Characteristics and prognosis of young breast cancer patients with low expression of estrogen receptor

To evaluate the clinical characteristics and prognosis of young breast cancer patients with an ER of 1%-10%. Breast cancer patients aged <= 35 years old were selected and classified into three groups, ER-negative group, ER-low positive group (ER positivity: 1%-10%) and ER-high positive group (ER positivity: >= 10%), to compare their clinicopathological characteristics and prognosis. Of the 1387 patients assessed, 30.4% were ER-negative, 4.3% were ER-low positive, and 65.3% were ER-high positive. There was no difference in age, Tumor Node Metastasis (TNM) stage, histological type, adjuvant chemotherapy and adjuvant radiation therapy among the three groups (p > 0.05). A higher histological grade and greater Human Epidermal Growth Factor Receptor-2 (HER-2) positivity were observed in the ER-low positive group than in the ER-high positive group (p < 0.001). The number of patients with Progesterone Receptor (PR) negative in the ER-low positive group was between the other two groups. The recurrence rate of breast cancer in the ER-low positive group was 27.1%, which was similar to that of the ER-negative group (28%; p > 0.05) but higher than the ER-high positive group (21.4%; p = 0.03). After a median follow-up of 74 months, the ERhigh positive group had the longest Disease Free Survival (DFS) compared with the ERnegative group (p < 0.0001) and ER-low positive group (p < 0.05), while there was no significant difference in DFS between the latter two groups (p = 0.73). Similarly, the ERhigh positive group had the longest Overall Survival (OS) than the ER-negative group (p < 0.0001) and the ER-low positive group (p < 0.05), while there was no statistical difference in OS between the latter two groups (p = 0.77). After endocrine therapy, no improvement in DFS (p = 0.71) and OS (p = 0.54) was observed in the ER-low positive group. In young breast cancer patients, the clinicopathological characteristics of the ERlow positive group were different from the ER-high positive group but were more similar to the ER-negative group. The DFS and OS were shorter than the ER-high group, and despite receiving endocrine therapy, DFS and OS of the ER-low positive group were not significantly prolonged.