P057 | HYPERLEUKOCYTOSIS AND EXTRAMEDULLARY INVOLVEMENT IN ACUTE MYELOID LEUKEMIA: THE ROLE OF ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION

Background Newly diagnosed cases of Acute Myeloid Leukemia (AML) are stratified according to the 2022 European LeukemiaNet (ELN) recommendations based on their cytogenetic and molecular profiles. However, the literature suggests that hyperleukocytosis (HL) and extramedullary involvement (EI) may affect patient outcomes and may be regarded as adverse clinical risk factors. This study aimed to evaluate 2-year overall survival (2yOS) in patients with AML undergoing allogeneic stem cell transplantation (ASCT) or chemotherapy (CT) with a specific focus on the impact of EI and HL. Materials and Methods This is a multicentric, retrospective study including patients with newly diagnosed AML between 2017 and 2023 presenting with HL, EI or both. Patients were stratified according to the ELN2022 classification into favorable (fav), intermediate (int) and adverse (adv) risk categories, and categorized based on the presence of HL or EI. Therapeutic interventions, consisting of CT or ASCT, were administered in accordance with local treatment policies. The primary endpoint of the study was 2yOS. Results We enrolled 97 patients: 83 presented with HL at diagnosis, 28 with EI, and 15 with both (Fig 1.a). 22 patients in the fav-risk group underwent ASCT, while 11 patients received CT; 30 patients in the int-risk group received ASCT, while 20 patients were treated with CT; and 7 patients in the adv-risk group underwent ASCT, while 6 patients received CT (Fig 1.b). EI and ASCT resulted associated to 2yOS both at univariate and multivariate analysis (respectively OR 1.2, p < 0.01 and OR 0.8, p < 0.001). We observed that among all risk groups, patients who underwent ASCT demonstrated better outcomes in terms of 2yOS compared to those who received CT. (respectively: fav log rank=4.62, p=0.03 (Fig 1.c); int log rank=5.54, p=0.02 (Fig 1.d); adv log rank=6.15, p=0.01[Fig 1.e]). In a subgroup analysis limited to patients with EI only, fav-risk patients demonstrated a statistically significant survival advantage in 2yOS when treated with ASCT compared to CT (log-rank = 8.33, p = 0.004 [Fig 1.f]) whereas no differences were observed in the int and adv-risk groups (int log rank=1.23, p=0.26; adv log rank=3.00, p=0.09). Conclusion In patients with AML presenting with HL or EI, ASCT is a promising therapeutic approach regardless of risk stratification according to ELN2022. Moreover, favorable-risk patients who present with EI may experience better outcomes with ASCT compared to CT alone.