Acute Lymphoblastic Leukemia (ALL) is the main neoplasia that affects children and adolescents, accounting for 25% of all types of cancer in the age group. It is a hematopoietic system neoplasia. and can be classified by several types of cell morphology, immunophenotyping, cytogenetic and molecular biology. Despite advances in treatment, up to a quarter of patients with ALL are still relapsed, and are associated with recurrent genetic conditions. In recent years, intensive efforts have been devoted to identifying the genetic factors that contribute to a leukemogenesis, influence a response to treatment and which are applied in the clinic as new prognostic tools and/or as new therapeutic targets. In this sense, this project aims to evaluate the therapeutic response and prognosis of patients with acute lymphoblastic leukemia carriers of the main genetic fusions that are believed to play an important role in the diagnosis, prognosis and targeting of therapeutic actions of ALL, such as a TCF3-PBX1, MLL-AF4, BCR-ABL, TEL-AML1 and SIL-TAL, in pediatric patients at a referral center in the State of Pará. Material and Methods: Bone marrow and peripheral blood samples were extracted from 55 patients from 0 to 18 years, with ALL, which were also submitted to data collection. Their samples were submitted to RT-PCR technique to investigate the main fusions found in leukemias. Results: Patients older than 10 years were more refractory to treatment than the other patients (p=0.017). The initial leukometry presented a mean of 92.235 leukocytes and 35.3% presented leukometry greater than 50.000, being a higher risk factor (p=0.000) and present other factors of poor prognosis as age group (p= 0.004) and Egil classification of ALL T (p= 0.001). The frequency of fusions was BCRABL-11%; MLL-AF4 = 3.6%; TEL-AML1 - 7.2%, E2A-PBX1 - 21.8% and SIL-TAL 5.4%. Patients with TEL-AML1 fusion were mostly HR (p=0.026, OR= 0.82 e IC= 0.68– 0.99), those with MLL-AF4 presented a relative risk for death of 1.33, and all died (p=0.019), those with SIL-TAL had an unfavorable age at diagnosis (greater than or equal to 10 years) (p=0.017) and initial leukometry greater than 50.000 (p=0.039). The refractoriness of the initial treatment was 9%, recurrence 18% and death 14.5%, not being significantly associated with gender, age, leukocyte count at diagnosis, cell line or presence of fusions in this limited number of patients, except for the MLL-AF4 fusion that presented a death chance ratio of 1.33 (p = 0.019) and all pacients died. Conclusion: The population studied has a worse prognosis even in those patients with favorable genetic characteristics such as TEL-AML1 fusion. The frequency of fusions in this research was high, and associated with other prognostic factors such as age greater than 10 years and initial hyperleukocytosis contributed to a worse prognosis and decrease of the therapeutic response and in addition, MLL-AF4 fusion in infants alone presented a high risk for death. The outcomes in children with ALL may be a reflection of health care conditions, socioeconomic status, and other associated genetic factors.
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