Association of human epidermal growth factor receptor 2 status with ipsilateral breast tumor recurrence and resistance to endocrine therapy.

The effect of prior endocrine therapy on tumor biology and clinical outcomes of locoregional recurrence remains unclear. A total of 76 patients, who underwent salvage breast surgery for estrogen receptor-positive ipsilateral breast tumor recurrence (IBTR) following breast-conserving surgery for primary breast cancer, were retrospectively reviewed to investigate the association of human epidermal growth factor receptor 2 (HER2) status with the characteristics of IBTR and clinical outcomes following resection of IBTR. There was a tendency for more patients with HER2-positive IBTR to show resistance to endocrine therapy (71.4%) compared with those with HER2-negative IBTR (37.3%) (P=0.085). Patients with HER2-positive IBTR exhibited a higher rate of recurrence (62.5%) compared with those with HER2-negative IBTR (25.0%) (P=0.027). These results suggested that HER2-positive IBTR may be associated with resistance to endocrine therapy and a poorer clinical outcome.