Toxicity and efficacy of intensive chemotherapy for children with acute lymphoblastic leukemia (ALL) after first bone marrow or extramedullary relapse.

Background: Approximately 25% of children newly diagnosed with acute lymphoblastic leukemia (ALL) will eventually experience leukemic relapse, with bone marrow being the most common site of recurrence. The ability to achieve a durable second remission is complicated by toxicity and resistant disease. We report a novel combination of chemotherapy for relapsed pediatric ALL.

Procedure: Thirty pediatric patients with relapsed medullary (n = 18) and extra-medullary (n = 12) ALL were enrolled at three pediatric institutions. Following receipt of induction and the first Block A and Block B of intensification, each patient was evaluated for toxicity, efficacy in achieving remission, and long-term survival. Additionally, minimal residual disease (MRD) detection by multidimensional flow cytometry (MDF) was performed.

Results: During induction, the major non-hematopoeitic toxicities were mucositis (30% of patients) and bacteremia (50% of patients). Two patients (7%) died of toxicity during induction. Toxicity during intensification Block 1A and 1B was markedly reduced. Eight-nine percent of patients with marrow disease achieved a remission following induction and intensification. The event-free survival (EFS) for all patients at 2 and 4 years were 60% (95% CI: 42-78%) and 49% (95% CI: 30-68%), respectively.

Conclusions: This regimen for patients with relapsed ALL was successful in achieving a second remission for the majority of patients with acceptable toxicity.