Introduction: The liquid biopsy (LB) concept has gained significant attention in the last decade and has the potential to revolutionize cancer care. However, more validation in clinical trials is required on the value of LB in medical settings. Here, we focus on glioblastoma multiforme (GBM), a highly invasive and fatal subtype of the central nervous system malignant tumors. Circulating tumor cells (CTCs) are primary tumor cells released into the peripheral blood and migrating to distant organs. CTC presence is related to tumor spread and recurrence. In GBM, factors like short patient survival, the blood-brain barrier (BBB), and lack of lymphatic drainage in brain tissue make systemic dissemination rare but possible. Thus, noninvasive CTC detection can hold potential for diagnostic, predictive, and prognostic applications. Material and Methods: For cell stability preservation before sample processing, the peripheral blood samples from curatively resected GBM patients were collected preoperatively in Cell-Free DNA BCT® tubes (Streck, Inc.). CTCs were identified using CytoTrack CT11TM (2/C), a semi-automated immunofluorescence microscopy using glial fibrillary acidic protein, vimentin, and CD45 immunostaining, and DAPI counterstaining. The preliminary Kaplan-Maier survival analysis based on CTC positivity was performed in 39 patients with a follow-up longer than two years. Results: We analyzed the CTC presence in 100 GBM patient peripheral blood samples. The CTCs or cancer cell clusters were found in 35% of GBM patients. The Kaplan-Maier survival analysis did not show a correlation between CTC presence and survival. This phenomenon may be associated with the generally short survival of these patients, which is expected to increase with advances in oncology and palliative care and/or a possible suppression of tumor cell growth outside the CNS. Conclusions: We have observed the CTCs in the peripheral blood of GBM patients. The patient enrollment and clinical data recording are still ongoing.

Citation Format: Pavel Stejskal, Josef Srovnal, Alona Rehulkova, Ondrej Kalita, Marek Slachta, Marian Hajduch. Glioblastoma multiforme disseminates outside the central nervous system [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B026.