The Radiosurgery Society Working Groups on GRID, LATTICE, Microbeam, and FLASH Radiotherapies: 2022 - 2023 Advancements Symposium and Subsequent Progress Made

Purpose: Since the inaugural workshop "Understanding High-Dose, Ultra-High Dose Rate and Spatially Fractionated Radiotherapy." hosted by the NCI and sponsored by the Radiosurgery Society (RSS), growing collaborations and investigations have ensued among experts, practitioners, and researchers. The RSS GRID, Lattice, Microbeam & FLASH (GLMF) Working Groups were formed as a framework for these efforts and have focused on advancing the understanding of the biology, technical/physical parameters, trial design, and clinical practice of these new radiation therapy modalities.

Methods and materials: In view of the steadily increasing clinical interest in SFRT and FLASH, a full-day symposium entitled "Advancements in GRID, LATTICE, and FLASH Radiotherapy Symposium" was established in 2022 that immediately preceded the RSS scientific meeting. This well-attended symposium focused on clinical, technical, and physics approaches for SFRT, while closely examining relevant radiobiological underpinnings. Practical clinical trial development was a highlighted discussion. An additional section reviewed proton therapy and other particle-based techniques for the delivery of GRID and Lattice therapy. A treatment planning and delivery tutorial for GRID, Lattice, and proton GRID/Lattice was directed towards the real-world considerations for the development of new clinical GRID or LATTICE programs. An overall similar approach was applied to the discussion of FLASH. This report summarizes the content of the first GLMF Symposium and related work of the RSS GLMF Working Groups in the field of heterogeneous and ultra-high dose rate irradiation, over approximately 2 years.

Results: The GLMF Working Groups have continued to expand in membership and attendance, and several resultant trial concepts, research efforts, academic discussions, and peer-reviewed publications have followed as the number of institutions and practitioners utilizing SFRT and FLASH continues to grow.

Conclusions: The GLFM Working Groups and the RSS continue to demonstrate excellent progress in proliferating use of and improving understanding of SFRT and ultra-high dose rate radiotherapy techniques.