Top Line: Is FLASH-RT safe to use for treating bone metastases near thoracic organs?
The Study: FAST-01 was one of the first trials to explore FLASH-RT in humans, and it demonstrated the feasibility of proton FLASH-RT for treating bone metastases in the extremities. FAST-02 tested the concept in higher price real estate in the chest (ribs, scapulae, sternum). The trial included 10 patients with 1-3 painful non-spine bone metastases located in the thorax. They were treated with 8 Gy in 1 fraction using proton FLASH-RT with a dose rate of >40 Gy/s. Safety and efficacy were in line with what would be expected from standard photon radiation. Remember, these trials were designed to confirm the safety of FLASH rather than exploring the potential therapeutic gains of FLASH. Six of 10 patients had a complete pain response, 3 partial response, and 1 had stable pain. Pain flare was reported by 3 patients. There were minimal adverse effects with no grade 2 or higher acute or late events reported.
TBL: FAST-02 showed no new safety signals when using FLASH-RT to treat thoracic non-spine bone metastases. The results of both trials further support the relative safety and efficacy of using FLASH-RT to treat bone metastases in humans. | Daugherty, Radiother Oncol 2026
The Study: FAST-01 was one of the first trials to explore FLASH-RT in humans, and it demonstrated the feasibility of proton FLASH-RT for treating bone metastases in the extremities. FAST-02 tested the concept in higher price real estate in the chest (ribs, scapulae, sternum). The trial included 10 patients with 1-3 painful non-spine bone metastases located in the thorax. They were treated with 8 Gy in 1 fraction using proton FLASH-RT with a dose rate of >40 Gy/s. Safety and efficacy were in line with what would be expected from standard photon radiation. Remember, these trials were designed to confirm the safety of FLASH rather than exploring the potential therapeutic gains of FLASH. Six of 10 patients had a complete pain response, 3 partial response, and 1 had stable pain. Pain flare was reported by 3 patients. There were minimal adverse effects with no grade 2 or higher acute or late events reported.
TBL: FAST-02 showed no new safety signals when using FLASH-RT to treat thoracic non-spine bone metastases. The results of both trials further support the relative safety and efficacy of using FLASH-RT to treat bone metastases in humans. | Daugherty, Radiother Oncol 2026