Not quite as effective as Brachy Boost Therapy, but less toxic and more convenient.
Edit 1/26/21 - I heard a rumor that Canada may be starting a randomized clinical trial this year called ASCENDE-SBRT. ASCENDE-RT was the trial that proved that brachy boost therapy was vastly superior to EBRT-only in high and intermediate risk men, although urinary toxicity was also higher:
I think the new trial would randomize men to either:
(A) Brachy boost therapy: ADT+46 Gy/28 fractions of whole-pelvic IMRT + 115 Gy of I125 seeds in the prostate, or
(B) SBRT only: ADT+ 25 Gy/5 fractions of whole pelvic SBRT +additional 15 Gy/5 fractions to the prostate
Of course, it will be many years before we have any results.