Cohorts of 3-6 patients receive escalating doses of ixabepilone until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which at least 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. Once the MTD is determined, at least 6 but no more than 12 patients are treated at the recommended phase II dose.