Abstracts Clinical Lymphoma, Myeloma & Leukemia September 2023 S474 therapy, bleeding complication, thrombosis, anti-BCMA cellular therapy MM-074 How can Different Therapeutic Strategies and Financial Resources Impact Outcomes After Autologous Stem Cell Transplantation in Myeloma? Study in France and Algeria Emilie Martin MD1, Stéphane Morisset statistician2, Mohamad Sobh Research Associate3, Alfred Quillon MD1, Hélène Boyer PHD4, Philippe Rey MD2, Emmanuelle Nicolas Virelizier MD2, Souad Assaad MD2, Amine Belabri MD2, Yann Guillermin MD2, Laure Lebras MD2, Valérie Mialou MD5, Jean Paul Bourgeot MD5, Mélinda Teyssier Research Assistant2, Mohamed Brahimi MD6, Soufi Osmani MD6, Kamila Amani MD6, Samira Bouchama MD6, Lila Charef MD6, Nabil Yafour MD6, Anne Sophie Michallet MD2, Mohamed-Amine Bekadja MD6, Mauricette Michallet MD, PhD7 1Université Claude Bernard Lyon 1, Lyon, France. 2Centre Léon Bérard, Lyon, France. 3Ottawa Hospital Research Institute, Ontario, Canada. 4Hospices Civils de Lyon, Lyon, France. 5Etablissement Français du sang, Lyon, France. 6EHU 1er Novembre Oran, Université Ahmed Benbella 1, Oran, Algeria. 7Centre Léon Bérard, Lyon, Algeria Context: Multiple myeloma (MM) is a hematological malignancy characterized by an abnormal clonal plasma cell proliferation in the bone marrow secreting a monoclonal component. The international standard care for eligible patients consists of intensive induction therapy followed by high-dose melphalan and autologous stem cell transplantation (ASCT). Design and Setting: Our study included two groups of newly diagnosed MM patients who received a firstline treatment of double or triple induction, ASCT, with or without consolidation and maintenance. The study participants were treated in Lyon (France) and Oran (Algeria). Objective: The principal aim of this study was to evaluate the long-term outcome after ASCT in these 2 countries with different resources and to evaluate the potential consequences of non-identical access to the same therapeutic arsenal and means of early detection of relapse. Results: Despite important differences between the 2 countries, we showed a similar overall survival (OS) for the total population and patients who did not relapse and received no chemotherapy after ASCT. Surprisingly, these latter patients concerned 2/3 of Algerian patients and only 1/3 of French patients, explained by differences regarding the definition of relapse and leading to a probable underestimation in Algeria. To better explore this observation, we performed a survival analysis using the instant ratio. We found better survival in France between 0-12 months after ASCT, related to higher non-relapse mortality in Algeria. Furthermore, we showed better survival in Algeria after 48 months. This last result was enhanced by a significant difference in the time to next treatment (TTNT) between Algeria and France (median TTNT of 72.61 months and 32.77 months, respectively). For relapsing patients, we found a better OS in France for patients who received ≤3 lines of treatment after ASCT, and no difference between French patients who received ≥4 therapeutic lines and Algerian patients receiving 1 or 2 lines. Conclusion: In conclusion, waiting to re-treat MM patients in Algeria, correlated with delayed TTNT, could support the hypothesis of lower healthcare costs and therapeutic savings when comparing France and Algeria. This is strengthened by a similar global long-term OS of the 2 groups. Keywords: MM, long-term overall survival, autologous stem cell transplantation, neoplasia MM-123 Determination of T Lymphocyte Subgroups in the Bone Marrow Microenvironment in Multiple Myeloma: Can Tumor‑Directed T‑Cells Play a Role in Fighting Cancer? Ali Ünal MD, Gökçen Dinç MD, Huriye Çelikzencir MD, Nilhan Mutlu MD, Rabia Nayır MD, Sinan Kutuk MD, Gonca Günay MD, Mustafa Yavuz Köker MD Erciyes University Faculty of Medicine, Department of Internal Medicine, Department of Hematology, Kayseri, Turkey Aim: The aim of this study was to investigate the distribution of T-lymphocyte subgroups, including T8+, T4, NKT, Th1, Th2, Th17, Treg, and Th22, around the bone marrow tumor in multiple myeloma (MM) patients using flow cytometry. The interactions between the bone marrow microenvironment and plasma cells play a crucial role in the expansion of humoral and liver immunity in MM. Understanding the distribution and role of T lymphocyte subgroups in MM can contribute to the development of new immunotherapy strategies. Method: Twenty MM patients and 10 subjects with normal bone marrow were included in the study. Flow cytometric analysis was performed using superficial and intracellular staining techniques. The ratio and number of CD8+ T lymphocytes, NKT cells, and Th17 cells in the bone marrow were determined by flow cytometry. The distribution of T lymphocytes was compared based on the plasma cell ratios in the bone marrow. Results: Flow cytometry analysis revealed that T lymphocytes were directed towards the tumor periphery based on the plasma cell density in the bone marrow of MM patients. Different proportions of T lymphocyte subgroups were observed in patients with varying plasma cell ratios. Discussion: While certain T lymphocytes in the bone marrow microenvironment contribute to tumor cell development, others are believed to be involved in fighting against myeloma cells. The presence of high levels of IL-6, TGF-b, and IL-1b in the bone marrow microenvironment favors the aggregation of Th17 cells, which produce IL-17. Increased levels of IL-17 promote the growth of MM plasma cells and inhibit the immune system. These findings provide insights into the pathogenesis of MM and can aid in the development of novel immunotherapy strategies. Conclusion: The distribution of T lymphocyte subgroups in the bone marrow microenvironment of MM patients demonstrates their potential role in tumor progression and immune response. Further investigation and understanding of these interactions can contribute to the development of targeted immunotherapies for MM. Keywords: MM, multiple myeloma, T lymphocyte, immune system
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