Introduction

Breast cancer has become the most commonly diagnosed cancer globally in 2020, surpassing lung cancer (11.4%), with an estimated 2,261,419 new cases (11.7%), and the fourth leading cause (6.9%) of cancer-related deaths worldwide, with an estimated 684,996 new deaths in 2020 [1]. Approximately 20–50% of patients with early breast cancer will eventually develop metastatic disease [2], and 5–10% of patients are initially diagnosed with metastatic disease [3]. Among patients with metastatic breast cancer (MBC), 62% are diagnosed with human epidermal growth factor receptor 2 (HER2)-negative disease [4]. Despite considerable advances in new treatments, MBC remains treatable but incurable, with the goal of treatment to prolong patients’ survival and improve their quality of life [5, 6].

During the past 70 years, the highest number of new drugs for breast cancer was approved [7]. Nevertheless, conventional anthracyclines (doxorubicin and epirubicin) and taxanes remain the cornerstones of breast cancer therapy regardless of the molecular subtype, whether in the neoadjuvant/adjuvant setting or metastatic setting[6, 8,39, 43].

This study had several limitations. First, this study had a single-center, open-label design with no control arm. Second, the implementation of the study took longer than originally planned. The slow enrollment of patients was aggravated by the COVID-19 pandemic. Third, this was an exploratory trial with small sample sizes.

Conclusion

In summary, our study demonstrated that PLD (Duomeisu®) monotherapy at 40 mg/m2 every 4 weeks was effective and safe in patients with HER2-negative MBC heavily pretreated with conventional anthracycline and taxanes, indicating that this treatment is a viable treatment option for this population.