Given the lack of data on CIPN associated with eribulin as first- or second-line therapy in patients with breast cancer, we conducted a 2-year post-marketing observational study to assess CIPN incidence by severity and the risk factors for CIPN in patients with HER2-negative inoperable or recurrent breast cancer treated with eribulin, regardless of the patient’s line therapy status. Here, ERBB2 is linked to breast carcinoma.