Background: Adult T-cell leukemia/lymphoma (ATLL) is a rare Peripheral T-cell Lymphoma subtype caused by Human T-Lymphotropic Virus 1 (HTLV-1). The disease encompasses a vast phenotype ranging from the smoldering and chronic indolent subtypes to the lymphoma and acute aggressive subtypes. Aggressive ATLL which comprise acute/leukemic, lymphoma, and other indolent subtypes with aggressive transformation tend to have poor outcome with conventional chemotherapy rarely achieving durable lasting remission. We conducted this pooled database analysis to identify key factors that affect the clinical outcomes of aggressive ATLL subtypes. Methods: To study the demographic characteristics, molecular and immunohistochemical signatures, therapeutic interventions, survival, and prognostic factors, we compiled a pooled database of 462 ATLL cases. Kaplan-Meier survival curves were constructed. Cox proportional hazards model and Log-rank tests were used to assess the influence of demographic and clinicopathologic factors on the overall survival (OS). Results: Three hundred and forty-seven aggressive ATLL patients with survival data were included in this analysis. The median OS of the whole group was 14 months, with a median OS of 12.8, 16, and 12 months for acute, lymphoma, and transformed subtypes. The median age was 54 years, with a M:F ratio of 1.1. SCT demonstrated superior OS compared to chemotherapy (28 vs. 10 months, pCitation Format: Supriya Gupta, Christopher Graham, Philip A. Haddad. Survival determinants of aggressive adult T-cell leukemia/lymphoma (ATLL): analysis of a pooled database. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4409.