Background: There is little information about the impact of breast cancer subtype on prognosis after ipsilateral breast tumor recurrence (IBTR). Methods: One hundred eighty-five patients were classified according to breast cancer subtype, as approximated by estrogen receptor, human epidermal growth factor receptor 2 (HER2), and Ki-67, of IBTR, and we evaluated whether breast cancer subtype was associated with distant recurrence after IBTR. Results: There was a significant difference in distant disease-free survival (DDFS) after IBTR according to breast cancer subtype defined by a cutoff of the Ki-67 index of 20 % (p = 0.0074, log-rank test). The 5-year DDFS rates for patients with luminal A, luminal B, triple-negative, and HER2 types were 86.3, 57.1, 56.6, and 65.9 %, respectively. In addition, breast cancer subtype was significantly associated with distant recurrence after IBTR on adjustment for various clinicopathologic factors (p = 0.0027, Cox proportional hazards model). Conclusions: Our study suggests that breast cancer subtype based on immunohistochemical staining predicts the outcomes of patients with IBTR. Further analyses are needed (UMIN-CTR number UMIN000008136).
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