External beam radiotherapy with electrons of low (IOeRT) and high (VHEE) energies: Status and prospects for conventional and FLASH irradiations

The field of cancer treatment is continuously evolving with the goal of enhancing tumor control probability, minimizing complications in normal tissues, and improving the life expectancy and quality of life for patients. Currently, there is a renewed focus on both low (Intra Operative electron Radio Therapy applications) and Very-High Energy Electron (VHEE) beams, particularly due to their potential to be delivered at FLASH intensities. The unique characteristics of electron interactions with matter can be leveraged to offer effective alternatives to standard Radiotherapy (RT) and Proton Therapy (PT) treatments, with electron technology being the most adaptable for FLASH treatment deliveries among the three. In this study, we explore the achievable efficiency in IOeRT and VHEE treatments at both conventional and FLASH regimes using a GPU-based fast Monte Carlo (MC) simulation as a tool for dose calculation and treatment optimization. The results obtained for partial breast irradiations and the treatment of pancreatic cancer will be compared with the latest technologies in RT and PT.