Long-Term Outcomes of T-Cell Acute Lymphoblastic Leukemia and Risk Factors for Survival in a Multicenter Registry Study from Brazil

Introduction T-cell acute lymphoblastic leukemia (T-ALL) constitutes around 25% of all newly diagnosed cases of acute lymphoblastic leukemia (ALL) in adults. While most pediatric treatment protocols categorize patients (pts) based on their phenotype, this approach is seldom applied to adults. Nevertheless, there is a scarcity of reported cohorts specifically focusing on adult T-ALL. Often, these cases are studied alongside B-cell cases, despite their notable biological differences, or grouped with T-cell lymphoblastic lymphoma, which exhibits a more favorable prognosis compared to T-ALL. The objective of this study is to present outcomes and identify prognostic factors for survival of adults newly diagnosed with T-ALL, utilizing data from a real-world multicenter registry study conducted in Latin America. Methods This registry encompassed four different academic centers in Brazil. The study included pts aged 15 years and above newly diagnosed with T-ALL between January 2009 and June 2022. Clinical data were collected from medical records after ethical approval. Overall (OS) and event-free (EFS) survivals were calculated by Kaplan-Meier method, with Cox regression multivariate analysis (MVA) for finding risk factors and competing risk analysis for relapse. Results A total of 97 pts were included, with a median age of 27 years (range, 15 - 82). Thymic T-ALL accounted for 51% of the cases. Mediastinal bulky was found in 48% and positivity of initial cerebrospinal fluid (CSF) evaluation was 12.5% (by morphology or flow cytometry). Baseline features of this cohort are summarized in table 1. Most pts (88%) were treated with pediatric-inspired regimens (asparaginase [ASP]-based), mostly adapted GMALL (43%) and adapted BFM (22%). Native E. coli ASP was used in 76% and pegylated ASP (PEG-ASP) was used in remaining cases. During presentation or treatment, 15% of the subjects experienced thrombosis of any site, with most cases being associated with the use of ASP (64%) and diagnosed during induction (64%). Following the frontline regimen, 77.3% of pts achieved complete response (CR). Overall, 11.3% of pts died during the induction phase, while 8% were primary refractory. Univariate analysis for CR showed correlation with age (p=0.002), bulky size (p=0.016), and use of ASP (p=0.009). Median follow-up period was 6 years. Overall, allogeneic stem cell transplant (alloHSCT) was performed in 18 pts, being 11/18 in first CR. Five-year OS and 5y EFS were 43.7% (95% confiden