Experience with 2-chlorodeoxyadenosine in previously untreated children with newly diagnosed acute myeloid leukemia and myelodysplastic diseases.

Purpose: To develop more effective chemotherapy regimens for childhood acute myelogenous leukemia (AML).

Patients And Methods: Between June 1991 and December 1996, we administered the nucleoside analog 2-chlorodeoxyadenosine (2-CDA) to 73 children with primary AML and 20 children with secondary AML or myelodysplastic syndrome (MDS). Patients received one or two 5-day courses of 2-CDA (8.9 mg/m(2)/d) given by continuous infusion. All patients then received one to three courses of daunomycin, cytarabine, and etoposide (DAV) remission induction therapy.

Results: Seventy-two patients with primary AML were assessable for response. Their rate of complete remission (CR) was 24% after one course of 2-CDA, 40% after two courses of 2-CDA, and 78% after DAV therapy. Of the 57 patients who entered CR, 11 subsequently underwent allogeneic bone marrow transplantation (BMT), and 40 underwent autologous BMT. Twenty-nine patients remain in continuous CR after BMT. Two patients remain in CR after chemotherapy only. The 5-year event-free survival (EFS) estimate was 40% (SE = 0.080%). Patients with French-American-British (FAB) M5 AML had a higher rate of CR after treatment with 2-CDA (45% after one course and 70.6% after two courses) than did others (P =.002). In contrast, no patient with FAB M7 AML (n = 10) entered CR after treatment with 2-CDA. Similarly, no patient with primary MDS (n = 6) responded to 2-CDA. Seven patients with secondary AML or MDS (n = 14) had a partial response to one course of 2-CDA.

Conclusion: This agent was well tolerated, and its toxicity was acceptable. Future trials should examine the effectiveness of 2-CDA given in combination with other agents effective against AML.