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Why intrafractional motion is important with SBRT

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Prostate Cancer
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Posted 7/10/2015 6:31 PM (GMT 0)
A recent study shows how toxicity can get way too high if intrafractional motion is not tracked during SBRT. There are a lot of other factors aside from dose that go into an optimal SBRT plan. Here's a good checklist for ROs to consider and patients to ask about:

The multi-factorial nature of SBRT safety

- Allen
Posted 7/13/2015 5:53 PM (GMT 0)
Someone in my support group asked about IMRT plans - either as primary therapy, with a brachy boost, or as salvage. Would they benefit from tracking intrafractional motion too? I think the benefit would be much smaller and there is a lot less risk to not having it. At only 1.8-2.0 Gy per treatment, a lot less damage is done by a single "miss." Tracking once at the start is probably adequate.

There are a couple of treatments - Tomotherapy and ViewRay - that track continuously, but it is questionable whether the CT in Tomotherapy, or the low power MRI in ViewRay have enough precision to keep the toxicity low enough for SBRT.
Posted 7/14/2015 2:30 AM (GMT 0)
Allen, this part about Baumann's high risk patients caught my eye:

"Bauman et al. treated 15 high-risk men who were either frail and elderly, or who refused a long course of IMRT. They were all given 12 months of ADT beginning 2 months before SBRT."

As you know I am a high risk patient of Dr. Chris King at UCLA and have had no adverse side effects since the final SBRT fraction on 10-20-2014.

Dr. King attibuted the low rectal dose on my Dose Volume Histogram to a perfect storm of favorable anatomy and visceral fat, the ony doctor who ever told me to not lose weight, at least not prior to SBRT treatment, when i aksed him if I had to lose weight to have the treatment.

Continuous self correcting based on the fiducials obviously did not hurt either.
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