@melissa1979 — Thanks for your information.
I believe all Breast MRIs are done face down, and so are the biopsies following the findings via MRI. However, as I understand it, Radiation treatments' "position" depends on a number of elements including the type and size of the cancer; involvement of nodes; type of surgery; etc..
In my case, I had a lumpectomy for a multi-focal cancer, with no nodes involvement, and reconstruction. I also told my Radiation Oncologist that I wouldn't consider radiation because of the potential damage of radiation to healthy tissue, particularly the heart and lungs. So I am "face down" (traditional radiation) on a 20-treatment plan. I sure hope the position does help!!