S801
Clinical - Lung
ESTRO 2026
5 Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom
events. Esophagus Dmean showed acceptable predictive ability for grade ≥ 2 esophagitis (AUC = 0.74) with 87.5% sensitivity and 76.9% specificity at 1151 cGy (p = 0.07). Esophageal V30 demonstrated moderate predictive ability (AUC = 0.73) with 75% sensitivity and 84.6% specificity at 16% (p = 0.082), although neither reached statistical significance.
Purpose/Objective: Recent evidence identified the heart-base as a region where higher dose correlated with poorer survival. To mitigate this, a cardiac avoidance area (CAA) has been defined, and a dose limit (<19.5Gy in 20 fractions) implemented as a new standard of care at our centre in April 2023. The ongoing RAPID-RT study(1) aims to use routinely collected ‘real-world’ data to evaluate the impact of this change on survival and adverse events (AEs). This analysis compares patients treated before and after the dose limit, focusing on grades 2-5 oesophagitis and pneumonitis and the corresponding dose to thoracic organs. Material/Methods: Patients with stage 1–3 lung cancer treated with curative-intent radiotherapy ( ≥ 40Gy in >10 fractions, excluding SABR) were included. Cohort 1 (C1) comprised of patients treated without the CAA dose limit between 1/2/2022–31/1/2023 with IMRT/VMAT; cohort 2 (C2) with the new CAA dose limit between 1/5/2023–31/4/2024 with VMAT. AEs (CTCAE v5.0), reported during 6 months from first treatment, and dosimetric data, were extracted from structured electronic health records. Free-text AE annotations were transcribed into structured data for analysis. Identified grade ≥ 3 AEs underwent independent clinical review. Frequencies were compared using Chi- squared/Fisher’s exact tests; and median doses using Mann-Whitney tests. Results: C1 included 424 patients and C2 420 patients, with comparable demographic and disease characteristics (NSCLC 87%, SCLCL 12%, stage 3 > 50%). Median age was higher in C2 (72.6 vs 74.2 years, p=0.05). AE profiles were consistent across cohorts (Table 1), except for an increased frequency of grade 2 oesophagitis in C2 (35.1% vs 45.0%). The CAA dose was significantly reduced after CAA implementation (median [Interquartile range (IQR)] maximum D1cc: 13.8 [5.7-21.2]Gy vs 24.6 [4.6-41.6]Gy). Doses to other OARs were comparable between cohorts, with a non- significant increase in mean oesophagus dose in C2 (9.5 vs 11.3Gy, p=0.08). Patients with grade 2+ oesophagitis had a higher mean oesophagus dose in both cohorts compared to those without oesophagitis (17Gy vs 6Gy) and those with grade 2+ pneumonitis had a higher mean lung dose (10Gy vs 8Gy) compared
Conclusion: Consolidative hypofractionated RT using 4D planning and SIB-IMRT after induction chemoimmunotherapy appears well tolerated in NSCLC, demonstrating a low incidence of severe esophagitis. An esophageal mean dose ≥ 1151 cGy and V30 ≥ 16% were associated with an increased risk of grade ≥ 2 esophagitis. Adhering to these dose guidance—particularly in younger patients, those with advanced stage disease, or fewer induction chemotherapy cycles—may mitigate the risk of clinically meaningful esophagitis in the immunotherapy era. Keywords: NSCLC, hypofractionated RT, esophagitis Digital Poster Highlight 2859 Impact of heart-base dose limit implementation on oesophagitis and pneumonitis in lung cancer radiotherapy: RAPID-RT study Catharine Morgan 1 , Abigail Walker 2 , Rebecca Holley 3 , Harry Crawford 2 , Tom Marchant 4,3 , Evan Kontopantelis 1 , Tjeerd van Staa 1 , Kathryn Banfill 5 , Gareth Price 4,3 , Corinne Faivre-Finn 5,3 1 Division of Informatics, Imaging & Data Sciences, The University of Manchester, Manchester, United Kingdom. 2 Lung Research Team, The Christie NHS Foundation Trust, Manchester, United Kingdom. 3 Division of Cancer Sciences, The University of Manchester, Manchester, United Kingdom. 4 Christie Medical Physics & Engineering, The Christie NHS Foundation Trust, Manchester, United Kingdom.
to those without.
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