Dose escalation in oesophageal cancer: comparing pre-accrual SCOPE2/PRODIGE-26 RTTQA programmes
Jonathan Helbrow,
United Kingdom
PD-0490
Abstract
Dose escalation in oesophageal cancer: comparing pre-accrual SCOPE2/PRODIGE-26 RTTQA programmes
Authors: Jonathan Helbrow1, Owen Nicholas1, Geraint Lewis2, Ganesh Radhakrishna3, Tom Crosby4, Sarah Gwynne1,5
1South West Wales Cancer Centre, Clinical Oncology, Swansea, United Kingdom; 2Velindre Cancer Centre, Medical Physics, Cardiff, United Kingdom; 3The Christie, Clinical Oncology, Manchester, United Kingdom; 4Velindre Cancer Centre, Clinical Oncology, Cardiff, United Kingdom; 5Swansea University, Medical School, Swansea, United Kingdom
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Purpose or Objective
Radiotherapy (RT) dose escalation (DE) in oesophageal cancer has been evaluated in SCOPE2 (UK) and PRODIGE-26 (France) trials. PRODIGE-26 reports frequent RTTQA protocol deviations at the pre-accrual stage (1): we describe then compare the SCOPE2 experience.
Material and Methods
All recruiting centres without previous NeoSCOPE approval were required to submit contours using supplied 3D DICOM datasets. Those using 4D CT planning were also required to delineate a 4D dataset. Necessary clinical information and a radiotherapy planning guidance document were provided, and a “gold standard” contour agreed by the Trial Management Group.
Contour instructions included creation of CTVA, B and C, requiring automated and manual expansions plus editing for normal structures (ENS). For lower-third cases, inclusion of an elective lymph node irradiation (ELNI) volume within CTVB, and for 4D cases, creation of an ITV using the full 4D dataset, was necessary. Construction of PTV5000 (standard) and 6000 (DE) using automated expansion was mandated.
All centres were required to submit an IMRT/VMAT planning exercise using another pre-outlined 3D dataset.
Submissions were evaluated by an RTTQA reviewer using pre-defined criteria, and thence deemed “acceptable” or “unacceptable: resubmission required”. Contemporaneous feedback reports were retrospectively reviewed, and the domain of unacceptable deviations (UDs) recorded.
Results
For SCOPE2, 84 contour datasets from 33 centres were submitted. 20 were resubmissions. In total, 49/84 (58%) submitted contours were accepted: 12/15 (80%) mid-third 3D, 21/35 (60%) lower-third 3D and 16/34 (47%) 4D. CTVB (39/83, 47%) deviations, which included ENS and ELNI contouring, were most common UDs. PTV6000 (10/83, 12%) and ITV (13/43, 30%) UDs were also frequent.
52 plans from 39 centres were submitted. 9 were resubmissions. 44/52 (85%) were VMAT. 44/52 plans were accepted; 8 (15%) had UDs related to PTV coverage/conformality (c/c). OAR dose constraints were met for all.
Conclusion
A high frequency of RTTQA protocol deviations were observed at SCOPE2 pre-accrual.
By comparison, PRODIGE-26 report a similar rate of acceptable submissions (32/43, 74%), with most common contouring deviations also observed in CTV. In contrast, no UDs in CTV were seen; this difference may in part be explained by SCOPE2 ENS and 4D components. UDs in PTV c/c were similar (4/43, 9%), but in OAR constraints more frequent (7/43, 16%); this is attributed to rates of 3D conformal planning (18/43, 42%).
In conclusion, pre-accrual RTTQA findings for SCOPE2 and PRODIGE-26 are broadly comparable. The additional complexity of SCOPE2 contouring protocol and advances in planning techniques may explain differences in UD rates, but findings strongly confirm the ongoing need for rigorous RTTQA in oesophageal RT.
