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Phase I and Pharmacologic Study of Infusional Topotecan and Carboplatin in Relapsed and Refractory Acute Leukemia

Authors' Affiliations: ¹ Division of Hematology, Department of Medicine; Divisions of ² Oncology Research and ³ Medical Oncology, Department of Oncology; and ⁴ Department of Biostatistics, Mayo Clinic College of Medicine, Rochester, Minnesota and ⁵ Greenebaum Cancer Center, University of Maryland, Baltimore, Maryland

Requests for reprints: Scott Kaufmann, Mayo Clinic, 1342 Guggenheim, 200 First Street Southwest, Rochester, MN 55901. Phone: 507-284-8950; Fax: 507-284-3906; E-mail: kaufmann.scott{at}mayo.edu.

Purpose: To assess the maximum tolerated dose, toxicities, pharmacokinetics, and antileukemic activity of topotecan and carboplatin in adults with recurrent or refractory acute leukemias.

Experimental Design: Patients received topotecan and carboplatin by 5-day continuous infusion at nine dose levels. Patients achieving a complete remission received up to two additional courses for consolidation. Plasma topotecan and ultrafilterable platinum were assayed on days 1 to 5. In addition, pretreatment levels of various polypeptides in leukemic cells were examined by immunoblotting to assess possible correlations with response.

Results: Fifty-one patients received a total of 69 courses of therapy. Dose-limiting toxicity consisted of grade 4/5 typhlitis and grade 3/4 mucositis after one course of therapy or grade 4 neutropenia and thrombocytopenia lasting >50 days when a second course was administered on day 21. Among 45 evaluable patients, there were 7 complete remissions, 2 partial remissions, 1 incomplete complete remission, and 1 reversion to chronic-phase chronic myelogenous leukemia. Topotecan steady-state plasma concentrations increased with dose. No accumulation of topotecan or ultrafilterable platinum occurred between days 1 and 5 of therapy. Leukemic cell levels of topoisomerase I, checkpoint kinase 1, checkpoint kinase 2, and Mcl-1 correlated with proliferating cell nuclear antigen but not with response. In contrast, low Bcl-2 expression correlated with response (P = 0.014, Mann-Whitney U test).

Conclusions: The maximum tolerated dose was 1.6 mg/m²/d topotecan plus 150 mg/m²/d carboplatin. The complete remission rate in a heavily pretreated population was 16% (33% at the highest three dose levels). Responses seem to correlate with low pretreatment blast cell Bcl-2 expression.