Predicting the Efficacy of Eribulin in Metastatic Breast Cancer by Assessing E-Cadherin and Vimentin Expression

Eribulin, a microtubule inhibitor, is effective as later-line therapy for metastatic breast cancer (MBC) and has been reported to remodel the tumor microenvironment and inhibit epithelial-mesenchymal transition (EMT). However, the association between pretreatment EMT status and eribulin efficacy remains unclear. We retrospectively analyzed 41 patients with MBC (excluding invasive lobular carcinoma) treated with eribulin between 2013 and 2020. Formalin-fixed, paraffin-embedded biopsy specimens were examined by immunohistochemistry (IHC) using anti-E-cadherin (24E10) and anti-vimentin (V9) antibodies. Complete membranous E-cadherin expression (3+) was defined as normal; reduced expression (2+, 1+, 0) as altered. Negative vimentin was considered normal; positive expression, altered. Co-localization of E-cadherin and vimentin was assessed by multi-immunofluorescent staining. Of the 41 patients, 24 responded to eribulin and 17 did not. Progression-free survival (PFS) and overall survival (OS) were significantly longer in responders than in nonresponders (<i>p</i> < 0.001 and <i>p</i> = 0.0044). Altered E-cadherin and/or vimentin expression was more frequently observed in responders (<i>p</i> = 0.013) and associated with longer progression-free survival (<i>p</i> = 0.048). These results suggest that eribulin efficacy may be predicted by altered E-cadherin and vimentin expression before treatment.