ESTRO 2023 - Abstract Book

S536

Sunday 14 May 2023

ESTRO 2023

Conclusion In this interim analysis of the first ever prospective study investigating cardiac toxicity of SABR in ES-NSCLC patients, we observed that pre-existing cardiac diseases, mean RA dose and diuretic therapy increase the risk of developing G ≥ 3 CEs. Our actual results suggest a possible correlation between heart dosimetry and the development of SABR related cardiac toxicity. Completion of the patient accrual and longer follow up are required to confirm these results and to investigate for a potential impact on OS. MO-0644 Investigating the survival effect of cardiac substructure dose in a large lung radiotherapy cohort L. van der Pol 1 , J. Pomp 1 , J. Verhoeff 1 , B. Raaymakers 1 , M. Fast 1 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands Purpose or Objective Longer overall survival after lung radiotherapy raises concerns about possible treatment-induced cardiotoxic side effects. Multiple retrospective studies investigated the correlation between heart or cardiac substructure (CS) dose and survival in lung cancer patients. However, due to the general absence of cardiac substructure contours in the clinical care pathway, most studies resort to deforming all dose distributions to a representative anatomy with CS delineations. This study investigates correlation between CS dose and patient survival in a large, single-institute lung cancer cohort with the help of AI-generated CS contours. Materials and Methods We included 1579 lung cancer patients, aged between 36 and 93 years old (median: 70), T-stage 1-4 with median survivals of 51, 39, 21, 18 months respectively, 58% male, that were treated with thoracic radiotherapy between 2009 and 2019. Re- irradiated patients were excluded. A convolutional neural network, trained for this study with 40 patients, created CS contours for each patient. Contouring performance was ensured through random spot checks. As dose effects on organs are traditionally considered as either serial or parallel, D0.1cc (as a surrogate for max. dose) and Dmedian were selected. Planned D0.1cc and Dmedian to CS, the whole heart, and lungs were extracted. Univariant Cox regression was used to find significant correlations between dose and survival. Hereafter, multivariate analysis was used to identify significant correlations, while stratifying for tumor stage, pathology, age, and gender. A Bonferroni-Holm correction was applied. Results Univariate Cox regression showed statistical significance for the correlation between dose to all investigated structures and survival except for 3 of the DVH points; left ventricle D0.1cc, Dmedian and left lung Dmedian. On multivariate analysis only DVH points for the left atrium (D0.1cc) and right lung (Dmedian) remained significant (see Table 1). Hazard ratios were