Abstract Body

Toward single dose radiotherapy: Dream or reality?

Radiation oncology has been entrenched and remains dependent on advancements in technology. The capability to safely generate high energy beam modalities, characterize beam time signatures, perform accurate dosimetry and deliver image-guided treatment plans has been the cornerstone of the field. Over the years, the ultimate success of radiotherapy has been reliant on interdisciplinary contributions from physics, chemistry and biology, but has moved forward conservatively, constrained by the very technologies that have now ushered in precision driven stereotactic approaches such as SBRT/SABR and SRS. However, ultra-high dose rate FLASH radiotherapy (FLASH-RT), overlooked for over 40 years, has now triggered a renaissance in the field, aimed at evaluating if/how dose rate modifications can be garnered for therapeutic gain. This so called “FLASH effect” has been defined and validated in vivo, and provides a heretofore unforeseen capability to minimize normal tissue complications while maintaining isoefficient tumor control. The potential promise of affording curative, dose escalation via FLASH-RT was immediately recognized, as dose limiting toxicities have and always will dictate the maximum tolerated dose that can be applied to any given tissue bed.

In this regard, photon and particle FLASH radiotherapy have the potential to transform healthcare, and dovetail nicely into current trends toward hypofractionation and possibly single dose therapy. This talk will highlight unpublished data regarding the response of the adult and juvenile rodent brain to fractionated FLASH-RT, and try to link the known and possible physico-chemical and biological mechanisms that might help us translate these findings to the clinic. If/how that laudable goal can be accelerated or even achieved through forthcoming advancements in FLASH-RT remains to be seen, but this intriguing technology has certainly captured the imagination of the radiation sciences and holds appeal at several levels, except perhaps for clinical profit margins.