ESTRO 2023 - Abstract Book

S373

Sunday 14 May 2023

ESTRO 2023

Conclusion In this propensity-matched cohort analysis of NSCLC patients treated with radiotherapy, we found no statistically significant association between the presence, location and grade of gross vascular invasion with either post-treatment haemorrhage or worse 2-year overall survival. Our findings could be relevant to the design of future studies and clinical practice. MO-0469 The addition of immunotherapy to lung cancer chemoradiotherapy: Factors associated with survival H. Huang 1 , D.H. Brand 1 , J.D. Fenwick 2 , M.A. Hawkins 1 1 University College London, Medical Physics and Biomedical Engineering, London, United Kingdom; 2 University of Liverpool, Department of Molecular and Clinical Cancer Medicine, Liverpool, United Kingdom Purpose or Objective For inoperable locally advanced non-small cell lung cancer (LA-NSCLC), treatment outcomes have been improved by adding immune checkpoint blockade (ICB) to standard concurrent chemoradiotherapy (cCRT). Trials of cCRT-ICB are heterogenous for factors such as tumour histology, PDL1 status and radiotherapy schedules. We aimed to model the ICB contribution to survival across published trials and determine whether ICB regimen-specific factors were associated with survival. Materials and Methods Observed rates of 2-year overall survival (OS) were retrieved from published cCRT-ICB studies. OS rates for cCRT alone were estimated using a published dose-response model fitted to 2-year OS rates for treatments delivering chemoradiotherapy without ICB. Net contributions (‘OS gain’) of the various ICB regimens were quantified by subtracting these model estimates of OS by cCRT alone from the published OS rates for cCRT+ICB. A meta-regression approach was used to analyse whether OS (and hence OS gain) were associated with ICB, patient and clinical factors. Survival models were fitted using maximum-likelihood estimation, comparing fit quality via the Akaike Information Criteria and likelihood ratio test. Results Population data were collated from prospective trials and institutional series with >20 cases published between 2018-2022 (Table 1).