Background: Topotecan is a new antineoplastic agent with a broad spectrum of activity. The purpose of this Phase I trial was to define the maximum tolerated dose of topotecan when added to the widely used combination of paclitaxel and carboplatin.
Methods: Patients with advanced cancer that was refractory or resistant to standard treatments were treated with paclitaxel, carboplatin, and topotecan; doses were escalated in sequential cohorts of patients. After definition of the maximum tolerated dose without cytokines, granulocyte-colony stimulating factor (G-CSF) was added and further dose escalation was attempted.
Results: The maximum tolerated doses were: paclitaxel, 135 mg/m2, as a 1-hour intravenous (i.v.) infusion on Day 1; carboplatin, area under the curve 5.0, on Day 1; and topotecan, 0.75 mg/m2, i.v. on Days 1, 2, and 3; the regimen was repeated every 21 days. Myelosuppression, particularly thrombocytopenia, was the dose-limiting toxicity with this three-drug combination. Nonhematologic toxicity was uncommon. The addition of G-CSF did not allow substantial dose escalation because thrombocytopenia was uneffected by this agent. Eleven of 25 patients had major responses to this combination, including 8 of 14 patients with previously treated small cell lung carcinoma.
Conclusions: The combination of paclitaxel, carboplatin, and topotecan is feasible, although only relatively low doses of all three drugs can be tolerated due to myelosuppression. This regimen showed a high level of activity in these patients with refractory cancer, and merits further investigation.