Pyrotinib combined with trastuzumab and chemotherapy in the treatment of HER2-positive metastatic breast cancer after the progression of trastuzumab therapy.

Introduction: Retrospective studies have shown that the continuation use of trastuzumab in HER2 positive metastatic breast cancer patients who progressed during treatment with trastuzumab still may have clinical benefits. However, the optimal strategy was still unknown. We conducted this study aiming to explore the efficacy and safety of pyrotinib plus chemotherapy with or without trastuzumab in HER2 positive MBC patients who progressed after previous trastuzumab treatment.

Methods: This was a real-world retrospective study that enrolled HER2 positive MBC patients previously treated with trastuzumab. Patients were divided into control group (pyrotinib combined with chemotherapy) and combined group (trastuzumab combined with pyrotinib and chemotherapy). The primary endpoint was progression-free survival (PFS), and the secondary endpoints were objective remission rate (ORR), disease control rate (DCR) and safety.

Results: A total of 101 patients were included in the analysis with median follow-up time of 25.5 months (95%CI, 22.5-33.0). The median PFS was 19.1 months (95%CI 10.5-NA, P = 0.039) in combined group and 11.5 months (95%CI 8.1-15.1) in control group. The ORR was 55.6% in the combined group compared with 43.0% in the control group(P = 0.299), and the DCR was 100% compared with 87.7% respectively(P = 0.028). The most common grade 3 or 4 adverse events were diarrhea [7(25.0%)], neutropenia [5(14.3%)] and leukopenia [4(11.4%)] in combined group and diarrhea [3(5.0%)], neutropenia [3(5.0%)] and leukopenia [3(5.0%)] in control group.

Conclusions: Trastuzumab combined with pyrotinib and chemotherapy showed clinical benefits and acceptable tolerance in HER2-positive MBC patients previously treated with trastuzumab. Thus, these combination regimens may be potential options for such patients.