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@heavyphil A great question regarding entry doses. I never got to ask those questions because I had already decided on the Adaptive Photon Approach. I'm not sure if technology is still the same, but I read a lot about Protons leaving "tan" marks on the sides of your hips where the entry dose enters. I asked about this with my Adaptive IMRT and was told that there would be no tanning or other skin irritations because the gantry moves around you and there is not any one particular spot subjected to damaging levels of radiation (except the target area in and around the prostate). I'm not sure of the mechanics of how protons is beamed into your body or whether newer gantry technology has corrected the higher entry dose issue (my perception & words only), I didn't get that far.
To me, any irritation or tanning indicates exposure to healthy cells: the opposite of my personal treatment goals. Similar to diarrhea from photon radiation, which to me indicates unwanted exposure to the rectum. To better protect my rectum I chose to use a Bioprotect spacer rather than SpaceOar or other gel. Recently approved, Bioprotect is a saline filled balloon that provides an additional 2-3 mm space over and above SpaceOar. I am now 18 days into my 28 day IMRT and have had zero rectal side effects. None.
Also relatively newly approved and studied, Adaptive Photon Therapy constantly monitors my prostate position as the treatment is being given. Most days the Linac stops as sudden internal gas might appear and until it dissipates, a few seconds. Or it stops so the rad techs can re-position me a millimeter or two as my bladder continues to fill while laying on the table during treatment and shifts the target field slightly. This gives me comfort that the treatment dose is going where it needs to be with minimal unnecessary exposure to normal cells.
For me, I am super pleased that my research and treatment goals have led me to the right treatment for me.
Replies to "@heavyphil A great question regarding entry doses. I never got to ask those questions because I..."
@jesse65 Yup, the Linac - even used with photons - is a great therapy; if the prostate leaves the target zone in 3D the machine automatically turns off, sparing delicate surrounding tissue.
Great for primary treatment, but not so much for SRT, even though it’s used for that as well.
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@jesse65 What you’ll find is that proton - as this graphic shows - is less likely than photons (x-rays) to cause skin irritation/tanning/burn/damage because proton doesn’t release the majority of its energy until it reaches a pre-determined depth. (This is called its Bragg-Peak characteristic.). Because of this, its initial energy at the skin can be lowered.
This has nothing to do with newer gantry technology; it’s a physical nature of protons that photons do not have.
This was a scientific discovery ( by William Bragg) when shooting protons through various substances, long before protons started being used for medical treatments.
Also, that adaptive technology you mention was first used with photon treatments well before it was incorporated into proton treatments. Each advancement builds on the previous one.
It’s great that your treatments are going well.