Multicentre dosimetry audit in the European randomized phase III study of neoadjuvant chemoradiotherapy using proton versus photon radiotherapy in locally advanced oesophageal cancer

This study presents the results of a multicentre external dosimetry audit conducted as part of the PROTECT trial, involving nine European radiotherapy centres delivering proton and photon treatments. A dosimetry equipment vendor performed beam output audits at participating sites, verifying the absorbed dose-to-water measurements. Measurements used reference conditions based on the IAEA TRS-398, with ionization chambers traceable to primary standards. The audit compared local centre measurements to independent assessments, finding all within the acceptable 3% agreement threshold. The study is part of the successful implementation of a comprehensive, multicentre QA programme in the PROTECT trial.