Background: Recent studies of conventional chemotherapeutic drugs administered in metronomic therapy schedules showed remarkable inhibitory effects on tumor angiogenesis. Subsequent and prolonged tumor regression was achieved moreover by circumventing acquired drug resistance. In this study, metronomic and conventional trofosfamide were compared on human NSCLC xenograft "LX-1."
Materials and methods: In vitro cytotoxicity of trofosfamide on tumor and human umbilical cord endothelial cells was determined under normoxic and hypoxic conditions. Additionally fractions and duration of cell cycles were analyzed by flow cytometry. In vivo LX-1 xenotransplanted nude mice were treated with trofosfamide in conventional and metronomic schedules (i.p./p.o.). Tumor sections were evaluated for microvessel density (MVD), relative growth fraction and apoptosis.
Results: In contrast to the rapid growth of conventionally treated lung cancer, long lasting tumor growth retardation over the total treatment period was achieved with metronomic treatment. While growth fraction and apoptotic rate of LX-1 cells remained unchanged, the MVD was significantly reduced (50%).
Conclusion: Our results show advantages of a metronomic trofosfamide schedule compared to a conventional bolus therapy mainly due to inhibition of angiogenesis. In vitro data show that this mechanism works under normoxic and hypoxic conditions and suggest that this is in part a direct cytotoxic effect on endothelial cells.