Abstract P6-17-23: Randomized phase II study of lapatinib plus vinorelbine versus vinorelbine in patients with HER2 positive metastatic breast cancer progressed after lapatinib and trastuzumab treatment

Abstract

Abstract Background The continuum of anti-HER2 agents is regarded as a standard strategy for HER2 positive metastatic breast cancer patients who had progressed disease with anti-HER2 agent- containing treatments. However, there has been lack of data on which agents should be continued and how long continuous anti-HER2 therapies would be effective. This study was aimed to evaluate the efficacy of lapatinib plus vinorelbine in HER2 positive metastatic breast cancer patients who had progressed on both trastuzumab and lapatinib treatments. Methods A total of 149 patients were randomly assigned to lapatinib with vinorelbine (LV) (n=75; laptinib, 1000mg daily ; vinorelbine 20mg/m2 D1,D8 q3w) or vinorelbine alone (V) (n=74; 30mg/m2 D1,D8 q3w). The stratification factors were followings; 1) visceral metastasis, 2) previous response to lapatinib treatment, CR+PR vs. SD ≥ 12 weeks. The primary endpoint was progression free survival (PFS) rate at 18 weeks. The secondary endpoints were objective response rate (ORR), PFS, and overall survival (OS). Results : Both arms were well balanced in various clinical factors. The median number of previous anti-HER2 therapies were 2 (range 2-5). There was no significant difference in PFS rate at 18 weeks between LV and V arms (44.0% vs 36.5%, p=0.44). ORR was 19.7% in LV arm and 16.9% in V arm (p=0.881). PFS and OS did not differ between two arms (LV vs V; median PFS, 16weeks vs 12 weeks, HR= 0.86, 95% CI 0.61-1.22, p=0.41; median OS, 15.0 months vs 18.9 months, HR= 1.07, 95% CI 0.72-1.58, p=0.72). In subgroup analysis, there was no difference in PFS and OS between two arms according to previous response to lapatinib (median PFS, CR+PR vs. SD ≥ 12 weeks, 12.1weeks vs.17.4 weeks; HR= 1.242, 95% CI 0.881-1.751, p=0.215; median OS, 14.9 months vs. 19.4 months; HR= 1.179, 95% CI 0.797-1.744, p=0.41). Most common adverse events in both arms were neutropenia which was more often observed in V arm (55% vs 73%, p=0.03). Overall, the profiles of adverse events were similar in both arms and all were manageable. Conclusion Lapatinib plus vinorelbine treatment was tolerable, however, it did not demonstrate the clinical benefits compared to vinorelbine alone in HER2 positive metastatic breast cancer patients after progression on both trastuzumab and lapatinib. Citation Format: Sim SH, Park IH, Jung KH, Kim S-B, Ahn J-H, Lee K-H, Im S-A, Im Y-H, Park YH, Sohn JH, Kim YJ, Lee S, Kim H-J, Chae YS, Park K-H, Nam B-H, Lee KS, Ro J. Randomized phase II study of lapatinib plus vinorelbine versus vinorelbine in patients with HER2 positive metastatic breast cancer progressed after lapatinib and trastuzumab treatment [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-23.