Published in JAMA, this is the results of the FAST-01 proton FLASH trial. This trial was set to test the clinical workflow feasibility, treatment related toxicities and pain relief of proton FLASH, using a single-transmission proton beam delivering 8 Gy in a single fraction at a dose rate ≥40 Gy/sec, for patients with bone metastases. 10 patients with 12 metastatic sites were irradiated and 8 patients were evaluated with a median follow up of 4.8 months. This study reported no FLASH-related technical issues or delays. The average time on the treatment couch was 18.9 (11-33) minutes per patient and 15.8 (11-22) minutes per treatment site. Pain relief was recorded in 67% patients including 50% a complete response (no pain). Adverse events were mild. This study concluded that treatment efficacy and toxicity profile were comparable to those of conventional radiotherapy, and proton FLASH was clinically feasible.