The clinical evaluation of nineteen instances of acute lymphoblastic leukemia in infants

[Abstract] Objective: This study aims to retrospectively review the clinical presentation and treatment outcomes of 19 cases of infant acute lymphocytic leukemia (IALL) treated at our institution, summarizing the clinical characteristics and prognostic factors of IALL. Methods: : Data from inpatient and outpatient electronic medical records of IALL patients treated at the Pediatric Hematology Department of Zhujiang Hospital, Southern Medical University, from April 2019 to April 2023 were collected. A total of 19 cases were analyzed retrospectively for their clinical manifestations, biological characteristics, treatment, and prognosis. Results: : The patients, aged between 4 and 11 months at initial diagnosis, primarily presented with fever, pallor, and hepatosplenomegaly. Among them, 10 cases (52.6%) had a peripheral white blood cell count ≥100×10^9/L at the onset. Two cases were accompanied by extramedullary infiltration, including one with testicular leukemia and another with central nervous system leukemia. All cases were immunophenotyped as B-ALL, with 9 cases (47.36%) being CD10 antigen-negative and 6 cases (46.2%) expressing myeloid antigens. Chromosome culture results revealed ectopic chromosome 11 in 10 cases (52.6%). MLL gene rearrangement was observed in 13 cases (68.4%), specifically MLL-AF4 in 8 cases, MLL-ENL in 3 cases, MLL-AF9 in 1 case, and MLL-USP2 in 1 case. According to the Interfant-06 scheme risk stratification, there were 6 low-risk, 9 intermediate-risk, and 4 high-risk cases. Treatment with the Interfant-06 protocol led to complications primarily including sepsis in 11 cases (57.9%), drug-induced liver damage in 12 cases (63.2%), diarrhea in 7 cases (36.8%), and pulmonary infections in 6 cases (31.6%). The median follow-up duration was 36 months (range 1-55 months), with a treatment-related mortality rate of 5.3% (1 child died due to septic shock), an overall survival rate of 89.5% (17/19, excluding one lost to follow-up), and a relapse rate of 21.1% (4/19, excluding one lost to follow-up), including 3 cases of MLL-ENL rearrangement and 1 case of MLL-AF4 rearrangement. All four relapsed patients achieved complete remission after second-line treatment (CAR T-cell therapy/radiation/immunotherapy), with MRD turning negative, among which 2 underwent bridging to hematopoietic stem cell transplantation. Conclusion: IALL is a rare pediatric leukemia characterized by high aggressiveness, high leukocyte counts, and frequent extramedullary infiltration. The Interfant-06 protocol offers high safety and remission rates for non-AML-like chemotherapy regimens but still poses a risk of relapse. MLL rearrangements are common in infant ALL and are associated with poor prognosis, especially MLL-ENL, which is linked to a higher rate of relapse. CAR T-cell therapy and Blinatumomab are effective treatments for achieving remission after bone marrow relapse in IALL.