SBRT or Cyberknife 5 fractions

When comparing MRI-guided linear accelerators to CyberKnife for radiation therapy, the choice depends on clinical context, tumor characteristics, and institutional capabilities. Both technologies achieve sub-millimeter accuracy, but they differ in key areas:

CyberKnife excels at sparing nearby critical structures by creating steep dose gradients, particularly in complex cases like cardiac or prostate treatments. Its robotic arm allows non-isocentric beam angles for precise targeting of small lesions.

Linac-based systems (including MRI Linac) show advantages in reducing high-dose spillage to distant tissues and achieving faster treatment times. MRI Linac adds real-time soft-tissue visualization, enabling adaptive replanning during sessions.

For prostate SBRT, studies show no significant outcome differences between CyberKnife and Linac-based approaches. CyberKnife demonstrates slightly better organ-at-risk sparing, while Linac platforms offer comparable target coverage with shorter delivery times

Hard to pick one as better than the other.

thanks Jeff. that's very good info comparing the two.
do you have a comment on the radiation nurse's comment about not using adaptive radiation?

@erbill
I had 5 treatments with the Mridian MRI linac radiation machine but these days the Elekta Unity, with similar real time MRI features, is also available. Although Cyberknife, as I understand it, uses multiple beams automatically coordinated to radiate a small spot, I narrowed my choice down to Proton or Viewray's Mridian. I then spoke with 5 radiation oncologists trained or at centers of excellence, with direct experience with the machine, as well as the President of Viewray, at the time, for some additional insight. My goal was obviously, minimize the chance of a biological re-occurrence but also to reduce or eliminate side effects and toxicity for a better quality of life.

The dynamic adaptive capability was an important piece for me after the built in MRI which uses smaller margins (2 mm vs 3-5 for other forms of radiation) and the auto gating shutoff feature. Even though the prostate does not move as much as other organs, I wanted those capabilities as I knew the prostate could move because of bladder filling, rectal gas, or patient movement so I wanted it as part of the machine, just in case.

The bottom line for me was the built in MRI and smaller margins of 2 mm and full use of the machines functionality was best for my treatment.

The first link below is to an article from urology times talking about the Mirage randomized trial and its conclusion that there is a significant difference in toxicity and side effects between built in MRI vs fused CT or other images use. The second link is to another study showing support for the Mirage trial but over a two year period after the Mirage trial.
https://www.urologytimes.com/view/mirage-trial-margin-reduction-with-mri-guided-sbrt-reduces-toxicity-vs-ct-guided-sbrt
https://www.europeanurology.com/article/S0302-2838(24)02688-5/fulltext

...pcri.org. You-Tube video with Mack Roach MD UCSF radiation oncologist describes problems with the MIRAGE study showing better outcomes for the MRI 'guided' approach. (Ten days ago, end of April 2025)

fast forward to 15.00 to 24.00 minutes but it is all interesting
https://video.search.yahoo.com/yhs/search?fr=yhs-avast-securebrowser&ei=UTF-8&hsimp=yhs-securebrowser&hspart=avast&param1=n&param2=20241208&param3=Avast+Secure+Browser%7C122.0.24368.130&param4=17%7C5.2.590%7C&p=PCRI.org+video+of+Matt+Roach+MD&type=6320#id=3&vid=2879f8c46909fbb3e1c52861b38f39cb&action=click

@erbill
I had 5 treatments with the Mridian MRI linac radiation machine but these days the Elekta Unity, with similar real time MRI features, is also available. Although Cyberknife, as I understand it, uses multiple beams automatically coordinated to radiate a small spot, I narrowed my choice down to Proton or Viewray's Mridian. I then spoke with 5 radiation oncologists trained or at centers of excellence, with direct experience with the machine, as well as the President of Viewray, at the time, for some additional insight. My goal was obviously, minimize the chance of a biological re-occurrence but also to reduce or eliminate side effects and toxicity for a better quality of life.

The dynamic adaptive capability was an important piece for me after the built in MRI which uses smaller margins (2 mm vs 3-5 for other forms of radiation) and the auto gating shutoff feature. Even though the prostate does not move as much as other organs, I wanted those capabilities as I knew the prostate could move because of bladder filling, rectal gas, or patient movement so I wanted it as part of the machine, just in case.

The bottom line for me was the built in MRI and smaller margins of 2 mm and full use of the machines functionality was best for my treatment.

The first link below is to an article from urology times talking about the Mirage randomized trial and its conclusion that there is a significant difference in toxicity and side effects between built in MRI vs fused CT or other images use. The second link is to another study showing support for the Mirage trial but over a two year period after the Mirage trial.
https://www.urologytimes.com/view/mirage-trial-margin-reduction-with-mri-guided-sbrt-reduces-toxicity-vs-ct-guided-sbrt
https://www.europeanurology.com/article/S0302-2838(24)02688-5/fulltext

Thanks for your opinion.
I am leaning towards the mri guided sbrt over cyberknife due to the mri function. It appears that the cancer center I go to is not doing adaptive radiology with each fraction. I have been in contact with a patient on another site who had to convince the RO at this site to use the mri linac daily for his prostate cancer. I asked AI to prepare a list of mri linac sites. I would have to validate each site listed prior to posting. Looks like I would have to travel out of florida to get mri guided. There are cyberknife experts in my area though that have done cyberknife for PC for 20 and 30 years.