# Efficacy and safety of pyrotinib-based regimens in patients with HER2-positive stage III/IV breast cancer: a real-world retrospective study in China

## TL;DR

This study shows that pyrotinib is effective and well-tolerated in treating advanced HER2-positive breast cancer in real-world patients in China.

## Contribution

The study provides real-world evidence on the long-term efficacy and safety of pyrotinib in HER2-positive breast cancer patients in China.

## Key findings

- The objective response rate was 62.2% and median progression-free survival was 12.0 months.
- Patients with fewer metastatic sites and those on first-line treatment had longer progression-free survival.
- Diarrhea was the most common adverse event, but no severe cases were observed.

## Abstract

Data from multiple clinical trials have shown that pyrotinib has demonstrated significant efficacy and acceptable tolerability in patients with HER2-positive advanced breast cancer (BC). However, the short time to market in China limits our comprehensive understanding of the drug’s long-term efficacy and potential adverse events (AEs) from the drug. Therefore, this study analyzed the clinical efficacy and safety of pyrotinib-based regimens in a real-world database.

This study retrospectively analyzed patients with HER2-positive stage III/IV BC who were treated with pyrotinib-based regimens from October 2018 to October 2022 at the Affiliated Tumor Hospital of Guangxi Medical University. Tumor assessments were based on RECIST 1.1, and AEs were assessed and graded according to NCI-CTCAE 5.0. Long-term efficacy was evaluated by calculating median progression-free survival (mPFS, defined as the time from treatment initiation until disease progression or death).

Of the 37 included patients, the objective response rate (ORR) was 62.2%, the disease control rate (DCR) was 94.6%, and the median progression-free survival length was 12.0 months (95% CI [5.8 ∼18.2] months). A subgroups comparison found that significant differences were observed in patients who had not used lapatinib (P = 0.016), had a number of metastatic sites ≤ 2 (P = 0.011), were intolerant to trastuzumab (P = 0.004), and were on first-line pyrotinib treatment (P = 0.036), with these patients having median progression-free survival lengths of 13.0 months, 15.9 months, 23.5 months, and 23.5 months, respectively. Pyrotinib was also effective in patients with advanced brain metastases after multiple lines of complex therapy, with these patients having a median progression-free survival length of 5.0 months. Diarrhea was the most common adverse event (97.3%), with no grade 4 AEs observed. This study was the first to compare the relationship between different degrees of diarrhea and mPFS, and no significant differences in mPFS were observed (P = 0.291). In addition, a rare positive fecal occult blood profile (5.4%) was observed.

Pyrotinib-based regimens have shown satisfactory clinical efficacy in HER2-positive stage III/IV BC patients, and pyrotinib is well tolerated with manageable adverse events.