatments use fiducials or Calypso, but the non-SBRT types only use them at the start of each treatment (inter-fractional) with cone-beam CT. Protons often forgo them in favor of rectal balloons to stabilize the prostate because of the danger of shadows cast by beams from the fixed gantry.
It's important that SRT involves a very different set of considerations, and seldom uses fiducials. None of this applies to pelvic lymph node or other metastatic treatment.
I participate on another board where I am happy to take time to answer questions from people who need to have answers. I also write a couple of blogs where I sometimes review subjects, often about radiation - you may want to check those out.
In 2010 and age 62, I had the old fashioned standard EBRT which did have beams shaped to suit the shape of my PG to ensure enough RT got to PG. Pathways to PG were horizontal through hip joints and vertical through bladder and rectum. I had a total of 70Grey. Accuracy would not have been much better with stereotactic guided by implants because all Xray beams spread out out when they shine through a body, like shining a torch through muddy water.
I found EBRT maybe did little to kill my PG Pca cells which were inoperable, and I later found that for Gleason 9 patients like me the failure rate of this old fashioned treatment is 90%. maybe 50% for a Gleason 5.
I met a man who told me he had same EBRT and ADT for 2 years and it killed all his Pca - and this was 10years after his Dx. Sell sure, but his Gleason score was real low..... and he probably had a weak form of Pca; the killing ability of Pca is different amoung men. I was told I had the bad killer type.
70Grey is not much RT using X-rays, and each pathway to PG cops 17Grey, so cartilages suffer, and bowel / rectum cops enough to cause some damage, and bleeding in 2/3 of met for maybe 12 months at 1.5 years later.
In 2016 I had SBRT with Calypso for 31Grey more to to PG and 45Grey to two chest lymph nodes, and I have no clue whether this worked because I began Cosadex added to ADT before the extra "salvation RT" Docs did put in 3 "beacons" to PG which guided the SBRT as accurately as possible, but after getting home after staying in Melbourne for 5 weeks for all this I had bad radiation colitis for 2 months, but no bleeding. Hydrogel was used to stop damage to bowels, but they still copped a bashing from SBRT. And my PG was already radiation affected and when beacons were installed, I bled really badly for 2 days after and docs said "this is not supposed to happen" but these dopes should have seen it was inevitable, but it turned out I was first patient in Oz in 2016 to get salvation SBRT where EBRT had been the initial main treatment. To kill Pg cells with RT, maybe 150Grey is needed and then all nerves all are stuffed. To get that much RT to the PG without LU177 etc, best is BT, brachytherapy, with up to 100 radioactive pellets. But that has to be done as initial therapy. There's a risk of prostate urethra either becoming very constricted or ripping apart so you piss into your internal organ cavity, and you get real sick.
But in 2016, Lu177 and PsMa scans had only just begun, I was never told that would have been better. 70Grey RT makes blood vessels in PG very likely to bleed a lot if cut with anything, most certainly with a 4mm dia application needle for 3.5mm dia radio beacons.
So I doubt I got much benefit from the salvation SBRT. Cosadex suppression lasted 6 months, I then began Zytiga, it gave 8 months, then I had 5 chemo shots, Psa went from 12 to 50. Psa went down to 25 after stopping chemo. Then I began Lu177 last November, 4 x 8week cycles, now Psa is 0.57, going down. I did have some more extra EBRT to hip joint area, in which there were two pea sized mets, one in pelvis and one in femur.
I'm pain free now, but many men see their Psa go down then pop right back up again.
I have been told that for post-RP SRT, the use of implanted fiducials is pretty meaningless - though that doesn't mean they aren't still offered. Post-removal, there isn't exactly a lot to fix metal to, plus there is generally more movement down there, so that the benefit of the fiducials is open to question. Or at least, that's what I was told, by an RO who fits them when the prostate is in place but not post-RP. It made sense to me, and his staff were extremely careful in matching images/tattoos up before each shot, so I never experienced any bowel etc issues - but I guess it depends on the experience of the team, and how well you are able to replicate the bladder fullness etc.
A lot of stabilising connective.tissues are cut away when the prostate is removed. And for large prostates there is a release of the compressive force that has built up as the prostate has grown over the years - so although you aren’t exactly walking around with a prostate-shaped void, neither is it anywhere near the solid packed tissue situation you refer to. Things move around, and more so with varying bladder and bowel filling. Fiduciary markers can be placed on neighbouring organs but their reproducibility is not great for the sort of reasons just noted. And yes, targeting is still critically important - it just has to rely more on use of imaging and attempts to reproduce rectal and bladder fill conditions. In my limited experience, this is where you want a team of operators who are interested in a. Heavy and your health, rather than pumping patients through.
I almost laid down in the perfect position today, but most times it seems more like a tug-of-war between the techs trying to get me positioned correctly. Once they had to punch in a number on the local control panel after the CT scan in order to tweak the positioning by a slight shift of the table -- that meant that they didn't pay enough attention to the tattoo/laser alignment. Halfway through my weekday lunchdates with TOMO2. Probably about five months until T hopefully returns to normal.
Bladder fills to different degrees with urine = not solid and variable volume.
Rectum fills to different degrees with stool = semi-solid and variable volume.
Variable volumes will exert different forces on squishy tissue and change its shape.
Not trying to hit a fairly solid fixed volume like a prostate, but targeting a wide spread thickened surface area. Think of the former prostatic fossa as now being a flexible shell or thick partial balloon that takes on differing shapes dependent upon internal (bladder) and external (rectum) forces. Shape shifting is minimized by consistent bladder fill and rectum voiding. Real time tracking of a few fiducials won't help if the shape of the target changes. During my pelvic floor PT sessions, as much time was spent on getting a relaxed pelvic floor as was time spent on getting sphincter control improved through kegels. A relaxed pelvic floor creates a smooth unlumpy hammock for the remaining organs to snuggle comfortably into in fairly consistent unstressed positions.
Interesting - I hadn't heard the bit about getting the relaxed pelvic floor before.... how exactly do they propose that you do that??
As far as your earlier comment goes - I found the only way to achieve a consistent rectal volume was to use one of those little liquid suppository enemas a set time prior to driving to the appointment. And they measured bladder volume ultrasonically, allowing for real-time adjustment to within a range. It all seemed a bit much at the time, but no side effects, so I guess it worked.
I listened to the June 2019 patient conference that UCSF put on. It was outstanding. One take-away was the unambiguous statement that proton therapy is no better than other radiation treatments despite all the ads on the TV and radio. UCSF basically said don’t bother with protons.
Agreed. But if they are the same now, once they start adopting the same targeting and stereotactic approach of the others, I would expect them to pull ahead.
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