ESTRO 2025 - Abstract Book

S1367

Clinical - Lung

ESTRO 2025

Material/Methods: Eligible patients: aged ≥18 years (≥20 years in Japan) with unresectable stage III EGFRm (Ex19del/L858R) NSCLC with no progression during/after concurrent/sequential CRT (cCRT/sCRT); patients with asymptomatic RP post-CRT were eligible. RT of 60 Gy ±10% (54–66 Gy) was required; recommended mean lung dose (MLD) of <20 Gy and V20 <35%. Patients were randomised 2:1 to osimertinib 80 mg or placebo QD until BICR-confirmed progression/discontinuation. Exploratory analysis: best objective response (BoR) by cCRT/sCRT. Multivariate logistic regression analysis is being conducted to examine baseline factors, including RT modalities/dosing parameters, associated with RP. DCO: 5 Jan 2024. Results: Overall, 216 patients were randomised (osimertinib n=143; placebo n=73). Baseline characteristics were generally balanced across osimertinib/placebo arms: cCRT 92/85%; sCRT 8/15%, respectively. All patients received prior CRT with RT dose of 60 Gy ±10% (54–66 Gy); most commonly as 30 fractions of 2 Gy (osimertinib 55%, placebo 55%). Median lung dosimetry parameters were similar between osimertinib/placebo arms: MLD 15/15 Gy; lung V20 26/26%; lung V5 54/52%, respectively. BoR in patients who received cCRT or sCRT demonstrated osimertinib benefit vs placebo; cCRT: complete response 2/123 (2%) vs 1/59 (2%); partial response 72/123 (59%) vs 19/59 (32%) and sCRT: complete response 0/10 (0%) vs 0/11 (0%); partial response 7/10 (70%) vs 4/11 (36%) in the osimertinib and placebo arms, respectively. RP (grouped term) was the only radiation-related adverse event reported (osimertinib 48%, placebo 38%), majority grade 1/2 (no grade 4/5), with few discontinuations due to RP: 5% (osimertinib) vs 3% (placebo). Of patients with RP, 87% (osimertinib) vs 93% (placebo) continued or restarted osimertinib without RP recurrence. Conclusion: RP adverse events were generally low grade and most patients with RP continued/restarted osimertinib treatment without recurrence of RP. Multivariate analyses may further assist in the discernment of etiologic risks. Efficacy and safety data for osimertinib after CRT in LAURA further establish osimertinib as the new standard of care for unresectable stage III EGFRm NSCLC. Digital Poster Impact of a repeat whole-body PET/CT in patients with locally advanced non-small cell lung cancer planned for radical radiotherapy Sara Qountich 1 , Floris Bosch 1 , Zeno Gouw 1 , Emilia Owers 2 , Else Aalbersberg 2 , Wouter Vogel 2 , Jan-Jakob Sonke 1 , José Belderbos 1 1 Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands. 2 Nuclear Medicine, The Netherlands Cancer Institute, Amsterdam, Netherlands Purpose/Objective: Several groups have reported that non-small cell lung cancer (NSCLC) may progress during the interval between diagnosis and treatment. The current ESTRO-ACROP guideline advises to have a maximum time interval of 3 weeks between initial PET/CT imaging and start of the irradiation (Nestle et al., 2018). We recently introduced the Siemens Vision Quadra, a long-axial field of view (LAFOV) PET/CT scanner, with very high sensitivity (enhancing disease detection). This study aimed to determine the impact of repeating a [ 18 F]FDG PET/CT after more than 3 weeks using a Quadra scanner on tumor staging and target definition. Keywords: Chemoradiotherapy, NSCLC, radiation pneumonitis 2652