Any trials showing long term side effects of 20 day IMRT vs 38 day?

I had 20 sessions of IMRT w/o spacer as primary treatment to prostate last October (2025). Side effects were and are minimal so far. No urinary changes to speak of. Mild bowel urgency at times which I can control by watching what I eat.

My problem is the only time I watch what I eat is just before it enters my mouth. 🤣😯🤣

My understanding:

Kishan published a study in The Lancet this April https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(25)00034-8/abstract
UCLA put out a press release describing the work:

"A new large-scale study co-led by UCLA Health Jonsson Comprehensive Cancer Center investigators provides the strongest evidence yet that a shorter, standard-dose course radiation treatment is just as effective as conventional radiotherapy for prostate cancer, without compromising the safety of patients."
https://www.uclahealth.org/news/release/study-confirms-safety-and-efficacy-higher-dose-per-day
Keep in mind: for patients with localised prostate cancer.

For those who may still believe a shorter course of treatment must be more dangerous: The study distinguished between two types of shorter course treatment. Isodose MHFRT, and Dose-escalated MHFRT.

"Isodose MHFRT", apparently, means higher dose per treatment, less number of treatments compared to the formerly standard 38 days, less overall dose, but equivalent "biologically equivalent dose".

"Dose escalated MHFRT", apparently, means higher dose per treatment, less number of treatments compared to the formerly standard 38 or so days, less overall dose, but higher "biologically equivalent dose".

Biologically equivalent dose means a lower overall dose that is theoretically and observationally equivalent to the higher total doses formerly delivered over more sessions.

The study found that isodose MHFRT was as effective with no worse side effects. Dose escalated MHFRT had worse side effects.

The Kishan et.al. "Interpretation" of their study, as published in The Lancet:

"Isodose MHFRT and dose-escalated MHFRT both have similar efficacy compared with CFRT, but dose-escalated MHFRT is associated with higher physician-scored and patient-reported bowel toxicity. Isodose regimens, eg, 60 Gy in 20 fractions, should be the standard MHFRT regimen for localised prostate cancer."

Re: which machine?

The machine used for my recent 20 session RT was the Ethos Hypersight. It has cone beam CT imaging and a certain amount of ability to respond to daily changes observed by its superior imaging. It can, to a certain extent, tweak that days radiation plan. It has capabilities the operators in my case didn't use as well. I think it can also interrupt beam delivery when it detects too much movement of its target. Whatever it uses to aim and deliver the radiation is much smaller than some of the huge gantry things a lot of other machines have. It can change the direction the beam comes from very rapidly, which shortens the time a patient has to be motionless on the table.

I think Kishan is a big proponent of MRI-Linac.

The Prostox test sounds to me like it could be a big help for you to make a decision. Kishan was a major player in its development. Some patients develop more side effects with some RT treatments than others, and the test tries to predict what will happen.

@climateguy

I just want to add that Prostox predicts only urinary tract toxicity.

Also, everybody promotes what they do and have in their hospital ; ). If they have CT based machine they will tell you why CT is better and if they have MRI based machine they will tell you how it is so much better and not to mention new proton centers - well they will tell you that nothing is better than proton lol ; ).

IMHO- all those machines are good to the level of how good is the RO and his technician and their plan. All the rest is just "theory". Many results also depend of a patient's compliance with RT protocols and also some people are just more sensitive to radiation and will end up with more side effects. : (((

PS: Regarding study mentioned above, I think that less than 400 patients were treated so far in that way.

@surftohealth88

There is a difference between Cone beam CT and CT that I was unaware of until I first heard about it not long ago. It is not theoretical, it is a difference.

I paid most attention to what first rate clinicians who work at centers where they can treat with protons or photons say when it comes to which is best, i.e. protons or photons.

Eg: Fred Hutch advertises their proton treatment for prostate cancer very heavily especially on regional sports shows. But they also have a lot of photon machines. When I met with my RO there and brought up the subject of protons he said the prostate clinicians there think the ads are misleading. He tends to use photons for prostate cancer.

Dr Brian Davis at Mayo Rochester, where they also have protons and photons, did a presentation about his opinion, recorded on video, published not long ago. He summed up his view as to which is better for prostate cancer: "it's a wash". https://www.youtube.com/watch

MRI-Linac is a relatively new machine. So is the Ethos Hypersight I was treated with. I mentioned both because I considered MRI-Linac, but eventually went with whatever machine the RO I had come to trust and respect decided to use, which happened to be a relatively new machine, i.e. the Ethos Hypersight. My comment about the Ethos machine was based on my first hand experience of being treated with it.

My RO at Fox Chase Cancer Center gave me the option of 25 or 40 sessions of IMRT. She explained the 2gy per 40 days was safer than 3.2 gy per 25 days both totaling 80 gy. I Didn't have the barrier gel install, so I picked the safer route. Only issue I had was some urinary urgency during the end of my treatment and a few weeks afterwards. I choose a center of excellence that does a high volume RT figuring higher quality treatment. I believe I received it. 😀

I had 20 sessions. Zero effects during or after the completion.