ESTRO 2025 - Abstract Book

S1342

Clinical - Lung

ESTRO 2025

(AOUI), Verona, Italy. 3 Department of Pathology and Diagnostics, Medical Physics Unit, Verona Univeristy and Hospital Trust (AOUI), Verona, Italy

Purpose/Objective: In advanced non-small cell lung cancer (NSCLC), immune checkpoint inhibitors (ICB) and radiotherapy (RT) are key treatment strategies. Several preclinical studies and some clinical trials have shown that RT can trigger immunomodulatory effects, suggesting that combining it with ICB may enhance systemic control through a synergistic approach Material/Methods: Patients (pts) with advanced NSCLC who received a combination of ICB and RT at primary or metastatic sites, for ablative or palliative purposes, between 2020 and 2024, were retrospectively included in the study. Progression-free survival (PFS) and overall survival (OS) were evaluated. Blood samples were collected at two time points: before ICB treatment and after RT Results: Among 44 pts with advanced NSCLC, pembrolizumab was the most used ICB (70%), followed by nivolumab (18%) and atezolizumab (12%). 82% of pts received RT during first-line treatment (1L), mostly with an ablative intent (59%). The most common sites treated with RT were lung and bone (36% each), then lymph nodes (14%), adrenal glands (9%), and liver (5%). Volumetric modulated arc therapy (VMAT) was used in most patients (95%), while a smaller group received 3D-RT (5%) We observed significantly longer progression-free survival (PFS) (23.5 vs. 6.5 months, HR 0.37, p = 0.0038) and overall survival (OS) (41.3 vs. 13.6 months, HR 0.36, p = 0.0122) in patients who received thoracic RT (tRT) compared to those who received extra-thoracic RT (eRT). Additionally, patients who received concurrent ICB and RT (cICB/RT) had better PFS (22.5 vs. 6.5 months, HR 0.30, p = 0.0003) and OS (41.3 vs. 19.0 months, HR 0.35, p = 0.0095) compared to those who received RT before or after ICB treatment (sICB/RT). Furthermore, patients who received more than 30 Gy of RT had significantly better PFS (23.9 months vs. 6.6 months, HR 0.26, p < 0.0001) and OS (41.2 months vs. 11.2 months, HR 0.22, p < 0.0001) than those who received between 20 and 30 Gy. Preliminary translational findings showed that tRT patients had higher lymphocyte levels and a lower neutrophil-to-lymphocyte ratio compared to eRT patients. Additionally, cICB/RT patients showed a more pronounced reduction in neutrophil counts. Conclusion: RT dose, target sites, treatment intent, and timing appear to influence ICB efficacy, potentially improving disease control and survival outcomes. Modulation of circulating immune cells may be key to these effects. Building on these findings, we’ve designed a prospective study to further investigate the impact of ICB and RT on tumor response and the immune landscape.

Keywords: Radiotherapy, Immunoteraphy, Immune System

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Digital Poster KRAS status in lung oligometastases treated with Stereotactic Body Radiotherapy (SBRT)

Mauro Loi 1 , Marianna Valzano 1 , Michele Aquilano 2 , Ilaria Morelli 1 , Giulio Frosini 1 , Pierluigi Bonomo 1 , Alessandra Galardi 1 , Gabriele Simontacchi 1 , Carlotta Becherini 1 , Daniela Greto 1 , Emanuela Olmetto 1 , Vieri Scotti 1 , Icro Meattini 1 , Giulio Francolini 1 , Marco Banini 1 , Andrea Romei 1 , Beatrice Bettazzi 1 , Chiara Mattioli 1 , Ilaria Bonaparte 1 , Luisa Caprara 1 , Laura Masi 3 , Raffaella Doro 3 , Lorenzo Livi 1 1 Radiation Oncology, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. 2 Cyberknife Center, Istituto Fiorentino di Cura e Assistenza (IFCA), Florence, Italy. 3 Medical Physics, Istituto Fiorentino di Cura e Assistenza (IFCA), Florence, Italy