ESTRO 2021 Abstract Book

S326

ESTRO 2021

OC-0426 Prospective knowledge-based planning for personalised plan QA in a multi-centre kidney SABR trial N. Hardcastle 1 , O. Cook 2 , X. Ray 3 , A. Moore 2 , K. Moore 3 , D. Pryor 4 , A. Rossi 2 , F. Foroudi 5 , T. Kron 1 , S. Siva 1 1 Peter MacCallum Cancer Centre, Physical Sciences, Melbourne, Australia; 2 TROG Cancer Research, Quality Assurance, Waratah, Australia; 3 University of California San Diego, Department of Radiation Medicine and Applied Sciences, San Diego, USA; 4 Princess Alexandria Hospital, Department of Radiation Ocology, Brisbane, Australia; 5 Olivia Newton-John Cancer Centre at Austin Health, Radiation Oncology, Melbourne, Australia Purpose or Objective Treatment plan quality assurance (QA) in clinical trials improves protocol compliance and patient outcomes. To date, only retrospective analysis of clinical trials exist in the literature, and these have demonstrated improved treatment plan quality and consistency. We report the results of prospective use of KBP for real- time QA of treatment plan quality in the multi-centre TROG 15.03 FASTRACK II trial, which evaluates efficacy of SABR for kidney cancer. Materials and Methods In FASTRACK II, patients received a single fraction of 26 Gy (tumour < 4 cm) or 42 Gy in three fractions. A single KBP model was generated based on single institution data from 52 patients treated under the same protocol. For each FASTRACK II patient in the KBP phase (the last 31 patients in the trial), the treating centre submitted treatment plans 7 days prior to treatment. A treatment plan was created using the KBP model, which was compared with the submitted plan for each organ-at-risk (OAR) dose constraint. A report comparing submitted with KBP plan for OAR constraints was provided to the submitting centre within 24hrs of receiving the plan. In the case the submitted plan exceeded constraint but KBP did not, or if the OAR constraint value was at least 10% lower than that in the submitted, improvement was suggested The centre could then modify the plan based on the KBP feedback, or continue with the existing plan. Results Real-time KBP feedback was provided in 24 cases. Consistent plan quality was in general achieved between KBP and submitted plans. KBP suggested potential improvement typically for volume constraints as shown in Figure 1, as opposed to near maximum constraints. KBP suggested violations on the small bowel could be rectified in three cases (Figure 1b), one of which was replanned (Figure 2a-b). In a further case, although the submitted plan met small bowel constraints, KBP review suggested dose improvements so the centre elected to replan to improve robustness of plan to small bowel position variation at treatment (Figure 2c-d). All centres indicated that KBP feedback was a useful QA check of their treatment plan.

Figure 1: Volume constraints for small bowel and stomach. Error bars on the submitted plans are ±10% of the submitted value, (threshold for suggesting plan improvement). Two horizontal lines = minor/major violation levels. Arrows on (b) indicate where submitted plan exceeded constraint but KBP did not