Clinical and safety data of a phase I/II trial with imatinib and vinorelbine for patients with metastatic breast cancer (MBC).

Abstract

e13503 Background: Imatinib is a tyrosine kinase inhibitor of bcr-abl, PDGF-R, SCF, c-Kit and abl. In solid tumors it inhibits proliferation and facilitates higher intratumoral cytotoxic drug concentrations. Vinorelbine has good tolerability and efficacy in MBC. This study evaluates the combination of imatinib and vinorelbine. Methods: In aprospective open-label, phase I/II trial 400 mg imatinib p.o. daily (amended from 600 mg) was combined with an escalating dose of vinorelbine i.v. weekly in four dose levels with 10, 15, 20, 25 mg/m² (each n ≥ 5) for pats. with MBC (which express PDGF-R-α and/or -β and/or c-kit). The last pat. of a level was treated > 28 days, before enrolment for the next dose level started. Study endpoints were feasibility and tolerability, incidence of hematological and non-hematological toxicity and clinical efficacy (data cut: 18/11/2011). A translational subprotocol is ongoing. 33 pats. have been enrolled; all dose levels have been fully recruited. 1 patient is still on study medication. Results: 32 pats. are evaluable (ITT population). 11 pats. went off study early (progressive disease, toxicity and withdrawal of consent). 22 pats. were on study >28 days (“ITT>28”). Within the ITT population the response rate (complete (CR) and partial response (PR)) was 9.4% (n=3), the clinical benefit rate CBR (CR+PR+stable disease) 50% (n=16), median time to progression (TTP) 155 days. 21.3% were on study medication >6 months, 15.2% > 12 months (mean 133 days, 15-617 days). Within “ITT>28,” the response rate was 13.6%, CBR 72.7% and median TTP 176 days. Toxicities (ITT population): 21.6% severe leukopenia, 9.1% severe neutropenia (with 1 febrile neutropenia), 1 case of bowel perforation, 36% diarrhea (3% severe), 84.8% nausea (severe 15.2%), 48.5% vomiting (severe 9.1%), 27.3% infections (severe 6.1%), 12.1% periph. neuropathy (severe 9.1%) and 36.4% dyspnea (3% severe). 1 patient on study medication died (non drug related). Conclusions: The combination of imatinib and vinorelbine in MBC appeared to be feasible and tolerable. A CBR of 50% (ITT) in pre-treated pats. proves the efficacy of this combination. Although toxicities were frequent, they appeared to be manageable.