Abstract P4-03-10: Clinical observation of lapatinib versus continued use of trastuzumab for trastuzumab-resistant HER2-positive advanced breast cancer

Abstract

Abstract Objective: To compare the efficacy, adverse effects and survival of lapatinib versus continued use of trastuzumab for trastuzumab-resistant human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer. Methods: Patients who began the regimen of lapatinib plus capecitabine (LC or LX) or trastuzumab beyond progression (TBP) between May 2013 and October 2016 were selected from the First Affiliated Hospital of Nanjing Medical University. All of their clinical data were recorded, including age, performance status, hormone receptor status, metastatic site, primary or acquired trastuzumab resistance, previous treatment and so on. They were followed up until death or April 30, 2017. The primary end point was progression-free survival (PFS). The efficacy and safety of the two regimens were evaluated according to Response Evaluation Criteria In Solid Tumors (RECIST) version 1.1 and Common Terminology Criteria for Adverse Events (CTCAE) version 4.0, respectively. Data were analyzed by SPSS version 19.0. Results: In total, 95 patients were identified, including 40 treated with LX and 55 with TBP. Median follow-up time was 16.0 months. There was no difference in objective response rate (ORR) and disease control rate (DCR) between the two groups. By the end of follow-up, median PFS was 6.3 months with LX and 7.1 months with TBP (P=0.676). In patients with primary trastuzumab resisitance, longer PFS was observed in LX group compared with TBP group [median PFS: 8.0 months vs. 5.3 months, hazard ratio (HR)=0.416, 95% confidence interval (CI): 0.177-0.981, P=0.038]. The incident rate of new brain metastases during treatment was 2.5% in LX group and 10.9% in TBP group, respectively (P=0.233). Both regimens showed similar outcomes in baseline brain metastases. Grade 3-4 adverse effects included diarrhea 7.5%(3/40) and hand-foot syndrome 12.5%(5/40) in LX group, along with leukopenia 18.2%(10/55), thrombocytopenia 9.1%(5/55) and nausea/vomiting 3.6%(2/55) in TBP group. Conclusion: LX and TBP were similarly effective for patients with HER2-positive breast cancer progressing on prior trastuzumab-containing therapy. Both were well tolerated in general. Lapatinib tended to reduce the risk of disease progression in patients resistant to trastuzumab primarily. LX or TBP after local treatment appeared to show no difference in treating patients with brain metastases. Citation Format: Yin Y, Li W, Huang X, Wang J, Fu Z, Li J. Clinical observation of lapatinib versus continued use of trastuzumab for trastuzumab-resistant HER2-positive advanced breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-03-10.