Parenchymal lung changes on computed tomography after stereotactic radiotherapy using high dose rate flattening filter free beams

Flattening filter free (FFF) beams allow fast delivery of stereotactic radiotherapy. To evaluate biological effects of FFF in lung, we compared parenchymal changes after FFF and non-FFF stereotactic volumetric modulated arc therapy. Standardized multi-observer consensus evaluation of follow-up CT scans revealed no major differences between FFF and non-FFF.