# Real-world treatment patterns and clinical outcomes in patients treated with eribulin after prior phosphoinositide 3-Kinase inhibitor treatment for metastatic breast cancer

## TL;DR

This study examines how patients with breast cancer responded to eribulin after failing a PI3K inhibitor, showing promising survival outcomes.

## Contribution

The study provides real-world evidence of eribulin's effectiveness after PI3K inhibitor failure in metastatic breast cancer.

## Key findings

- Eribulin was often used in the second or third line of treatment for metastatic breast cancer.
- The median real-world progression-free survival was 18.9 months, and 82.6% of patients were alive at 12 months.
- 72% of patients had a complete or partial response to eribulin treatment.

## Abstract

In 2010, the US Food and Drug Administration approved eribulin for the treatment of metastatic breast cancer (MBC). Since then, the treatment landscape has evolved with many new therapy classes, a more recent one being the small molecule inhibitors of phosphoinositide 3 kinase (PI3K). We sought to characterize the treatment patterns and clinical outcomes of patients with MBC who received eribulin following prior treatment with a PI3K inhibitor.

A retrospective cohort study based on medical record review included MBC patients who initiated eribulin between March 2019 and September 2020 following prior treatment with a PI3K inhibitor was conducted. Patient demographics, treatment characteristics, and clinical outcomes were analyzed descriptively. Real-world progression-free survival (rwPFS) and overall survival (OS) were estimated from the initiation of eribulin therapy using Kaplan-Meier analyses.

82 eligible patients were included. Patients’ median age at eribulin initiation was 62 years; 86.5% had hormone receptor–positive, human epidermal growth factor receptor 2–negative tumors. Eribulin was most often administered in the second or third line (82.9%) in the metastatic setting. Best overall response on eribulin was reported as complete or partial response in 72% of the patients. The median rwPFS was 18.9 months (95% confidence interval [CI], 12.4-not estimable); median OS was not reached. The estimated rwPFS and OS rates at 12 months were 63.3% (95% CI, 50.5–73.7) and 82.6% (95% CI, 72.4–89.3), respectively.

Our real-world study suggests that eribulin may be a potential treatment option for MBC patients who fail a prior PI3K inhibitor.