Purpose: We sought to determine the tolerance of estramustine phosphate (EMP) combined with a 3-hour paclitaxel infusion in women with solid paclitaxel-pretreated solid tumors. Paclitaxel pharmacology was to be studied at the recommended phase II dose.
Patients and methods: Paclitaxel was administered to cohorts of at least three assessable patients at doses of 150, 180, 210, and 225 mg/m2, while EMP was given at 900 and 1,200 mg/m2/d in divided doses orally for 2 days preceding and on the day of paclitaxel. The pharmacologic study was performed at 225 mg/m2 paclitaxel given in the absence and 3 weeks later in the presence of EMP 900 mg/m2/d.
Results: Thirty-eight patients received a total of 178 courses. Grade 3 nausea, vomiting, and diarrhea were common at EMP 1,200 mg/m2 and paclitaxel 225 mg/ m2; this was considered the maximum-tolerated dose. Since these toxicities appeared related to EMP, the pharmacologic study used a dose of 900 mg/m2 of this agent with 225 mg/m2 paclitaxel. Antitumor activity was documented against breast and ovarian cancers at all levels. Paclitaxel pharmacokinetics without and with EMP did not differ.
Conclusion: EMP 900 mg/m2 for 3 days and 225 mg/m2 paclitaxel by 3-hour infusion are well tolerated; antitumor activity was seen in women with paclitaxel-pretreated solid tumors. This apparent enhancement of antitumor effects is unlikely to be mediated by P-glycoprotein.