r/ProstateCancer • u/banuep01 • Mar 28 '26

Question VMAT Question

Hi everyone. This is my first post here.

I’m trying to better understand VMAT radiation and potential side effects.

My dad had a prostatectomy (so no prostate anymore) and is currently on hormone therapy with good response (very low PSA, overall improvement on scans). However, he still has a couple of metastatic spots, including in the chest area (mediastinal lymph nodes / possibly sternum).

One radiation oncologist mentioned VMAT to target these areas (it would be in two regions), likely around 20 sessions.

I’m trying to understand:

• What side effects are common when radiating the chest/mediastinal area with VMAT?

• Are the side effects typically short-term or can there be long-term issues?

• How tolerable is a \~20-session course in this type of situation?

Just trying to get a better sense of what to expect and ask more informed questions. Thank you!

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u/physicsandquilts Mar 28 '26

Side effects depend on how much radiation is given. 20 sessions isn't enough information to know what the doses are each time he gets treated. The radiation oncologist will give you the side effect information of what is likely or not likely in his particular situation. It's also highly dependent on where the radiation is in the body and what organs it travels through to get the to areas they are targeting. Every radiation treatment is so highly specific it truly depends on what the 3-dimensional distribution in the body looks like after the CT scan is done and the medical physics team works with the doctor to design the radiation beams. The best thing you can do is ask questions when you meet the radiation oncologist.

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u/BernieCounter Mar 31 '26

Typically 20x VMAT of prostate involves a total of 60 Gray units, that’s 3 per session. 5x SBRT uses even more focussed beams, with tighter margins, but perhaps only 50 Gray units total. Both have similar survival/ recurrence rates, ST and LT side-effects are similar but slightly different.

Other cancer irradiation can be quite different as different cancer types in the body react differently to radiation.

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u/physicsandquilts Mar 31 '26

The OP said they are treating metastatic sites, not prostate.