Preclinical and phase I study of oxaliplatin and topotecan in combination in human cancer.

BACKGROUND DNA damage caused by platinum agents is frequently followed by induction of topoisomerase I, providing a rationale for use of platinum-based compounds with topoisomerase I inhibitors. MATERIALS AND METHODS We studied the effect of a sequential schedule of oxaliplatin on day I and topotecan on days 2-5, in human colon and ovarian cancer cells in vitro, in nude mice bearing human cancer xenografts and finally in cancer patients in a phase I trial. RESULTS We demonstrated a supra-additive effect of this combination on inhibition of colony formation and induction of apoptosis in vitro. We then demonstrated that the two agents in combination markedly inhibit tumor growth in nude mice. We translated these results into a clinical setting, conducting a phase I study in cancer patients with oxaliplatin 85 mg/m2 on day 1 and topotecan at doses escalating from 0.5 to 1.5 mg/m2 on days 2-5. Sixty cycles of treatment were administered to 18 patients affected prevalently by ovarian and colorectal cancer. Combination with topotecan 1.5 mg/m2 caused a dose-limiting toxicity. Therefore the maximum tolerated dose of topotecan was 1.25 mg/m2, at which six patients experienced a mild hematological and gastrointestinal toxicity. We also obtained evidence of clinical activity, particularly in ovarian cancer. CONCLUSIONS Our results provide a solid biological and clinical rationale for a phase II trial at the recommended doses of oxaliplatin 85 mg/m2 and topotecan 1.25 mg/m2, possibly in ovarian cancer patients.