Phase II study of weekly paclitaxel for docetaxel-resistant metastatic breast cancer in Japan.

The purpose of the study was to evaluate the efficacy of weekly paclitaxel (PTX) against metastatic breast cancer (MBC) that was resistant to docetaxel (DTX) given every 3 weeks. A multicenter phase II study was performed. Women with MBC resistant to DTX were eligible for enrollment. DTX resistance was defined as no tumor response to DTX and stable disease, partial response, or complete response to DTX preceding disease progression. PTX 80 mg/m(2) was administered over 1 hour once a week for 3 weeks per 4-week cycle. Among 47 enrolled patients, 46 patients were assessable for response and toxicity. The overall objective response rate (complete responses [CRs] and partial responses [PRs]) was 17.4% and overall clinical benefit rate (CRs, PRs, and stable disease >or=24 weeks) was 26.1%. The median time to progression was 11 weeks. There were a few severe hematologic toxicities related to the therapy, with grade 4 neutropenia (4.3%) and thrombocytopenia (2.2%). Grade 3 anaphylaxis and grade 3 neuropathy were observed in one patient (2.2%) each. The median delivered dose intensity was 77.6 mg/m(2)/week, 97.1% of the planned dose intensity. Weekly PTX has activity in patients with MBC resistant to DTX every 3 weeks.