Advancements in GRID/Lattice, Microbeam and FLASH Radiotherapy

Abstract
Spatially fractionated radiation therapy (SFRT), the treatment of tumors with intentionally non-uniform dose distributions, is an area of rapid advance and high interest in radiation oncology, tumor biology and immunology.  Clinical experience in SFRT, that suggests high response and at the same time lower than expected treatment toxicity in the treatment of bulky, advanced tumors, continues to accumulate.  In parallel a growing body of experimental data postulates that the inherent dose heterogeneity of SFRT promotes bystander and abscopal effects as potential underlying mechanisms for higher tumor response.  Meanwhile, SFRT technologies and treatment techniques are continuously evolving.  Advanced multi-leaf collimation and volumetric modulated arc technologies have since broadened the original well-established GRID therapy capabilities. 

Clinically the SFRT concept has advanced from the initial treatment of palliative tumors to curative-intent therapy in bulky advanced primary tumors, and disease-specific pilot studies have shown promising tumor control and toxicity outcomes. 

However, multi-institutional clinical trials of SFRT are urgently needed.  In addition the wide array of SFRT technologies and the novel heterogeneous and-high dose prescription parameters, a profound departure from the current radiation oncology physics concepts, pose challenges. 

This session will review the current status of SFRT, an overview of clinical data, pertinent SFRT technologies, and potential biological underpinnings.  Clinical trial strategies, obstacles and pitfalls, and future directions will be discussed.  Novel concepts and early clinical data of ultra-high dose rate Microbeam and FLASH therapy will be reviewed.