Radiotherapy Quality Assurance in the SCOPE2 Trial: What Lessons can be Learned for the Next UK Trial in Oesophageal Cancer?

Aims: The SCOPE2 trial evaluates radiotherapy (RT) dose escalation for oesophageal cancer. We report findings from the accompanying RT quality assurance (RTQA) programme and identify recommendations for PROTIEUS, the next UK trial in oesophageal RT.

Maetrials and methods: SCOPE2's RTQA programme consisted of a pre-accrual and on-trial component. RTQA pre-accrual requirements included acceptable submission of 3D ± 4D benchmark contouring exercise(s) and a high-dose planning case. On-trial requirements for contouring and planning included prospective reviews (PRs) of each centre's first 3D ± 4D patient and all high-dose cases prior to formal safety review. Further PRs were at the RTQA team's discretion. Timely retrospective reviews (TRRs) were also undertaken for a random 10%. Submissions were assessed against pre-defined criteria and RT planning guidance document (RPGD). This study includes initial submissions only; subsequent resubmissions are not included in this analysis.

Results: For contouring, 30/64 (47%) pre-accrual submissions were approved. 38/64 (59%) contained ≥1 target volume (TV) unacceptable variation from protocol (UV), most commonly in CTVB and ITV. Organ-at-risk (OAR) contour review was undertaken in 28/64 (44%); 6/28 (21%) contained ≥1 UV, most commonly in heart and spinal cord. 82/126 (65%) on-trial submissions were approved. 47/126 (37%) contained ≥1 TV UV, most commonly in CTVB, GTV and ITV. For OARs, 30/126 (24%) contained ≥1 UV, most commonly in heart and lungs. On-trial contour submissions were significantly more likely to be approved than pre-accrual (p = 0.016). For planning, 32/43 (79%) pre-accrual plans were approved, those unacceptable were due to PTV coverage/conformity. 118/120 (98%) on-trial plans were approved, the remaining unacceptable were due to PTV coverage/conformity. No UVs in OAR dose constraints were observed. All on-trial submissions were approved following resubmission where necessary.

Conclusion: Despite an RPGD, contouring atlas, and similar contouring protocols from preceding trials, the SCOPE2 RTQA programme demonstrates a high frequency of UVs. Our findings inform recommendations for future oesophageal RT trials.