# Trastuzumab deruxtecan in advanced breast cancer: a real-world study of efficacy and safety in Chinese cohort with HER2-positive and HER2-low expression

## TL;DR

This study examines trastuzumab deruxtecan's effectiveness and safety in Chinese patients with advanced breast cancer, showing better outcomes for HER2-positive patients.

## Contribution

Provides real-world evidence of trastuzumab deruxtecan's efficacy and safety in Chinese patients with HER2-positive and HER2-low breast cancer.

## Key findings

- HER2-positive patients had a median progression-free survival of 14.2 months versus 8.8 months for HER2-low patients.
- Trastuzumab deruxtecan showed manageable safety with mostly Grade I-II adverse events.
- Early initiation of treatment may maximize survival benefits in advanced breast cancer patients.

## Abstract

To explore the safety and real-world efficacy of trastuzumab deruxtecan in Chinese patients with advanced breast cancer that is either HER2-positive or HER2-low expression.

A retrospective analysis was conducted on 104 patients diagnosed with advanced breast cancer who received trastuzumab deruxtecan treatment at the Affiliated Hospital of Xuzhou Medical University, with the study period spanning from January 2023 to September 2025. The primary endpoint of the study was progression-free survival, and the secondary endpoints were objective response rate, disease control rate, and safety. Progression-free survival was analyzed using the Kaplan-Meier method and log-rank test.

Among 104 patients, the median progression-free survival was 8.8 months in those with HER2-low expression, whereas HER2-positive patients exhibited a longer median progression-free survival of 14.2 months, along with superior objective response rate and disease control rate. Adverse events were reported in all patients, predominantly Grade I-II, with no new safety signals detected.

Consistent with findings from previous clinical trials, real-world evidence from this study confirms that trastuzumab deruxtecan exhibits efficacy in patients with advanced breast cancer across all HER2 expression statuses and safety profile is manageable. Earlier initiation of trastuzumab deruxtecan may maximize survival benefits. These findings help bridge the gap between clinical trial evidence and routine clinical practice.