# Real-world treatment patterns and outcomes among patients with HER2-positive unresectable or metastatic breast cancer in China

## TL;DR

This study examines real-world treatment patterns and outcomes for HER2-positive metastatic breast cancer patients in China, highlighting shifts in therapy and factors influencing treatment choices.

## Contribution

The study provides real-world evidence on treatment trends and outcomes for HER2-positive metastatic breast cancer in China, including associations between patient characteristics and treatment regimens.

## Key findings

- Dual anti-HER2 monoclonal antibody therapy was the most common first-line treatment for HER2-positive metastatic breast cancer.
- Median real-world progression-free survival declined from 11.04 months in first-line to 7.59 months in second-line treatment.
- Longer disease-free interval and use of dual anti-HER2 therapy in first-line treatment were linked to better progression-free survival.

## Abstract

Breast cancer is now the most commonly diagnosed cancer in the world and the leading cause of cancer mortality in women worldwide. In past few years, anti- human epidermal growth factor receptor-2 (HER2) therapy for metastatic breast cancer (mBC) has rapidly altered in China. This study aimed to describe treatment patterns and outcomes in patients with HER2-positive unresectable or metastatic breast cancer in the real-world setting.

This multicenter, retrospective analysis evaluated the treatment patterns and the efficacy in newly diagnosed HER2+ mBC patients between Jan 1, 2020 and Aug 31, 2022. Electronic medical records from 5 cancer centers in China were used.

Among 865 patients, the most common first-line (1L) treatment regimen was dual anti-HER2 blockade monoclonal antibody-based therapy (Dual anti-HER2 mAB: 36.07%), followed by single anti-HER2 blockade mAB-based therapy (Single anti-HER2 mAB: 21.97%) and single Tyrosine Kinase Inhibitor-based therapy (Single TKI: 19.19%). In the second-line (2L), the primary treatment was single TKI regimen (35.45%), followed by TKI+anti-HER2 blockade mAB-based therapy (TKI+anti-HER2 mAB: 16.36%) and single anti-HER2 mAB (15.15%). De novo mBC at initial diagnosis, recurrence post 6 months of (neo)adjuvant treatment, absence of brain metastasis, and younger age, were associated with the choice of dual anti-HER2 mAB regimen in 1L treatment. Conversely, patients receiving anti-HER2 therapy in (neo)adjuvant setting, having brain metastasis, and experiencing a recurrence within 6 months were more likely to receive TKI-based regimen. The median rwPFS of 1L and 2L treatment declined sequentially, with values of 11.04 [95% confidence interval (CI) 10.19–12.03] months and 7.59 (95% CI 6.21–9.20) months, respectively. Longer disease-free interval (DFI) and the choice of dual-anti HER2 regimen in 1L treatment were associated with longer rwPFS.

The results of this study provide valuable real-world insight into HER2 positive mBC treatment trends and clinical outcomes, informing subsequent patient management.