The Clinical Features and Prognosis of Early T-Cell Precursor Subtype of Lymphoblastic Lymphoma in the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 Study

Introduction: Recently, early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) was identified as a subtype of T-cell ALL (T-ALL), with distinctive gene expression and cell marker profiles. Some reports revealed that ETP-ALL was associated with a high risk of remission induction failure and relapse. In precursor T-cell lymphoblastic lymphoma (T-LBL), the clinical features and prognosis of the ETP subtype are not clear yet. In this study, we analyzed the data obtained from patients of advanced stage T-LBL to clarify the prognosis of pediatric T-LBL according to the immunophenotypes, including the ETP subtype of LBL.

Patients and methods: From November 2004 to October 2010, 136 children (aged 1–18 years) with newly diagnosed advanced stage LBL (stages III and IV) were eligible for the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 study. We analyzed their immunophenotyping data as well as the ETP subtype. The immunophenotype of T-LBL was classified into pro-T, pre-T, intermediate T, and mature T based on the European Group for the Immunological Characterization of Leukemias (EGIL) classification. The definition of ETP subtype LBL was based on a previous report from the Tokyo Children’s Cancer Study Group (Inukai et al, 2011) using a scoring system consisting of the following 11 markers: CD4, CD8, CD13, CD33, CD34, HLA-DR, CD2, CD3, CD4, CD10, and CD56. Both definitions were based on flow cytometric analysis.

Results: In this analysis, 104 (76%) patients were diagnosed with T-LBL. Sufficient data to evaluate the EGIL classification was available for 40 out of 104 patients. The remaining patients could not be classified due to incomplete immunophenotypic data. There were 1, 9, 21, and 9 cases of Pro-T, pre-T, intermediate T, and mature T, respectively. The 3-year event-free survival (EFS) of pro-T/pre-T and intermediate T/mature T was 80.0 ± 12.7% and 76.7 ± 7.7%, respectively (P = 0.7586). For evaluating the ETP subtype of LBL, sufficient data, obtained by using the scoring system with 11 markers, was available for 40 patients. Eight (20%) and 32 (80%) patients were classified as having ETP and non-ETP subtype, respectively. Bone marrow involvement for patients with ETP and non-ETP subtype was observed in 7 (88%) and 11 (34%) cases, respectively (P = 0.014). Central nervous system involvement in patients with ETP and non-ETP subtype was observed in 2 (25%) and 0 cases, respectively (P = 0.036). Thus, stage IV classification was more frequently observed in patients with ETP subtype than in patients with non-ETP subtype (P = 0.014). The 3-year EFS of patients with ETP and non-ETP subtype were 75.0 ± 15.3% and 71.9 ± 8.0%, respectively. There was no significant difference in EFS between patients with ETP and non-ETP subtype (P = 0.8281).

Conclusion: For 40 out of 104 T-LBL patients, sufficient data was available to evaluate the immunophenotype for EGIL classification and ETP subtype. There was no significant difference in EFS according to the immunophenotypic subtype of T-LBL. In contrast to T-ALL, ETP subtype in LBL was not statistically related to EFS in this analysis.