Differences in clinical outcomes between HER2-negative and HER2-positive luminal B breast cancer

The clinical features and prognosis of breast cancer can vary widely, depending on the molecular subtype. Luminal B breast cancers are usually either estrogen receptor-positive and/or progesterone receptor-positive with high proliferation of Ki67 index, or HER2 positive (HER2+). The authors compared the clinicopathologic factors and survival rates of different subtypes of luminal B breast cancer according to HER2 status. Between 2009 and 2013, 1131 cases of breast cancer were reviewed and characterized as 1 of 4 different molecular subtypes based on their immunohistochemical results: luminal A, luminal B, HER2+, or triple-negative breast cancer. From these, luminal B breast cancers were extracted and the clinical features and prognosis of the HER2- and the HER2 + subtypes were compared. Survival differed significantly based on the molecular subtype regardless of whether or not the patient received treatment with neoadjuvant chemotherapy. While patients with HER2- luminal B breast cancer who received neoadjuvant chemotherapy had better prognoses, patients with HER2 + luminal B breast cancer who did not receive neoadjuvant chemotherapy had better prognoses. Luminal B breast cancers showed different clinical outcomes and survival rates according to HER2 gene overexpression type. Physicians should consider these results when they establish a treatment strategy.