How would you deliver whole breast radiotherapy in someone who cannot raise their ipsilateral arm above their head due to recent shoulder replacement surgery?  

Sometimes this comes up. If related to axillary surgery, I will often send to physical therapy/breast therapy and delay simulation for a few weeks. However, there are some cases where there is a preexisting shoulder issue. In these cases, I try to have arm akimbo and will consider VMAT whole breast ...

Would explore options of APBI, IMPORT LOW, and if not a candidate for above then whole breast with multi beam IMRT.

I should add that if comprehensive RT is needed, proton beams could be used safely with arm akimbo. A dosimetric comparison between the arm above the head and akimbo was done on 10 patients at MGH (Depauw et al., PMID 33458307). The results showed that the target structure coverage remained consiste...

Protons