Combination of Cladribine Plus Topotecan for Recurrent or Refractory Pediatric Acute Myeloid Leukemia

BACKGROUND: The prognosis after recurrence of pediatric acute myeloid leukemia (AML) is poor, and effective salvage regimens are urgently needed. METHODS: In phase I and pilot studies, the authors evaluated the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of a 5-day course of cladribine followed by topotecan in pediatric patients with recurrent/refractory AML. The cladribine dose was escalated as follows: 9.1, 13.6, 16.3, and 19.5 mg/m(2) per day (8.9 mg/m(2) per day in the pilot study). Outcome was analyzed according to the absence (Stratum 1) versus presence (Stratum 2) of previous allogeneic hematopoietic stem cell transplantation. Twenty-six patients (20 in Stratum 1 and 6 in Stratum 2) were treated. RESULTS: The MTD was not reached in Stratum 1, but a DLT occurred at the lowest cladribine dosage (9.1 mg/m(2) per day) in Stratum 2. Febrile neutropenia was common in both strata. Nine (34.6%) of 26 patients experienced a complete response, and 7 (30.4%) achieved a partial response; 5 (19.2%) were long-term survivors at the time of last follow-up. Clinical outcome was not associated with cladribine or topotecan systemic exposure. CONCLUSIONS: The combination was well tolerated in Sratum 1, and the response rate was encouraging. This regimen offers a postrecurrence treatment alternative for patients, especially those who have received anthracycline-containing chemotherapy. Cancer 2010;116:98-105.(C) 2070 American Cancer Society.