Background: Irinotecan (CPT-11) is a topoisomerase I inhibitor that has been confirmed to be active against a broad spectrum of neoplasms including non-Hodgkin's lymphoma (NHL). Because the combination of topoisomerase I and II inhibitors seemed to be an attractive therapeutic strategy owing to their complementary functions, we conducted a combination phase I study of CPT-11 and etoposide, a topoisomerase II inhibitor, in relapsed or refractory non-Hodgkin's lymphoma (NHL).
Methods: The starting doses of CPT-11 and etoposide were 30 mg/m2/day (days 1-3 and 8-10) and 40 mg/m2 (days 1-3), respectively.
Results: All three patients who received the starting dose developed dose-limiting toxicities including one case of grade 4 neutropenia lasting for > 7 days, one of grade 3 serum transaminase elevation and one of grade 3 hyperbilirubinemia. All three patients presented hepatotoxicity > or = grade 2. The starting dose level was judged to be the maximum tolerated dose (MTD) and further dose escalation of this combination was halted. The patient who developed grade 3 hyperbilirubinemia presented a second peak of plasma SN-38, an active metabolite of CPT-11, on the concentration-time curve for day 3, suggesting the possibility of the enterohepatic circulation of SN-38 and of a drug-to-drug interaction. No durable objective response was observed in the three patients treated at the starting dose.
Conclusions: We conclude that etoposide is not recommended for combination with CPT-11 in NHL patients because of unexpected frequent hepatotoxicities.