Phase II study of lapatinib in combination with vinorelbine, as first- or second-line therapy in women with HER2-overexpressing metastatic breast cancer.

Abstract

621 Background: Lapatinib (L), an inhibitor of epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2) is approved in combination with capecitabine for second-line treatment of HER2+ metastatic breast cancer (MBC). Vinorelbine (V)is a semi-synthetic vinca alkaloid approved for use in patients (pts) with MBC. A previous phase I trial provided a maximum tolerated dose of L plus V. Methods: This was a multicenter, phase II study (LPT111110; NCT00709618) to evaluate the efficacy and safety of L plus V in women with histologically confirmed stage IV HER2+ MBC, ≤1 prior chemotherapeutic regimen (no prior L or V was allowed; prior trastuzumab was permitted) and a Zubrod performance status of 0-2. Pts received L (1500 mg daily) plus V (20 mg/m2IV on Days 1, 8, 15) in a 4-week treatment cycle until disease progression or study withdrawal. Primary endpoint: overall response rate (ORR). Secondary endpoints: progression-free survival (PFS), overall survival, time to response (TTR), duration of response (DOR), time to progression, and safety assessments. Results: The study was terminated after three years due to slow enrollment; 60 pts were planned and 44 enrolled and were treated. The ORR was 41% (95% CI: 26.4%-55.4%; 4 complete responses, 14 partial responses). Investigator-assessed median (95% CI) PFS, TTR, and DOR were 24.1 (16.9-36.7), 7.5 (7.1–8.1), and 32.0 (18.0-42.3) weeks, respectively. Survival data are not available since data collection was terminated after discontinuation of study treatment. All pts experienced at least 1 adverse event (AE). Conclusions: The combination of L plus V resulted in a 41% ORR and was generally well tolerated. However, definitive conclusions could not be drawn as the study was terminated early and not powered for inference testing. Further exploration of L plus V is warranted to clearly define the role of this novel combination in the treatment of HER2+ MBC. Clinical trial information: NCT00709618. [Table: see text]