All plans, both gantry and gantry-less, delivered radiation while maintaining dose to healthy tissue below the prescribed limit. Most gantry-less plans had similar target HI and mean OAR dose as gantry-based ones. Some gantry-based plans showed slightly better target coverage and were better at sparing healthy organs. For one patient, both plans were equally robust with respect to range uncertainties and setup errors, according to the researchers.

Only a very small percentage of cancer patients who are eligible for proton therapy receive it due to the high costs that come with building a proton therapy facility, as well as the distances required to travel to them, among other factors. According to the Particle Therapy Co-Operative Group (PTCOG), only 122 proton therapy centers in 20 countries were operational as of January 2022.


The findings, according to Yan, indicate that a modern PBS system could enable high-quality proton treatment in brain and head-and-neck cancer patients without non-coplanar beams and that with appropriate positioning and immobilization, no gantries. This would enable faster building of operational proton therapy systems at lower costs for providers and in turn, more affordable treatments for patients.

The findings were published in Medical Physics.

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