ESTRO 2025 - Abstract Book

S1361

Clinical - Lung

ESTRO 2025

2563

Proffered Paper Is curatively intended reirradiation in lung cancer patients feasible? A retrospective study with clinical and dosimetric data Marianne Marquard Knap 1 , Hjørdis Hjalting Schmidt 1 , Mai-Britt Linaa 1 , Ane Appelt 2 , Line Dalgaard Graverholt 1 , Lone Hoffmann 1 1 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 2 Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom Purpose/Objective: Reirradiation (reRT) with curative intent is delivered to an increasing number of patients [1,2]. However little data exists about radiation-induced toxicity and outcome. This study aimed to evaluate lung cancer patients undergoing curatively intended reRT, in terms of grade 3-5 radiation-related toxicity and overall survival (OS). Material/Methods: From 2011 to 2023, 79 consecutive lung cancer patients were treated with curatively intended reRT type 1 or type 2 (ESTRO-EORTC consensus guidelines [1]) at our hospital. Patients were monitored with CT every third month year 1 2 and every six months year 3-5. Data on RT-related toxicity (CTCAE v5) grade 3-5 and date of death were retrospectively collected. To access the cumulative dose (EQD2 cum ) delivered, the dose of the previous treatment (RT1) was transferred to the reRT CT (RT2) using deformable image registration followed by EQD2 dose rescaling (α/β=3) assuming no tissue recovery. Results: Patient characteristics are shown in Table 1. The median time from RT1 to RT2 was 21 months (range: 4-122), and median follow-up after RT2 was 27 months (range: 2-113). Thirteen patients (16%) underwent reRT twice. Histology on biopsy was consistent between RT1 and RT2 for 63 (80%) patients. Median OS after RT2 for patients with NSCLC at RT2 and treated with stereotactic or long-course RT2 was 48 months (95%CI: 30-66) and 40 months (95%CI: 31 49), respectively (Fig 1). The six patients with SCLC at RT2 had a median OS of 16 months (95%CI: 7-25). Forty-five and 34 patients had reRT type 1 and 2, respectively. After RT1, twelve patients experienced grade 3 toxicity (esophagitis: 3, lungs: 4, skin: 1, rib/thoracic wall pain: 7), of which three had more than one episode. RT-related toxicity grade 3-5 was seen in 15 patients after RT2 (four type 1, eleven type 2): One patient died of haemoptysis with maximum EQD2 cum,esoph/bronchi <50Gy (type 2); one patient experienced grade 4 pneumothorax with max EQD2 cum,thoracic wall =130Gy (type 2); nine patients had grade 3 lung-related toxicities (dyspnoea/cough: 6 and pneumonitis: 3) with mean EQD2 cum,lung from 6.9 to 20.2Gy (six type 2 and three type 1); four patients had grade 3 rib/thoracic wall pain/fracture with max EQD2 cum,rib/thoracic wall >250Gy (one type 1 and three type 2). For patients with no thoracic pain, 31 had max EQD2 cum,rib/thoracic wall >250Gy.