S2543
Radiobiology – Immuno-radiobiology
ESTRO 2026
Surgery, Istituto Europeo di Oncologia IRCCS, Milan, Italy. 6 Scientific Directorate, Istituto Europeo di Oncologia IRCCS, Milan, Italy Purpose/Objective: MONDRIAN (NCT05974475) is a prospective, observational real-world study aiming to identify multi-omic biomarkers of stereotactic body radiation therapy (SBRT) response through the integration of radiomics, transcriptomics, proteomics, and clinical data in early-stage non-small cell lung cancer (ES- NSCLC). Preclinical transcriptomic analyses have suggested that distinct gene expression patterns of up- and downregulation may be associated with radiosensitivity. If validated clinically, this knowledge could support personalized treatment indications and refine prediction of clinical outcomes. Material/Methods: The first 28 consecutive patients enrolled in the MONDRIAN study—8 treated with SBRT and 20 with surgery—were included in this preliminary analysis. Baseline clinical and tumour characteristics were compared between this subgroup and the overall study population enrolled as of 12 November 2025. The Mann–Whitney U test was used for continuous variables, while the Chi-square or Fisher’s exact test were chosen for categorical variables, to exclude potential selection bias.RNA was extracted from representative Formalin-Fixed Paraffin-Embedded (FFPE) tumour blocks, and 395 immune-related genes were analyzed using a targeted Next-Generation Sequencing (NGS) panel (Oncomine™ Immune Response Research Assay, Thermo Fisher). Samples with >1,000,000 mapped reads and >800,000 valid reads were considered suitable for analysis. Differential expression analysis was performed using the R package DESeq2 (v1.38.3), with thresholds of |Log2FC| ≥ 2 and Wald Test p < 0.05. Functional enrichment analysis was carried out using ToppGene Suite. Results: No significant differences were observed between the analyzed subset and the overall MONDRIAN population, confirming that the molecular analysis group was representative and that no selection bias was introduced (Table 1).
Sixteen immune-related genes were differentially expressed: four upregulated (IFNB1, IFNA17, HLA-B, CDKN2A) and twelve downregulated (CD69, CD38, ALOX15B, EB3, SIT1, HLA-DQB2, XAGE1B, CD160, LY9, NCR3, LCK, MADCAM1) in SBRT compared with the surgery group.Functional enrichment revealed that upregulated genes were mainly involved in stress response regulation, whereas downregulated genes were enriched in immune regulatory pathways, including immune system process regulation, lymphocyte activation, leukocyte activation, and cell activation. Clustering of the 16 differentially expressed genes, clearly separating SBRT and surgery samples, is visually represented in the heatmap shown in Figure 1.
Conclusion: These preliminary findings highlight a distinct immune-related transcriptomic signature characterized by Type I Interferon activation and reduced cytotoxic activity in SBRT specimens. This suggests a specific remodeling of the post-treatment immune microenvironment that differs from surgical specimens and warrants further investigation within the multi-omics integration framework of the MONDRIAN study. Keywords: Early-stage NSCLC, gene expression
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