P16.06 Immunophenotyping of tumor-infiltrating T cells in primary CNS lymphoma

Abstract BACKGROUND Primary CNS lymphoma represents a malignant disease with dismal prognosis. Standard of care is high dose chemotherapy and radiation. However, this combination cannot be applied to the elderly and fragile population. Immunotherapy holds great promise to be effective in these patients. This study therefore aims to explore the phenotype of tumor-infiltrating lymphocytes (TIL) in order to analyze the potential for immune checkpoint inhibition. MATERIAL AND METHODS We performed ex vivo multicolor flow-cytometry on surgical specimens of nine patients with intracerebral lymphoma, including seven with primary CNS lymphoma after isolation of TILs following standard protocols. Data was analyzed using a Fortessa LSR flow cytometer and Diva software. The study was approved by the local ethics committee (PV4904). RESULTS Our ex vivo phenotyping demonstrated a predominant infiltration of CD8+ T cells, which outnumber CD4+ T cells by a ratio of 2:1 (p