Real-world data of triplet combination of pyrotinib, trastuzumab, and chemotherapy in HER2-positive metastatic breast cancer: a multicenter, retrospective study.

Background: Pyrotinib, an irreversible pan-human epidermal growth (HER) inhibitor, has proven its antitumor efficacy as a second-line treatment for HER2-positive metastatic breast cancer (HER2+ MBC) when combined with capecitabine. However, real-world data concerning the pyrotinib, trastuzumab, and chemotherapy (PyroHC) combination remains scarce.

Objectives: Our study is to report the treatment patterns, efficacy, and safety of the PyroHC combination in a real-world setting.

Design: This study enrolled patients with HER2+ MBC from five institutions in China, treated with PyroHC between June 2017 and January 2023 (ClinicalTrials.gov, identifier: NCT05839288).

Methods: We evaluated progression-free survival (PFS), objective response rate (ORR), toxicity profile, and utilized treatment regimens.

Results: Of the 135 patients in our cohort, 91.9% had prior trastuzumab exposure and 52.2% underwent at least two systematic therapy lines before receiving PyroHC. The most prevalent chemotherapies paired with PyroH were capecitabine (36.3%). Patients receiving PyroHC achieved a median PFS of 8.67 months [95% confidence interval (CI): 6.84-10.51] and an ORR of 51.3% (95% CI: 42.1-61.5%). The first-line treatment with PyroHC led to a median PFS of 14.46 months (95% CI: 6.35-22.56). Patients with brain metastases showed a median PFS of 9.03 months (95% CI: 6.56-11.50), achieving an ORR of 52.17% (95% CI: 51.74-83.39). Longer previous trastuzumab (⩾6.37 months) or lapatinib (⩾10.05 months) therapies could indicate improved PFS, while prior pyrotinib exposure negatively influenced PFS. Notably, the most common grade 3/4 adverse events were diarrhea (37.8%), which were generally manageable.

Conclusion: PyroHC shows promising efficacy and a satisfactory safety profile for treating HER2+ MBC, both as a first-line option and for heavily treated patients, including those with brain metastasis. Our findings suggest the duration and history of anti-HER2 therapy as potential predictors for PyroHC efficacy in advanced settings.