UK photon radiotherapy practice for Oligodendroglioma –data from the APPROACH trial (ISRCTN:1339049) radiotherapy quality assurance (RTQA) programme

Golten, Jennifer, Bruce, Anna, Egleston, Daniel, Miles, Elizabeth, Powell, James and Murray, Louise 2026. UK photon radiotherapy practice for Oligodendroglioma –data from the APPROACH trial (ISRCTN:1339049) radiotherapy quality assurance (RTQA) programme. Clinical Oncology , p. 104311. 10.1016/j.clon.2026.104311

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Abstract

Background: The APPROACH (Analysis of Proton vs Photon Radiotherapy in Oligodendroglioma and Assessment of Cognitive Health) trial is a UK randomised controlled study comparing photon RT with proton beam therapy (PBT) for oligodendroglioma, with a primary endpoint of neurocognitive function at five years. As part of the trial’s radiotherapy quality assurance (RTQA) programme, a national pre-accrual facility questionnaire (FQ) was undertaken to evaluate RT practices across England and Wales and assess readiness for protocol compliance. This study reports UK photon radiotherapy practice for oligodendroglioma and evaluates consistency relative to APPROACH protocol requirements. Methods: Between December 2022 and September 2025, photon radiotherapy centres in England and Wales (n=23) and both UK proton centres completed the FQ. The questionnaire captured routine practice in immobilisation, imaging, contouring, planning, and verification. Responses were collated by the RTTQA Group. Results: All centres routinely used thermoplastic mask immobilisation and delivered photon radiotherapy using IMRT/VMAT. Dose schedules were consistent, most commonly 54 Gy in28–30 fractions for WHO grade 2 oligodendroglioma and 59.4 Gy in33 fractions for grade 3. However, substantial variation was identified in pre-treatment imaging: CT slice thickness ranged from 1–3 mm and MRI T1 slice thickness from 0.8–3 mm, with nine centres exceeding the 1 mm protocol requirement. MRI type and sequencing were inconsistently reported, and not all centres used dedicated planning MRI scans. Marked variability was also observed in organ-at-risk (OAR) contouring. While optic pathway structures and brainstem were routinely delineated, only 4/23 (17%) centres contoured hippocampi, and none contoured the hypothalamus as standard practice. Auto-contouring tools were used in 65% of centres. Conclusions: The findings indicate broad alignment in technique and dose delivery but highlight variability in imaging and OAR delineation. Implementation of the APPROACH trial and associated RTQA processes is hoped to promote national standards in oligodendroglioma RT practice.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Medicine
Publisher:	Elsevier
ISSN:	0936-6555
Date of Acceptance:	27 July 2026
Last Modified:	10 Aug 2026 11:45
URI:	https://orca.cardiff.ac.uk/id/eprint/188824

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