S2542
Radiobiology – Immuno-radiobiology
ESTRO 2026
regimens: 1 × 24 Gy, 3 × 15 Gy, or 5 × 10 Gy. Peripheral blood samples were obtained at baseline, two days after the first fraction, one week and one month post- SMART. Multiparametric flowcytometry (FACS) was used to characterise immune-cell subsets and assess markers of proliferation (Ki-67), activation (e.g. HLA- DR, CD86, CD80), and costimulation (e.g. CD40). Results: Twenty-two patients were enrolled: six received 1 × 24 Gy, six received 3 × 15 Gy, and ten received 5 × 10 Gy. Seven patients were treated with ICI (PD-1/PD-L1 inhibitors) during SABR. After SMART, CD8 ⁺ T cells showed a decrease in the naïve phenotype and an increase in the effector-memory phenotype in the 3- and 5-fraction cohorts. In the single fraction scheme, the CD8 ⁺ PD1 ⁺ : aTreg PD1 ⁺ ratio significantly decreased, indicating potential immune suppression of CD8 ⁺ T-cells, while a trend towards an increase was observed in the 5-fraction scheme. Ki-67 and HLA-DR expression were significantly elevated in CD8 ⁺ and CD4 ⁺ central-memory subsets after 5-fraction SABR, suggesting robust immune activation and long-term immune memory potential. Additionally, NK effector cells showed strong activation and proliferation in the 5-fraction cohort. These results were similar in ICI- and non-ICI–treated patients. In contrast, monocyte and B- cell activation were most pronounced in the non-ICI 5- fraction cohort. Tregs were activated in all cohorts without apparent increases in proliferation. The most relevant pro-inflammatory/effector (A) and regulatory (B) changes are illustrated in Fig. 1.
Conclusion: Distinct immune signatures are observed following different SMART fractionation schedules for the treatment of adrenal metastases. The 5-fraction regimen induces the most robust immune activation, enhancing T-cell and NK-cell proliferation and activation in ICI- and non-ICI treated patients. These findings suggest that multi-fraction SABR is the most immunogenic approach, with promising potential for integration into radio-immunotherapy strategies for oligometastatic disease. References: 1 Ugurluer G, Schneiders FL, Corradini S, Boldrini L, Kotecha R, Kelly P, Portelance L, Camilleri P, Ben-David MA, Poiset S, Marschner SN, Panza G, Kutuk T, Palacios MA, Castelluccia A, Zoto Mustafayev T, Atalar B, Senan S, Ozyar E. Factors influencing local control after MR- guided stereotactic body radiotherapy (MRgSBRT) for adrenal metastases. Clin Transl Radiat Oncol. 2024 Feb 29;46:100756. doi: 10.1016/j.ctro.2024.100756. PMID: 38450219; PMCID: PMC10915494. Keywords: SABR, adrenal, immune-monitoring Multi-omics integrative modelling for SBRT in early-stage NSCLC: preliminary data from the transcriptomic task of the MONDRIAN study Stefania Volpe 1,2 , Lucia Palumbo 3 , Eltjona Mane 3 , Chiara Frascarelli 3 , Mariano Lombardi 3 , Konstantinos Venetis 3 , Michela Onza 1 , Gaia Piperno 1 , Luigi Cornacchia 1,2 , Ilaria Repetti 1 , Maria A Zerella 1 , Cristiana I Fodor 1 , Giuseppina Bonizzi 4 , Monica Casiraghi 5,2 , Lorenzo Spaggiari 5,2 , Roberto Orecchia 6 , Elena Guerini Rocco 3,2 , Nicola Fusco 3,2 , Barbara A Jereczek-Fossa 1,2 1 Department of Radiation Oncology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 2 Department of Oncology and Hemato-Oncology, Università degli Studi di Milano, Milan, Italy. 3 Division of Pathology, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 4 Biobank for Translational and Digital Medicine, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 5 Department of Thoracic Digital Poster 4848
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