Central Nervous System Status is Prognostic in T-Cell Acute Lymphoblastic Leukemia: A Children's Oncology Group Report.

To determine the prognostic significance of central nervous system (CNS) leukemic involvement in newly diagnosed T-cell acute lymphoblastic leukemia (T-ALL), outcomes on consecutive, phase 3 Children's Oncology Group (COG) clinical trials were examined. AALL0434 and AALL1231 tested efficacy of novel agents incorporated into augmented Berlin-Frankfurt-Münster (aBFM) therapy. In addition to testing study-specific chemotherapy through randomization, the AALL0434 regimen delivered cranial radiation (CRT) to the majority of subjects (90.8%), while AALL1231 intensified chemotherapy to eliminate CRT in 88.2% of subjects. In combined analysis of 2,164 T-ALL subjects (AALL0434: 1,550; AALL1231: 614), 1,564 were CNS-1 (72.3%), 441 CNS-2 (20.4%), and 159 CNS-3 (7.3%). The 4-year event-free survival (EFS) was similar for CNS-1 (85.1±1.0%) and CNS-2 (83.2±2.0%), but lower for CNS-3 (71.8±4.0%); p=0.0004. Subjects with CNS-1 and CNS-2 had similar 4-year overall-survival (OS) (90.1±0.8% and 90.5±1.5%), with OS for CNS-3 (82.7±3.4%); p=0.005. Despite therapeutic differences, outcomes for CNS-1 and CNS-2 were similar regardless of CRT, intensified corticosteroids or novel agents. Except for significantly superior outcomes with nelarabine on AALL0434 (4-year disease-free survival 93.1%±5.2%), EFS/OS was inferior with CNS-3 status, all of whom received CRT. Combined analyses of over 2,000 subjects with T-ALL, found that those with CNS-1 and CNS-2 status at diagnosis had similar outcomes. Unlike with B-ALL, CNS-2 status in T-ALL does not impact outcome in the context of aBFM therapy, without additional intrathecal therapy, with or without CRT. Although nelarabine improved outcomes for those with CNS-3 status, novel approaches are needed for further improvements.