Predictive and prognostic value of ER-α36 expression in breast cancer patients treated with chemotherapy

Background: This study is to investigate the predictive and prognostic value of ER-α36 expression in breast cancer patients treated with chemotherapy.

Methods: ER-α36 expression in 120 breast cancer tumors was assessed by an immunohistochemistry assay. All patients were divided into two groups according to the chemotherapy procedure: group A, 50 patients who underwent neoadjuvant chemotherapy before surgery; group B, 70 patients who were performed adjuvant chemotherapy after surgery, and they all took at least two cycles of anthracycline-based and/or paclitaxel-based chemotherapy after surgery. The therapy effect on group A patients was evaluated two cycles later by Response Evaluation Criteria in Solid Tumors version 1.0 (RECIST 1.0).

Results: ER-α36 protein was positively expressed in 51 tumor specimens (42.5%) and no correlation was found between the expression of ER-α 36 and the expression of the full-length ER-α (ER-α66), progesterone receptor (PgR), human epidermal growth factor receptor 2 (HER-2), Ki-67, tumor sizes, and the numbers of lymph node metastasis. Patients with ER-α36 negative expression tumors treated with the neoadjuvant chemotherapy had a higher remission rate [partial response: stable: progressed (n) 25:3:1 vs.11:9:1; P=0.009], a better response (86% vs. 52%; P=0.009), and a more favorable outcomes in triple-negative breast cancer patients compared to ER-α36 positive patients and ER-α36 negative expression was correlated with DFS in patients treated with neoadjuvant chemotherapy.

Conclusions: ER-α36 negative tumors benefit more from neoadjuvant chemotherapy and have better prognosis, which may warrant further studies with larger size of the sample.