Conditional sparing in FLASH radiotherapy: Conformal dosimetry and ALARA remain essential.

Abstract

FLASH radiotherapy shows promise in reducing normal tissue toxicity while maintaining tumor control. However, preclinical and early clinical evidence reveal biological and technical uncertainties. We review preclinical and veterinary studies, highlight unexpected toxicities, and argue that the fundamental principles of precision and safety in radiotherapy-particularly conformal treatment and ALARA-remain crucial.