Long-term follow-up of imatinib in pediatric Philadelphia chromosome-positive acute lymphoblastic leukemia: Children's Oncology Group Study AALL0031

We previously reported preliminary findings that post induction imatinib mesylate (340 mg/m(2)/day), in combination with intensive chemotherapy, resulted in outcomes similar to blood and marrow transplant (BMT) for pediatric patients with Philadelphia chromosome-positive (Ph +) acute lymphoblastic leukemia (ALL). We now report 5-year outcomes of imatinib plus intensive chemotherapy in 91 children (1-21 years) with and without allogeneic BMT (N = 91). We explore the impacts of additional chromosomal abnormalities and minimal residual disease (MRD) by flow cytometry on outcomes. The 5-year disease-free survival was similar for Cohort 5 patients, treated with chemotherapy plus imatinib (70% +/- 12%, n = 28), sibling donor BMT patients (65% 11%, n = 21) and unrelated donor BMT patients (59 +/- 15%; P = 0.60, n = 13). Patients with additional cytogenetic abnormalities had worse outcomes (P = 0.05). End induction (pre-imatinib) MRD was not prognostic for Cohort 5 or allogeneic BMT patients, although limited by small numbers. The re-induction rate following relapse was similar to other higher-risk ALL groups. Longer-term follow-up confirms our initial observation of substantially good outcomes for children and adolescents with Ph + ALL treated with imatinib plus intensive chemotherapy with no advantage for allogeneic BMT.