Is salvage SBRT an option for focal recurrence of PCa after prior proton therapy for intermediate risk disease? What volumes would you treat, and what dose do you recommend?

Yes, it is an option. There is a great need for randomized trials in the setting of local-only recurrence after definitive RT, and we do not know the optimal approach. The MASTER systematic review and meta-analysis is a good summary (PMID: 33309278). I do not think protons vs. photons as the initial...