Differential impact of asparaginase discontinuation on outcomes of children with T‐cell acute lymphoblastic leukemia and T‐cell lymphoblastic lymphoma

Abstract Background Asparaginase is essential for treating T‐cell acute lymphoblastic leukemia (T‐ALL). Despite the ongoing debate on whether T‐ALL and T‐cell lymphoblastic lymphoma (T‐LBL) are the same disease entity or two distinct diseases, patients with T‐LBL often receive the same or similar treatment protocols as those with T‐ALL. Methods The outcomes of patients with or without L‐asparaginase discontinuation were retrospectively analyzed among four national protocols: Japan Association of Childhood Leukemia Study (JACLS) ALL‐02 and ALL‐97 for T‐ALL and Japanese Pediatric Leukemia/Lymphoma Study Group ALB‐NHL03 and JACLS NHL‐98 for T‐LBL. The hazard ratio (HR) was calculated with the Cox regression model by considering L‐asparaginase discontinuation as a time‐dependent variable. Results In total, 199 patients with T‐ALL, and 133 patients with T‐LBL were included. L‐asparaginase discontinuation compromised event‐free survival (EFS) of T‐ALL patients (ALL‐02: HR 3.32, 95% confidence interval [CI] 1.40–7.90; ALL‐97: HR 3.39, 95%CI 1.19–9.67). Conversely, EFS compromise was not detected among T‐LBL patients (ALB‐NHL03: HR 1.39, 95%CI 0.41–4.68; NHL‐98: HR 0.92, 95%CI 0.11–7.60). Conclusion The effects of L‐asparaginase discontinuation differed between T‐ALL and T‐LBL. We assume that the differential impact results from (1) the inherent differential response to L‐asparaginase between them and/or (2) a less stringent assessment of early treatment response in T‐LBL than in T‐ALL. Given the poor salvage rate of refractory or relapsed T‐ALL and T‐LBL, optimization of the frontline therapy is critical, and the current study provides a new suggestion for further treatment modifications. However, larger studies in contemporary intensified treatment protocols are required