Biology and prognosis of HER2-negative breast cancer with low-ER and PgR-expressions.

Abstract

e12020 Background: Expression of the estrogen (ER) and progesterone receptor (PgR) is still clinically important in predicting prognosis and determining therapeutic strategies in breast cancer. According to the ASCO and CAP guidelines tumors with ≥1% positively staining cells should be considered ER/PgR positive. The clinical significance of low-ER/PgR-staining (1-9%) tumors were analyzed to investigate the biology and prognosis. Methods: This study examined 3193 consecutive HER2 negative invasive breast cancer cases. Clinicopathological characteristics and prognosis of hormone receptor (HR)-negative (<1%), low-HR-staining (1-9%) tumors and positive (≥ 10%) tumors were compared. The median follow-up period was 75 months. Results: The following is the number of patients in each of the tumor categories: 466 ER cases (14.6%) and 775 PgR cases (24.2%) in the <1% group; 68 ER cases (2.1%) and 218 PgR cases (6.8%) in the 1-9% group; and 2559 ER cases and 2200 PgR cases in the ≥ 10% group. The age groups were; young (≤35 y), premenopausal (36-50 y), postmenopausal (51-65 y) and the elderly (≥66 y). The median ER positive cell rate was significantly lower in the young group. In contrast, the PgR expression was significantly higher in the premenopausal group and significantly lower in the postmenopausal group. Patients in the ≥10% group had significantly smaller tumors, lower Ki-67 values, a lower p53 overexpression and nuclear grade. The elderly group had better disease-free survival (DFS) and the young group had the lowest DFS. In addition, DFS by ER/PgR expression was more favorable in the ≥ 10% group than the other groups. Patients with 1-9% ER had significantly lower DFS than those in the ≥10% elderly group. Patients with 1-9% PgR had significantly lower DFS than those in all the ≥10% groups and significantly lower DFS than those in the <1% premenopausal group. Multivariate analysis for DFS revealed that PgR expression, lymph node metastasis and tumor size were significant prognostic factors. Conclusions: There was a clear difference in the PgR expression rate due to the menopausal status. Moreover, the 1-9% ER and PgR groups had biological features that were similar to ER/PgR-negative tumors.