Abstract Body

Translation of FLASH radiotherapy from the lab to the clinic requires multiple advancements. Characterization of the physical parameters of FLASH such as dose threshold and dose rate must be accompanied by technical advances including devices capable of delivering and accurately measuring these high dose rates. In 2020, these requirements had been sufficiently met to allow first translation of FLASH from the lab to the clinic. As a first foray into the clinical application of FLASH, we designed a clinical trial using proton FLASH to treat metastatic carcinomas involving bones of the extremities. This choice was made for several reasons. Cyclotrons possess the inherent ability (with modifications) to produce FLASH dose rate radiation capable of treating tumors inside the body. Treatment of bone metastases with conventional radiotherapy uses dose prescriptions that fall into the range of parameters that are necessary for the FLASH effect determined in the laboratory setting. Restricting treatment to extremity metastases limits the risk of adverse events in the study population. In support of the clinical trial, in a clinical setting, a pencil-beam scanning FLASH-enabled proton therapy system was specially commissioned to deliver pre-defined rectangular fields at 8Gy-RBE at FLASH dose rates. The ensuing commissioning, treatment planning, metrology and quality assurance and radiation safety programs were evaluated and accepted using standard codes of practice for conventional proton therapy, where appropriate. This trial recently closed after accrual goals were met, and results from this will lay the foundation for subsequent trials investigating FLASH for more relevant clinical problems.

Abstract Body

Translation of FLASH radiotherapy from the lab to the clinic requires multiple advancements. Characterization of the physical parameters of FLASH such as dose threshold and dose rate must be accompanied by technical advances including devices capable of delivering and accurately measuring these high dose rates. In 2020, these requirements had been sufficiently met to allow first translation of FLASH from the lab to the clinic. As a first foray into the clinical application of FLASH, we designed a clinical trial using proton FLASH to treat metastatic carcinomas involving bones of the extremities. This choice was made for several reasons. Cyclotrons possess the inherent ability (with modifications) to produce FLASH dose rate radiation capable of treating tumors inside the body. Treatment of bone metastases with conventional radiotherapy uses dose prescriptions that fall into the range of parameters that are necessary for the FLASH effect determined in the laboratory setting. Restricting treatment to extremity metastases limits the risk of adverse events in the study population. In support of the clinical trial, in a clinical setting, a pencil-beam scanning FLASH-enabled proton therapy system was specially commissioned to deliver pre-defined rectangular fields at 8Gy-RBE at FLASH dose rates. The ensuing commissioning, treatment planning, metrology and quality assurance and radiation safety programs were evaluated and accepted using standard codes of practice for conventional proton therapy, where appropriate. This trial recently closed after accrual goals were met, and results from this will lay the foundation for subsequent trials investigating FLASH for more relevant clinical problems.