{"entity":{"id":"proton-vs-imrt","kind":"pairing","name":"Caution: proton therapy vs IMRT","aka":[],"tldr":"Protons stop inside the tumour; modern X-ray beams (IMRT) still exit through healthy tissue. That physical difference only matters if it changes cure or late harm enough to justify the cost, which randomised adult trials have not settled.","summary":"IMRT and pencil-beam protons can both shape high dose around a target. Protons remove the exit dose and raise linear energy transfer at the Bragg peak; IMRT is cheaper, more widely available, and has a larger randomised evidence base. Adult comparisons are mixed: some oesophageal data favour protons on toxicity; prostate and breast trials (PARTIQoL, RADCOMP) are the tests of whether late-tissue alpha/beta plus variable RBE produce a real window. Paediatric cases and re-irradiation near critical organs remain the clearest established uses. Do not treat proton as automatically better than IMRT.","asOf":"2026-09-04","links":[{"label":"PARTIQoL (NCT01617161)","url":"https://clinicaltrials.gov/study/NCT01617161"},{"label":"RADCOMP (NCT02603341)","url":"https://clinicaltrials.gov/study/NCT02603341"}],"tags":["radiation-wave5"],"related":["idea-bio2-let-rbe-ab-selects-protons","idea-fund-proton-coverage-with-evidence"],"cancers":["prostate","breast-hr-positive","esophageal","nsclc","medulloblastoma","chordoma"],"sections":["radiation"],"technologies":["proton-therapy","imrt-igrt","intensity-modulated-proton-therapy","linear-quadratic-model"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["linear-energy-transfer","relative-biological-effectiveness","alpha-beta-ratio","bragg-peak"],"trials":["partiqol","radcomp"],"people":[],"bottlenecks":["b-surgery-radiation-innovation"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"a":"proton-therapy","b":"imrt-igrt","rationale":"No exit dose and a distal LET rise can spare a late-responding organ or, if the edge sits in that organ, harm it. Alpha/beta of tumour versus late tissue decides whether that physical difference is biologically large.","evidence":"Paediatric and skull-base use is established on integral-dose grounds. Adult randomised evidence is mixed and still accruing (PARTIQoL, RADCOMP, NRG oesophagus and lung).","pairingType":"caution"},"route":"/pairings/proton-vs-imrt/","neighbours":{"idea":[{"id":"idea-fund-proton-coverage-with-evidence","kind":"idea","name":"Pooled coverage-with-evidence for proton therapy across all centres","route":"/ideas/idea-fund-proton-coverage-with-evidence/"},{"id":"idea-bio2-let-rbe-ab-selects-protons","kind":"idea","name":"Use LET, RBE and alpha/beta to decide when protons beat IMRT","route":"/ideas/idea-bio2-let-rbe-ab-selects-protons/"}],"cancer":[{"id":"chordoma","kind":"cancer","name":"Chordoma","route":"/cancers/chordoma/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"medulloblastoma","kind":"cancer","name":"Medulloblastoma","route":"/cancers/medulloblastoma/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"},{"id":"esophageal","kind":"cancer","name":"Oesophageal cancer","route":"/cancers/esophageal/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"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":"linear-quadratic-model","kind":"technology","name":"The linear-quadratic model and fractionation","route":"/technologies/linear-quadratic-model/"}],"term":[{"id":"alpha-beta-ratio","kind":"term","name":"Alpha/beta ratio","route":"/terms/alpha-beta-ratio/"},{"id":"bragg-peak","kind":"term","name":"Bragg peak","route":"/terms/bragg-peak/"},{"id":"linear-energy-transfer","kind":"term","name":"Linear energy transfer (LET)","route":"/terms/linear-energy-transfer/"},{"id":"relative-biological-effectiveness","kind":"term","name":"Relative biological effectiveness (RBE)","route":"/terms/relative-biological-effectiveness/"}],"trial":[{"id":"partiqol","kind":"trial","name":"PARTIQoL","route":"/trials/partiqol/"},{"id":"radcomp","kind":"trial","name":"RADCOMP","route":"/trials/radcomp/"}],"bottleneck":[{"id":"b-surgery-radiation-innovation","kind":"bottleneck","name":"Surgery and radiotherapy cure most, get least","route":"/bottlenecks/b-surgery-radiation-innovation/"}]}}