Spatially Fractionated Radiotherapy (SFRT), as characterized by its heterogeneous dose distribution within the tumor target, represents a novel approach in radiation therapy approach.
Our institution pioneered the use of GRID and LATTICE techniques within Hong Kong and the Greater Bay Area in the treatment of large, bulky and/or radioresistant tumors. These tumors confer poor prognoses, have limited treatment options and represent unmet treatment needs. Contrasting with the conventional external beam radiation therapy (EBRT), which typically involves uniform dose administration across the target treatment area, the GRID therapy employs a physical GRID block to create high-dose "spots" while sparing areas in between beamlets. Such heterogeneous dose delivery potentially enhances therapeutic effects and mitigates treatment toxicities. On the other hand, deep-seated tumors with surrounding critical organs-at-risk could be treated with the LATTICE technique using multi-leaf collimators and volumetric modulated arc technologies to allow better individualization and treatment adaptation.
While the exact radiobiologic mechanism of SFRT remains partially understood, its unique therapeutic profile was postulated through an initiation of radiation-induced bystander signaling, tumor microvasculature damage and immunomodulatory effects. This Masterclass outlines the origins and principles of SFRT, and discusses the potential underlying mechanism, treatment planning processes, and clinical application. We share our local experience with case highlights on the promising outcomes of SFRT demonstrating effective tumor regression and favorable toxicities in the treatment of challenging clinical scenarios. Further clinical research and standardized guidelines are warranted to refine novel strategies and expand access to innovative cancer treatment modalities.
