Capizzi Escalating Methotrexate Versus High Dose Methotrexate in Children with Newly Diagnosed T-cell Lymphoblastic Lymphoma (T-LBL)

T-cell lymphoblastic lymphoma (T-LBL) which involves 90% of LBL cases is the second most common subtype of non-Hodgkin lymphoma (NHL) in children and adolescents. With current treatment, event-free survival (EFS) rates vary between 75%85%. Poor probabilities of survival (1015%) for patients after relapse leave no room for treatment de-escalation in frontline protocols. Limitations in numbers of newly diagnosed patients impeded evaluation potential prognostic markers and validation or conducting clinical studies.

In the GER-GPOH-NHL-BFM-95 study, the prophylactic cranial radiation was omitted, and the intensity of induction therapy was decreased slightly. There were no significant increases in CNS relapses, suggesting cranial radiation may be reserved for patients with CNS disease at diagnosis. The 5-year EFS was worse in NHL-BFM-95 (82%) than in NHL-BFM-90 (90%). It was proposed that the major difference in EFS between NHL-BFM-90 and NHL-BFM-95 resulted from the increased number of subsequent neoplasms observed in NHL-BFM-95.

Two different MTX intensification strategies are used commonly: HD-MTX with leucovorin rescue, and Capizzi-style MTX without leucovorin rescue plus PEG-ASP (C-MTX). Although superior outcome of patients with T-ALL receiving C-MTX compared with HD-MTX on the AALL0434 trial, the 2 approaches had not been compared directly in patients with T-LBL.

POG 9404: the small cohort (n = 66) of lymphoma patients who did not receive HD-MTX, the 5-year EFS was 88%. Of note, all of these patients received prophylactic cranial radiation therapy, which has been demonstrated not to be required in T-cell lymphoblastic lymphoma (T-LBL) patients.

COG-A5971 evaluated 2 strategies for CNS prophylaxis without CNS irradiation [5]. Patients were randomly assigned to receive HD-MTX in interim maintenance (BFM-95) or intrathecal chemotherapy throughout maintenance (CCG-BFM). The overall incidence of CNS relapse was 1.2%, and there was no difference between the treatment arms for CNS relapse, DFS, or OS. Minimal disseminated disease (MDD) >1% by FLOW at diagnosis was shown to be associated with a worse outcome in this trial (a BFM backbone containing HD-MTX). Measurement of bone marrow MDD at diagnosis with sequential response monitoring through peripheral blood during remission induction to aid treatment stratification was also suggested in an early COG study. The prognostic significance of MDD at End-of-Induction (EOI) or End-of-Consolidation (EOC) for T-LBL patients with positive MDD at diagnosis is still unclear.

COG AALL0434: the COG ABFM regimen with C-MTX provided excellent DFS without cranial radiation for patients with standard risk T-LBL (85%, Arm A, n=82, completed 64) and high risk T-LBL (85%, Arm A, n=61, completed 51) although patients with CNS 3 were not included. It appears that C-MTX may have negated the prognostic impact of MDD.

Nelarabine is unavailable in mainland China at this time, which did not show benefit in COG AALL0434 study.

AALL07P1: 10 patients with T-LBL in first relapse treated with a 4-drug induction regimen adding bortezomib: 7 had a response (1 had a complete response, 2 had unconfirmed complete responses, and 4 had partial responses)

COG AALL1231 for T-LBL: the 4-year EFS and OS were better in bortezomib group than the control group (86.4% and 89.5% vs. 76.5% and 78.3%, p=0.041 and 0.009, respectively.). Incorporating bortezomib into standard therapy for de novo T-LBL appears beneficial.

A biopsy for pathological examination of a mediastinal residual mass is a clinical dilemma. Currently, conventional imaging is still considered as the "standard" modality for evaluating pediatric patients with NHL at diagnosis and subsequent response. There remains controversy on PET/CT interpretation in children with NHL. Large prospective studies in pediatric patients with T-LBL regarding PET/CT value for this is scarce.

Although an overlap in morphology and immune-phenotyping exists in T-LBL and T-cell acute lymphoblastic leukemia (T-ALL), different disease distribution suggests possible different genetic profiles and pathogenesis. Except for stage, none of other parameters is used in the current stratification system outside of clinical trials for T-LBL (several candidates, but none have been validated sufficiently). Little is known about biomarkers with prognostic relevance for T-LBL. To improve risk stratification strategy and better understand biologic rationale for incorporating novel therapies (chemicals, target agents and immunotherapy) into a conventional chemotherapy backbone, translational research to identify molecular markers with prognostic relevance in T-LBL is highly recommended.

With the current treatment, around 1% pediatric patients with T-LBL will not achieve remission at the end of Induction (induction failure). The optimal treatment for this small subgroup is largely unclear. The BFM HR Blocks usually are applied to these patients even though the efficacy is unknown. Novel targeted therapies are needed for use. Dasatinib is identified as a targeted therapy for T-cell ALL in preclinical drug screening.