Ruivo, L.Fialho, M. PintoBaptista, D.Filipe, J.2025-03-132025-03-132024-09Ruivo L, Fialho MP, Baptista D, Filipe J. Tumour infiltrating lymphocytes characterization in advanced non-small cell lung cancer with first-line immune checkpoint inhibitors treatment. In: 36th European Congress of Pathology, Convention Centre Dublin (Ireland), September 7-11, 2024. Virchows Arch. 2024;485(Suppl 1):S450.http://hdl.handle.net/10400.21/21679Background & objectives: Tumour-infiltrating lymphocytes (TILs) may have an impact on prognosis in non-small cell lung cancer (NSCLC) and may affect the efficacy of treatment. We aim to characterize TILs in advanced NSCLC with PD-L1 score>50%, treated with first-line immune checkpoint inhibitors. Methods: We performed a single-centre retrospective study. Patients diagnosed with advanced NSCLC with PD-L1>50%, from 2017 to 2023, were selected. Medical records and histological slides from the primary tumor specimens before treatment were reviewed. Immunohistochemistry for CD20, CD3, CD8 and PD-1 was performed. Tumour and stromal TILs were scored using 0%, 25% and 50% cut-offs. Results: A total of 34 patients were included. The median age was 64 years and 74% were male. The most prevalent histological type observed was adenocarcinoma (70%). Partial response to therapy was observed in 53% of patients, disease progression was seen in 44% and only 3% had a complete response. All the samples analyzed had a lymphocytic inflammatory infiltrate, with CD3+ T lymphocytes being the most prevalent. The type of inflammatory infiltrate overlapped in all treatment response subgroups. None of the cases showed more than 50% of tumor or stromal PD-1+ inflammatory cells. Conclusion: Despite therapy with immune checkpoint inhibitors, the majority of patients showed a partial response. It seems that the type of inflammatory infiltrate did not influence therapeutic response. Tumour and stromal PD-1+ inflammatory cells were the least prevalent and PD-1 was not relevant in TILs evaluation. Multi-centre randomized studies would provide more accurate data and allow performing statistical analysis regarding the prognostic value of TILs. A second biopsy could show if there are differences in the type of inflammatory infiltrate during treatment.engLung cancerTumor-infiltrating lymphocytesconference poster10.1007/s00428-024-03880-y