AUTHOR=Mazal Alejandro , Vera Sanchez Juan Antonio , Sanchez-Parcerisa Daniel , Udias Jose Manuel , España Samuel , Sanchez-Tembleque Victor , Fraile Luis Mario , Bragado Paloma , Gutierrez-Uzquiza Alvaro , Gordillo Nuria , Garcia Gaston , Castro Novais Juan , Perez Moreno Juan Maria , Mayorga Ortiz Lina , Ilundain Idoate Amaia , Cremades Sendino Marta , Ares Carme , Miralbell Raymond , Schreuder Niek TITLE=Biological and Mechanical Synergies to Deal With Proton Therapy Pitfalls: Minibeams, FLASH, Arcs, and Gantryless Rooms JOURNAL=Frontiers in Oncology VOLUME=10 YEAR=2021 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.613669 DOI=10.3389/fonc.2020.613669 ISSN=2234-943X ABSTRACT=

Proton therapy has advantages and pitfalls comparing with photon therapy in radiation therapy. Among the limitations of protons in clinical practice we can selectively mention: uncertainties in range, lateral penumbra, deposition of higher LET outside the target, entrance dose, dose in the beam path, dose constraints in critical organs close to the target volume, organ movements and cost. In this review, we combine proposals under study to mitigate those pitfalls by using individually or in combination: (a) biological approaches of beam management in time (very high dose rate “FLASH” irradiations in the order of 100 Gy/s) and (b) modulation in space (a combination of mini-beams of millimetric extent), together with mechanical approaches such as (c) rotational techniques (optimized in partial arcs) and, in an effort to reduce cost, (d) gantry-less delivery systems. In some cases, these proposals are synergic (e.g., FLASH and minibeams), in others they are hardly compatible (mini-beam and rotation). Fixed lines have been used in pioneer centers, or for specific indications (ophthalmic, radiosurgery,…), they logically evolved to isocentric gantries. The present proposals to produce fixed lines are somewhat controversial. Rotational techniques, minibeams and FLASH in proton therapy are making their way, with an increasing degree of complexity in these three approaches, but with a high interest in the basic science and clinical communities. All of them must be proven in clinical applications.