Paclitaxel activity in heavily pretreated breast cancer: a National Cancer Institute Treatment Referral Center trial

To provide paclitaxel, an investigational drug at the inception of this study, to women with chemotherapy-refractory metastatic breast cancer and to evaluate response and toxicity in these patients.

Two hundred sixty-seven patients with progressive disease (PD) following at least two chemotherapy regimens for metastatic breast cancer and a contraindication to further doxorubicin treatment received paclitaxel either at 175 mg/m2 intravenously (IV) over 24 hours or at 135 mg/m2 if they had prior irradiation to 30% of marrow-bearing bone or a cumulative dose of mitomycin > or = 20 mg/m2.

In a subgroup of patients (n = 172) with measurable disease, four complete responses (CRs) and 36 partial responses (PRs) occurred, for an overall response rate of 23% (95% confidence interval [CI], 17% to 30%). No differences in response rates were noted according either to the number of prior chemotherapy regimens received or to whether patients were considered refractory to doxorubicin. The dose and schedule used in this trial resulted in febrile neutropenia in 45% of patients and a hospitalization rate of 49%.

Paclitaxel's activity in this multiinstitutional trial in heavily pretreated patients confirms the encouraging results attained in single-institution trials. Although at this dose and schedule paclitaxel may be considered too myelosuppressive for palliative care, supportive measures such as colony-stimulating factors and antibiotics were not used prophylactically. Current research efforts are focusing on whether paclitaxel's activity against breast cancer is dose- and/or schedule-dependent, and on what role it has in patients with less advanced disease.