Purpose: To determine the maximum-tolerated dose (MTD) of doxorubicin when given in combination with cisplatin and the multidrug-resistance (MDR) modulator valspodar and the remission rate induced by this combination in patients with platinum- and anthracycline-resistant ovarian cancer.
Patients and methods: Fifty-nine patients who had failed prior platinum- and anthracycline-based chemotherapy were enrolled. During the dose-finding phase, patients received a loading dose of valspodar (1.5 or 2 mg/kg) via 2-hour intravenous (IV) infusion on day 1 and continuous IV infusion (CIVI) of valspodar (2, 4, or 10 mg/kg/d) over 3 days. Doxorubicin (starting from 20 up to 50 mg/m(2)) and cisplatin (50 mg/m(2)) were administered via 15- to 20-minute IV infusions on day 3. During the efficacy phase, patients received at least two treatment cycles unless toxicity was unacceptable, and responding patients and those with stable disease received four to six cycles.
Results: All patients completed at least one cycle of combined treatment. The MTD of doxorubicin was determined to be 35 mg/m(2) when administered with valspodar at 2 mg/kg loading dose and 10 mg/kg/d CIVI plus 50 mg/m(2) cisplatin. At these doses, valspodar blood concentrations known to reverse MDR in vitro were reached in all patients. Valspodar was well tolerated at all dose levels. Dose-limiting toxicities of the combination were primarily hematologic and included febrile neutropenia and prolonged leucopenia. The addition of valspodar to the treatment did not worsen cisplatin-related toxicity. Among 33 patients treated at the MTD for doxorubicin, one (3%) had a complete response, and four (12%) had a partial response. An additional seven patients experienced a stabilization of their previously progressive disease. The survival rates at 6 and 12 months were 59% and 19%, respectively.
Conclusion: Valspodar can be safely coadministered with doxorubicin and cisplatin. Although the regimen used in this trial produced renewed responses in patients with heavily pretreated, refractory ovarian cancer, the value of valspodar in reversing resistance mediated by P-glycoprotein remains to be determined.