EndoPredict Predicts for the Response to Neoadjuvant Chemotherapy in ER-positive, HER2-negative Breast Cancer

The EndoPredict (EP) signature is a prognostic 11-gene expression signature specifically developed in ER+/HER2- node-negative/positive breast cancer. It is associated with relapse-free survival in patients treated with adjuvant hormone therapy, suggesting that EP low-risk patients could be treated with adjuvant hormone therapy alone whereas high-risk patients would deserve addition of adjuvant chemotherapy. Thus, it is important to determine whether EP high-risk patients are or are not more sensitive to chemotherapy than low-risk patients. Here, we have assessed the EP predictive value for pathological complete response to neoadjuvant chemotherapy in ER+/HER2- breast cancer. We gathered gene expression and histoclinical data of 553 pre-treatment ER+/HER2- breast carcinomas treated with anthracycline-based neoadjuvant chemotherapy. We searched for correlation between the pathological complete response (pCR) and the EP score-based classification. The overall pCR rate was 12%. Fifty-one percent of samples were classified as low-risk according to the EP score and 49% as high-risk. EP classification was associated with a pCR rate of 7% in the low-risk group and 17% in the high-risk group (p < 0.001). In multivariate analysis, the EP score remained significantly associated with pCR. Many genes upregulated in the high-risk tumours were involved in cell proliferation, whereas many genes upregulated in the low-risk tumours were involved in ER-signalling and stroma. Despite higher chemosensitivity, the high-risk group was associated with worse disease-free survival. In conclusion, EP high-risk ER+/HER2- breast cancers are more likely to respond to anthracycline-based chemotherapy.