BackgroundT-cell lymphoblastic lymphoma (T-LBL) is the second most common subtype of non-Hodgkin's lymphoma (NHL) in children and adolescents. Under current treatment, the event-free survival rate (EFS) is between 75% and 85%. The unified CNCL-LBL-2017 protocol was adopted for treatment in the China-Net Childhood Lymphoma Group（CNCL）in order to standardize the diagnosis and treatment of childhood lymphoma, and improve the prognosis. This study aimed to analyze the clinical features of pediatric T-LBL and evaluate the theraputic efficacy, explore the prognostic factors.

Methods From May 2017 to June 2023, 548 newly diagnosed T-LBL patients aged ≤18 years from 29 centers in CNCL were enrolled in this study. According to clinical stage, prognostic genes and treatment response, the children were divided into low, intermediate and high risk groups, and stratified treatment was performed according to CNCL-LBL-2017 protocol modified from LBL-BFM95 trial, with follow-up until December 31, 2024. The therapies aimed at central nervous system (CNS), Cranial irradiation was omitted even for the patients with CNS involvement at the diagnosis. All patients received triple intrathecal injections, with stratified treatment based on CNS status. Patients with CNS2/CNS3 received more intrathecal injections.

Results A total of 548 patients were included. The median age of disease diagnosis was 8.0 years (range:1.0-16.0 years. There were 413 (75.4%) males and 135 (24.6%) females. The disease course of 434 patients(79.2%) was less than 30 days. Clinical staging: 1 case(0.2%) in stage Ⅰ, 3 cases(0.5%) in stage Ⅱ , 153 cases (27.9%) cases in stage Ⅲ and 391 cases(71.3%) in stage Ⅳ. 426 cases（77.7%）presented with anterior mediastinal mass, 386（70.4%）bone marrow involvement, 54（9.9%）CNS involvement. Median serum LDH value was 632 IU/L (range 108-35,645); 198 patients(36.1%) had a LDH value more than 1,000 IU/L.148 cases (27.0%) of the children had symptoms of airway obstruction at diagnosis, and 137 cases (25.0%) were accompanied by superior vena cava syndrome (SVCS). 49 cases (8.9%) were complicated with tumor lysis syndrome (TLS) during prednisone pretreatment.

There were 1 case (0.2%), 164 cases (29.9%), and 383 cases (69.9%) in the low, intermediate, and high-risk groups, respectively. The follow-up time was 44.5 (0.8, 93.9) months. The 5-year EFS rates and 5-year overall survival(OS) were 77.1±1.9% and 84.2±1.6%, respectively. The 5-year EFS rates of low, intermediate and high risk groups were 100.0%, 77.6±3.3% and 77.6±2.3%, respectively.

Recurrence/progression occurred in 98 cases (31 BM relapses, 18 CNS, 25 primary sites, 2 testicular, 22 multisystem recurrence), recurrence rate 17.9%, and the recurrence time was 11.5 (2.1, 75.6) months, in which 72 cases died and 26 cases survived. The recurrence rate of CNS is 3.3%. All patients experienced grade 3-4 hematological toxicity. Infection-related death occurred in 21 cases (3.8%). Eighty-four patients with high-risk factors or relapsed/refractory conditions received allogeneic hematopoietic stem cell transplantation in this study.

Based on Cox regression analysis, the failure to achieve complete remission at the end of induction (mid-term evaluation) (HR=8.528, 95%CI: 2.832-25.237, P=0.001) was the only risk factors for EFS rate.

Conclusion T-LBL in childhood and adolescence is highly aggressive and liable to relapse in the early stage of treatment. CNCL-2017-LBL protocol got a certain efficacy close to the results of international studies. High-intensity chemotherapy has improved the therapeutic effect for patients in the high-risk group. CNS relapse incidence rate didn't increase without cranial irradiation.

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2025
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