{"entity":{"id":"proton-arc-therapy","kind":"technology","name":"Proton arc therapy","aka":[],"tldr":"Rotating the proton beam continuously around the patient instead of firing from a few fixed angles, to spread the entrance dose and sharpen the target dose.","summary":"Proton arc spreads low-weight spots across a continuously rotating gantry, so each direction contributes only part of the dose, improving conformality and robustness to range uncertainty. Vendors have released treatment-planning implementations and first patients have been reported at a small number of centres; a September 2026 search of ClinicalTrials.gov found no randomised comparison against intensity-modulated proton therapy. Delivery time and quality assurance are the practical barriers.","status":"phase-1","asOf":"2026-09-08","links":[{"label":"ClinicalTrials.gov: proton arc therapy","url":"https://clinicaltrials.gov/search?term=proton%20arc%20therapy"}],"tags":["frontier"],"related":[],"cancers":[],"sections":["radiation"],"technologies":["proton-therapy","imrt-igrt","sbrt"],"targets":[],"drugs":[],"companies":["iba","varian","mevion"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":["intensity-modulated-proton-therapy"],"notes":[],"principle":"Spot-scanned protons are delivered during continuous gantry rotation, with energy layers distributed across angles so each direction contributes only part of the dose.","strengths":["Better normal-tissue sparing than fixed-field proton therapy in planning studies","More robust to setup and range error","Runs on existing proton hardware"],"limitations":["No comparative clinical outcome data","Long delivery and QA times","Adds planning complexity for uncertain benefit"]},"route":"/technologies/proton-arc-therapy/","neighbours":{"section":[{"id":"radiation","kind":"section","name":"Radiation Therapy","route":"/fronts/radiation/"}],"technology":[{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"intensity-modulated-proton-therapy","kind":"technology","name":"Pencil-beam scanning and intensity-modulated proton therapy","route":"/technologies/intensity-modulated-proton-therapy/"},{"id":"proton-therapy","kind":"technology","name":"Proton therapy","route":"/technologies/proton-therapy/"},{"id":"proton-therapy-systems","kind":"technology","name":"Proton therapy machines: cyclotrons, synchrotrons and single-room systems","route":"/technologies/proton-therapy-systems/"},{"id":"sbrt","kind":"technology","name":"SBRT / SABR (stereotactic radiotherapy)","route":"/technologies/sbrt/"}],"company":[{"id":"iba","kind":"company","name":"IBA (Ion Beam Applications)","route":"/companies/iba/"},{"id":"mevion","kind":"company","name":"Mevion Medical Systems","route":"/companies/mevion/"},{"id":"varian","kind":"company","name":"Varian (Siemens Healthineers)","route":"/companies/varian/"}],"roadmap":[{"id":"frontier-2035","kind":"roadmap","name":"Radical oncology: what could change the war by 2035","route":"/roadmaps/frontier-2035/"},{"id":"radiation-roadmap","kind":"roadmap","name":"Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH","route":"/roadmaps/radiation-roadmap/"}],"term":[{"id":"bragg-peak","kind":"term","name":"Bragg peak","route":"/terms/bragg-peak/"}]}}