ESTRO 2022 - Abstract Book

S380

Abstract book

ESTRO 2022

in the elderly cohort (AUC: 0.80-0.85) but required an update of the intercept as the observed prevalences were higher than predicted. Models for dysphagia ≥ Grade 3 showed lower discrimination (AUC: 0.71-0.81) and needed recalibration for most time points for use in elderly patients. The original models for moderate-to-severe xerostomia performed well, and no model adjustments were required. For severe xerostomia, the prevalence was higher than predicted, requiring an adjustment of the intercept. These adjusted models showed comparable discrimination (AUC: 0.67-0.71) as in the original models.

Conclusion The CITOR NTCP-models perform reasonably well in elderly patients. The original NTCP-models for dysphagia ≥ Grade 2 and xerostomia could be used, with an updated intercept for some time points due to the higher observed rates than predicted. Model adjustment was also needed for the dysphagia ≥ Grade 3 NTCP-models, suggesting higher susceptibility in elderly patients for this side effect.

Proffered Papers: Lung

OC-0437 Impact of introducing IMRT on curative intent radiotherapy and survival for lung cancer

C. Chan 1 , I. Fornacon-Wood 2 , N. Bayman 1 , K. Banfil 1 , J. Coote 1 , A. Garbett 3 , M. Harris 1 , A. Hudson 1 , J. Kennedy 4 , L. Pemberton 1 , G. Price 5 , A. Salem 6 , H. Sheikh 1 , P. Whitehurst 5 , D. Woolf 1 , C. Faivre-Finn 6 1 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom; 2 University of Manchester, Institute of Cancer Sciences, Manchester, United Kingdom; 3 The Christie NHS Foundation Trust, Analytics, The Christie NHS Foundation Trust, United Kingdom; 4 The Christie NHS Foundation Trust, Radiation Related Research, Manchester, United Kingdom; 5 The Christie NHS Foundation Trust, Medical Physics and Engineering, Manchester, United Kingdom; 6 The University of Manchester, Institute of Cancer Sciences, Manchester, United Kingdom Purpose or Objective Lung cancer survival remains poor. The introduction of Intensity-modulated radiotherapy (IMRT) has allowed treatment of more complex tumours as it improves radiotherapy dose conformity and normal tissue sparing. However, implementation of IMRT for the curative-intent treatment of lung cancer has lagged behind that of other disease sites and there is limited evidence in the literature assessing the clinical impact of IMRT. In this study, we evaluated whether the introduction of IMRT has had an influence on the proportion of patients treated with curative-intent radiotherapy, and whether this has had an effect on patient survival. Materials and Methods Patients with lung cancer treated with thoracic radiotherapy at our institute between 2005-2020 were retrospectively identified and grouped into three time periods: A) 2005-2008 (pre-IMRT), B) 2009-2012 (some availability IMRT), and C) 2013-2020 (full access IMRT). Data on performance status (PS), stage, age, gross tumour volume (GTV), planning target volume (PTV) and survival were collected. The proportion of patients treated with a curative dose (>40Gy) between these periods was compared. Multivariable survival models were fitted to evaluate the hazard for patients treated in each time period, adjusting for PS, stage, age and tumour volume. Results 12,499 patients were included in the analysis (n=2675 (A), n=3127 (B), and n=6697 (C)). The proportion of stage patients treated with curative-intent radiotherapy increased between the 3 time periods, from 38.1% to 50.2% to 65.6% (p<0.001). When stage IV patients were excluded, this increased to 40.1% to 58.1% to 82.9% (p<0.001). This trend was seen across all PS and stages, and was still upheld when SABR patients were excluded from the analysis. The GTV increased across the time periods (median GTV 35.5 cm 3 [16.8, 60.1], 41.7 cm 3 [16.3, 85.8] and 47.6 cm 3 [17.6, 112.1] for groups A, B and C excluding SABR patients respectively, p<0.01) although the PTV volume did not. Curative-intent patients treated during