ESTRO 38 Abstract book

S216 ESTRO 38

plans without deviations were graded as ‘acceptable-per protocol’. Variations in TVD which were unlikely to affect the trial outcome were graded as ‘acceptable’, whilst those with a potential impact graded as ‘unacceptable’. Unacceptable deviations were further categorised according to their potential impact on tumour control probability (TCP) and toxicity. An initial review was conducted by an experienced RTQA reviewer; plans with deviations underwent a secondary review by the RTQA lead for the SCOPE2 trial. Reviewers were blinded to the trial treatment arm & recruiting centre. Results 32 RT plans were reviewed (19 upper/mid and 13 lower third oesophageal tumours) with 463 protocol items in total (figure 1). Overall, 15 (47%) plans were deemed to have either acceptable or no deviations, the majority of which had upper/mid oesophageal tumours; 9 (28%) such plans did not have any deviations at all. 17 (53%) plans had at least one unacceptable deviation, the majority being lower third oesophageal tumours. The pre-trial benchmark test case was for a mid-oesophageal tumour; lower third TVD and elective lymph node irradiation (ELNI) is more complex and was not assessed with a benchmark case which may explain the higher number of unacceptable deviations for this sub site. When the total number of protocol items was assessed, 413 (89.2%) were acceptable-per protocol; 18 (3.9%) were graded as acceptable deviations. 28 (6.0%) protocol items were graded as unacceptable, 8 (1.7%) of which were deemed unlikely to affect tumour control probability (TCP) or treatment-related toxicity rates (table 1).

receiving radical RT or chemo-RT(65Gy in 30 fractions) were eligible for the study. DW- MRI images were acquired immediately prior to fraction 1, and repeated immediately before 11. MRI scans were acquired on a GE Signa 1.5T HDxT scanner including T1PCFS image with slice thickness of 3mm. Diffusion weighted images were acquired using a single shot EPI sequence with five b-values between 0 and 1000 s/mm 2 .Parallel imaging was utilised to reduce distortion in the images. Apparent diffusion coefficient (ADC) maps were calculated using a monoexponential fit. A clinical oncologist, radiologist and RTT delineated GTV on axial slices on MR baseline and repeat MR to evaluate volume change. For ADC measurements, a ROI was defined on T1PCFS, copied to DW b=0 image, slightly adjusted for artefacts and patient motion. This volume was then copied to the ADC map. To ensure ROI include only disease, an inner margin of 1mm was created. ADC was recorded for each ROI, and % ADC change was calculated. Results 20 patients with intermediate-high risk, locally advanced OPSCC were included in the analysis. Primary GTV volumes were successfully delineated in 18/20 patients using the described method Figure 1. Mean (SD,range) GTV_T1_Base was 15.1cm 3 (8.5, 3.3-34.2) with GTV_T1_Rpt volume reducing to 8.3cm 3 (6.3, 0.1-18.1). On b value 0 images, GTV_b0_Base volume was 12.4cm 3 (8.1, 2.1-26.1), reducing to 6.9cm 3 (5.6, 0.1-17.0) on GTV_b0_Rpt.

Conclusion There are many challenges in quantifying ADC as a predictor of outcome. We imported MR scans into the treatment planning system, allowing 3D ROI to be created. Here we described a standardised method of creating a ROI for repeated assessment of volume change and ADC within a large clinical study. MERINO study will use these analytical method for all patients. 1.Paterson, C et al.The MeRInO study.Clinical and Translational Radiation Oncology , Volume 2 , 13 - 18 OC-0416 Assessing the quality of oesophageal cancer target volume delineation in the SCOPE1 trial S. Cox 1 , S. Gwynne 1 , J. Staffurth 2 , T. Crosby 2 1 South West Wales Cancer Centre, Oncology Department, Swansea, United Kingdom; 2 Velindre Cancer Centre, Oncology Department, Cardiff, United Kingdom Purpose or Objective The SCOPE1 trial, which standardised RT planning within the UK, demonstrated survival rates for oesophageal cancer patients treated with definitive chemoradiotherapy (dCRT) comparable with the best published results worldwide. We present the planned retrospective analysis of adherence to the trial protocol for target volume delineation (TVD). Material and Methods A single RT plan was selected at random from each of the 32 centres. Using the Global Harmonisation Group’s (GHG) system for classifying RT protocol adherence, each step (protocol item) of TVD was retrospectively assessed. RT

Conclusion Adherence to the TVD protocol in this sample from SCOPE1 was high with only 4.3% of protocol items graded as unacceptable deviations with potential clinical impact. Our results show that even with a detailed TVD protocol and benchmark case, clinically significant errors still occur. As RTQA programmes are being streamlined appropriate benchmark cases need to be carefully considered, especially for trials that may introduce a new standard of care.