ESTRO 2022 - Abstract Book

S338

Abstract book

ESTRO 2022

for the MRgRT and IMPT plans for all patients, with a mean difference of 1.2 Gy. The mean dose to the ipsilateral lung was 1.7 Gy higher on average for the accumulated IMPT compared to the MRgRT doses. The average IMPT D 1cc was higher by 5.8 Gy for the ipsilateral bronchial tree, 8.3 Gy for the heart, and 11.3 Gy for the chest wall when compared to the MRgRT D 1cc .

Conclusion For the chosen combination of margin concept and robustness settings, and without online plan adaptation, the accumulated IMPT D 1cc were higher for all OARs included in the analysis with a higher D mean to the ipsilateral lung while achieving similar target coverage. Inclusion of more patient datasets which can allow analysis of additional OARs is required to validate our findings.

PD-0399 Daily delivered dose in NSCLC patients receiving dose escalation

S.N. Thomsen 1 , D.S. Møller 1 , M.M. Knap 2 , A.A. Khalil 2 , T.B. Nyeng 1 , L. Hoffmann 1

1 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark; 2 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark Purpose or Objective Large anatomical changes may occur during RT of lung cancer potentially leading to over-dosage of organs at risk (OAR) or decrease in tumour dose. The daily delivered dose can be calculated based on CBCT scans used for patient positioning. We report on actual delivered dose, that may be calculated real time, in lung cancer patients included in the NARLAL2 dose escalation trial. Materials and Methods We investigated 12 patients included in the NARLAL2 trial. Patients were randomized between the standard arm homogeneously delivering 66Gy in 33fractions (fx) and the experimental arm delivering heterogeneous dose escalation. Dose escalation was driven by the GTV part with highest FDG-PET uptake, where the dose was escalated up to mean doses of 95Gy/33fx for primary tumour (GTV-T), and 74 Gy/33fx for malignant lymph nodes (GTV-N). The escalation dose is