Clinicopathological and prognostic features of HER2-null and HER2-low advanced breast cancer treated with eribulin or capecitabine

HER2-low populations constitute a heterogeneous group, and the cytotoxic anticancer agent efficacy based on HER2 status remains unclear. This study evaluated the clinicopathological features and outcomes of patients with advanced breast cancer showing HER2-low expression treated with eribulin or capecitabine, two treatment options after anthracycline and taxane treatment.

We retrospectively evaluated patients who were treated with eribulin or capecitabine between 2011 and 2015. HER2 status was evaluated according to the ASCO/CAP guidelines.

No significant difference was observed in overall survival (OS; eribulin: hazard ratio [HR], 0.66; 95% CI 0.40–1.10; capecitabine: HR, 0.76; 95% CI 0.45–1.30) or progression-free survival (PFS; eribulin: HR, 1.13; 95% CI 0.72–1.78; capecitabine: HR, 0.90; 95% CI 0.56–1.44) between patients receiving eribulin (HER2-null: 35, HER2-low: 44) and those receiving capecitabine (HER2-null: 41, HER2-low: 33). Subgroup analysis revealed no significant differences in OS between the two groups in the hormone-positive and -negative populations for eribulin and capecitabine. HER2-null and HER2-low patients showed objective response rates (ORRs) of 22.5% and 9.1% (p = 0.09) overall, and 32.0% and 10.5% (p = 0.03), respectively, in hormone-positive cases among eribulin-treated patients. No response was observed in hormone-negative patients. Capecitabine treatment in HER2-null and HER2-low patients had overall ORRs of 26.8% and 15.2% (p = 0.23), respectively, with 27.3% and 16.1% (p = 0.28) for hormone-positive cases; and 25.0% and 0% (p = 1.0), respectively, for hormone-negative cases.

Eribulin and capecitabine sensitivity may vary based on HER2 expression in patients with HER2-low and HER2-null breast cancer. Prognosis was similar between the HER2-low and the HER2-null groups.