ESTRO 2022 - Abstract Book

S381

Abstract book

ESTRO 2022

period C had a survival improvement compared to time period A when adjusting for clinical variables (all stages HR=0.725 (0.632-0.831), p<0.001; stage III patients HR=0.740 (0.600-0.913), p<0.005).

Conclusion This real world, big data analysis has shown that the introduction of IMRT was associated with more patients receiving curative-intent radiotherapy across all PS and stages of disease. In addition it facilitated the treatment of larger tumours that historically would have been treated palliatively. Despite treating larger, more complex tumours with curative-intent, a survival benefit was seen for patients treated when full access to IMRT was available. We acknowledge that other contributing factors such as improvement in staging and systemic therapy may have also contributed to the improved survival.

OC-0438 Proton-therapy and concurrent chemotherapy in stage III NSCLC: effects on hematological toxicity

F. Cortiula 1 , L. Hendriks 2 , M. Steens 3 , S. Dursun 4 , G. Bootsma 3 , R. Canters 1 , I. Rinaldi 1 , V.T. Taasti 5 , R. Houben 5 , K. Reynders 1 , S. Peeters 1 , A. Angrisani 1 , D. Hattu 1 , D. De Ruysscher 5 1 Maastricht University Medical Center+, Department of Radiation Oncology (MAASTRO), Maastricht, The Netherlands; 2 Maastricht University Medical Center+, Department of Pulmonary Diseases, Maastricht, The Netherlands; 3 Zuyderland Medical Centre, Department of Pulmonary Diseases, Geleen, The Netherlands; 4 Maastricht University Medical Center+, Maastricht, Department of Pulmonary Diseases, Maastricht, The Netherlands; 5 Maastricht University Medical Center+, Department of Radiation Oncology (MAASTRO) , Maastricht, The Netherlands Purpose or Objective The primary aim of this study was to assess whether intensity modulated proton therapy (IMPT), compared to intensity modulated photon therapy (IMRT) can reduce hematological toxicity in patients (pts) treated with concurrent chemotherapy (CCRT) for stage III Non-Small Cell Lung Cancer (NSCLC). Materials and Methods Retrospective data completion and analysis of a 2-center prospectively collected series of patients with stage III NSCLC. Pts with stage III NSCLC, receiving CCRT between 06.16-02.21, and staged with FDG-PET-CT and MRI brain were eligible. Primary endpoint: incidence of lymphopenia grade (G) ≥ 3 in IMPT vs IMRT treated pts. Secondary endpoints: the effects of IMPT in terms of pts’ recovery after CCRT and other toxicities incidence; to investigate the association between lymphopenia and the bone marrow radiation volumes (RVs). Main exclusion criteria: invasive cancer diagnosis in previous two years, previous thoracic RT and RT dose >66 Gy. Bone marrow was defined as the sum of the following structures: sternum, scapulae, clavicles, thoracic vertebrae and ribs, delineated until the level of T12 (figure 1). RVs were retrieved from regular care RT planning. Categorical variables were compared using Chi-Square, continuous variables using t-tests or Mann-Whitney U (if applicable). Odds ratio’s were derived from logistic regression models. Alpha was set to 0.05.