Prognostic Value of Estrogen and Progesterone Receptor Expression in Low Proliferative Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer

ABSTRACT

PURPOSE: Approximately two-thirds of breast cancer are estrogen-dependent cancers, which express estrogen receptor (ER)/progesterone receptor (PR). We investigated the prognostic value of ER/PR expression in human epidermal growth factor receptor 2 (HER2)-negative and low proliferative (Ki-67 ≤20%) breast cancer. METHODS: A retrospective review was performed of 252 breast cancer data records, identified as ER/PR-positive, low Ki-67 proliferation index (≤20%) and HER2-negative. The data were divided into two subgroups a strong luminal subgroup and a weak luminal subgroup, according to hormonal receptor expression status. Outcome measures included age at diagnosis, tumor size, tumor-node-metastasis (TNM) stage, ER, PR, Bcl-2, recurrent or metastatic characteristics, disease-free survival and overall survival, of each subgroup. RESULTS: There were no statistical differences in TNM stage or tumor numbers between the two subgroups. The strong luminal subgroup was associated with a higher Bcl-2 expression (p<0.001). The weak luminal subgroup was associated with more frequent neural invasion (p=0.051) and lung (p=0.031), liver (p=0.031) and brain (p=0.033) metastases, than the strong luminal subgroup. Disease-free survival was significantly longer in the strong luminal subgroup than weak luminal subgroup (p=0.015). Overall survival was also significantly improved in the strong luminal subgroup relative to the weak luminal subgroup (p=0.014). CONCLUSION: The weak luminal subgroup showed worse prognosis than the strong luminal subgroup, among ER/PR-positive HER2-negative low proliferative breast cancer patients. Weak ER or PR expression, can be considered a poor prognostic factor in ER/PR-positive HER2-negative low proliferative breast cancer.