SBRT Late Stage Radiation Toxicity-Anyone Experienced These?

Late GU Toxicity at 31.9% doesn't jive with what is reported on this board nor my own personal experience.

Also worth noting that pin-point accuracy isn't *always* the best thing. Even MRI or PSMA PET can't find very small tumours (much less individual cancer cells), and a biopsy is just a sampling, so if the radiation affects too precise an area, but might miss something that matters.

Different kinds of prostate cancer have different risks of growing and spreading, and that will have influenced the radiation oncologist's recommendation. But in certain cases it's a actually good thing for the radiation to spread beyond the prostate so that it can pick up local spread (detected or undetected) in the surrounding area. It's a complicated balancing act between getting all the (significant) cancer and limiting the risk of side-effects.

I agree. I just read the study since I was unfamiliar with it, and if anything, SBRT was fractionally better than IMRT in this respect.
The purpose of the study was to ascertain if SBRT was “not inferior” to conventional radiation and the conclusion was that it WAS NOT inferior. They might both have SE’s but not one greater than the other.
Do agree, however, that MRI guided SBRT is better in many ways.

We are the living studies. 3 weeks post 25 rad sessions and still occasionally having to do the Pinguin hustle to the BR. Imodium if I have to go out for insurance.

@gsd Are you having MONOTHERAPY SBRT ?

You could take the PROSTOX Ultra test to predict whether you have an increased risk of late GU toxicity from SBRT.
https://mirakind.org/prostox-testing/
https://miradx.com/prostox

@clandeboye1, first thanks for following up! I'll remind you I'm a Gleason 3/4 with < 10% on one core diagnosed as 4. I had 6 cores of 3/3 out of 13 in an mpMRI-guided biopsy. My decipher score was low (.18).

This is a long-winded response to my treatment decision inquiries. Monotherapy RT is my plan. My read of the literature at this juncture is that Proton therapy hasn't realized its potential of reduced toxicity because there isn't the technology to gate the beam delivery to account for intra-fractional prostate movement. Intra-fractional movement of the prostate exceeds 3 mm in approximately 70% of the fractionated sessions, according to one study. That, in my opinion, partially accounts for the increased toxicity of OARs in both proton and photon EBRT. MRIs don't play well with proton beams and tend to distort the beams. As far as I can tell, ultra-fast CTs are just beginning to be paired with Proton, are very expensive, and seem to be reserved for other treatments than prostate (lung, pancreatic cancer, and spinal cord). I think Mayo Rochester has one, but it did not seem to be available to me when I inquired about it for treatment of prostate cancer. Two commercially available photon units with MRI gating technology are available: MRIdian and Electra. Electra has larger margins 3-5 mm, which I'm not sure offers a sizable advantage. I'm also not sure what is happening with MRIdian. Mayo doesn't use them. The two nearest locations to me in Kansas City stopped using them. So if anyone has any information on the current status of MRIdian and the reasons that some institutions have stopped using them, post links for more discovery or how to find the current operating locations of MRIdian capable facilities.

Thanks as always for your support and guidance!

@gsd I have reviewed the diffferent machines , with my Oncologist , using MRI and CT Guided technologies .
Clearly the MRI is the way to go , and insist on a rectum spacer . Many Oncologists insist they are not required . I err on the consertative side . The MR Linac guided ultra -Hypofractionated model machine is less available than the CyberKnife Machine . However " BOTH " can perform 2mm margin results .

@psychometric, your suggestion is right on! MiraDX PROSTOX tests are another step forward in trying to identify variables that might help PCa patients weigh their treatment options.
I did take the opportunity to take both Prostox tests, (Ultra- for 5 to 7 fraction SBRT and CFRT- for 35-45 fraction Tx). My results were low-intermediate genetic risk (2 on a scale of 5) for late grade 2+ GU Toxicity for both forms of EBRT. As you know, it's MiraDX's hypothesis that there is a subset of patients that are genetically predisposed to radiation toxicities and they may account for a significant portion of grade 3 or higher radiation toxicity side effects. It is still very early in their modeling and data collection. If my memory serves, the sensitivity of their SBRT Test was 65%, meaning that it correctly identified patients that experienced late grade 2 or higher GU toxicity reactions about 2/3's of the time. The specificity of their SBRT Test was better at 79%, meaning that patients like you and I that score low, have about a 4 in 5 chance they won't develop late grade 2 or higher GU toxicity.
2 cautions for others reading this:
- I am a PCa patient sorting through clinical studies to make my own treatment decisions. I am not a doctor.
- It is very early in the Prostox modeling and development. I believe the Prostox Tests shows promise, but MiraDX may have several hundred or a couple thousand data points. Decipher, as a comparison, has over 200,000 whole-transcriptome profiles from patients . For my part, I took the test to see if I was a 'high risk radiation patient' for either SBRT or CFRT. According to MiraDX, a patient can be high risk for SBRT but not for CFRT, or visa-versa. Since I wasn't high risk for either, in my mind both are in play for me.

@psychometric, keep us up to date on what you find out from MD Anderson. I am corresponding with a friend that just started Proton EBRT for PCa there this week.

Best wishes!

MRIdian system was built by ViewRay, which went bankrupt. I believe Elekta may have purchased what was left. @bens1 knows a lot about this subject so hopefully he’ll chime in.