You can use photons to radiate a small area or: 20 years later, radiate one area with protons. They recommend a mastectomy for me if my cancer comes back.

I only know that it’s supposed to be safer since it uses a different type of radiation & it’s more targeted to the specific area that it’s needed for. Please research any suggested treatments for your type of breast cancer. I’ve found it makes me feel like I’m less helpless, more in control, less stressed & more capable of deciding on what I think is best for “me”. Sometimes the “standard” treatments don’t feel like the best decisions for my specific situation but everybody’s case is different . I’ve found that every related treatment has pro’s & con’s. I’m picking & choosing what I’m willing to risk or not risk.
There’s lots of information on the web for Proton radiation & I’ve found not every facility has one. Here’s 2 links……Good luck & best wishes on your journey!
Here’s a link from the NCI.
https://www.cancer.gov/news-events/cancer-currents-blog/2020/proton-therapy-safety-versus-traditional-radiation
Another link this is for Susan G Komen
https://www.komen.org/breast-cancer/treatment/type/radiation-therapy/emerging-areas-radiation-therapy/

Once the proton radiation is calculated and administered, that's it. No more is needed.