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

ABSTRACT

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.