Dose escalation will proceed after patients at a given dose level receive 3 courses. In order to properly evaluate hematoxicity, a minimum of 3 weeks will be required before dose escalation. MTD is either the dose level immediately below the level at which 2 of 6 patients in a cohort experience nonhematologic dose limiting toxicity (DLT) or when 4 of 6 patients experience hematologic DLT.