In my opinion it's a bit of a crap shoot as to whether or not your right lung will be damaged by radiation. You're heart is fairly safe since it's on the left side of your body. You most likely won't be required to hold your breath off and on during your radiation sessions since that is typically done for left side radiation because it shifts the location of your heart when your lungs are expanded with air. I'm sure it might help if the area to be radiated can be hanging down while lying on your stomach, but I've never heard of that technique before and it may not reach all the areas in your breast that require radiation to kill any remaining breast cancer cells. Maybe if your cancer was really close to the surface it could be an option. Ask your radiation oncologist and see what they have to say about it.

Some people do fine and have no immediate signs of lung or heart damage and others end up having issues. For me, I had chemo last year followed by radiation to the right side of my chest, armpit, and throat. My cancer was growing into the muscle by my chest wall and was in 16 of my armpit lymph nodes. I ended up with emphysema in my right lung and damage to my vocal cords from the radiation. I had 20 radiation sessions over a 4 week time period and my last 4 sessions had a high dose radiation boost. Sure, it sucks having these side effects, but it's better to me than having my aggressive stage 3c cancer spread to new areas so the risk and outcome are worth it in my opinion if it killed any remaining cancer cells. Even if you do go through radiation and have no immediate side effects radiation carries a risk for what is called "late effects" which are just like they sound, side effects that can show up anywhere from weeks, months, to years after you complete your radiation cycle.

My radiation oncologist gave me a bunch of literature to read about radiation and all the early and late side effects that can occur and what to expect while undergoing the actual radiation sessions. The information they provided was helpful and answered a lot of my questions. Talk to your doctor about your concerns and ask them to explain where/what will be radiated and how/why they are taking the approach they plan to use for your particular case. Good luck to you with your radiation ❤️

For me, they me hold my breath, which with an expanded lung, the breast is lifted away from the heart and lung. I have also heard of places having the patient lay prone, on the stomach with the breast hanging.
I had no problems from radiation.
Wishing you well!

Thank you very much for help.