Is salvage SBRT an option for focal recurrence of PCa after prior proton therapy for intermediate-risk disease?

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 (Valle et al., PMID 33309278). I do not think that protons vs. photons as the initial modality is critical here. SBRT is one of several reasonable options. All have a higher risk of side effects than the initial treatment, and this is important for the patient to und...

I am not aware of any data indicating that prior proton therapy is a contraindication to reirradiation for a focal intraprostatic recurrence. I would approach this patient as I would a patient who has recurred after photon irradiation. I would get an MRI in addition to a PSMA PET to help define the target as best I can, and I would get a biopsy to confirm recurrence and try to re-establish a grade group. In my opinion, re-irradiation is all about protecting the bladder, rectum, and urethra from ...