Original ArticlesEndoPredict predicts for the response to neoadjuvant chemotherapy in ER-positive, HER2-negative breast cancer
Introduction
During the last decade, the survival of patients with breast cancer improved thanks to mass screening and adjuvant systemic therapy. A crucial issue regarding adjuvant chemotherapy is to improve the prognostic features to avoid overtreatment of patients – notably those without or less than four pathologically involved axillary lymph nodes – who receive post-operative chemotherapy but would be cured by surgery and radiotherapy alone. That is particularly critical for patients with oestrogen receptor-positive (ER+)/HER2– tumour, who represent the largest subset of early breast cancer patients. Indeed, if adjuvant chemotherapy is currently recommended for most women with HER2+ tumours or with triple-negative tumours [1], its indications are much more challenging in patients with ER+/HER2– tumours that are either candidate for adjuvant hormone therapy alone or for both hormone therapy and chemotherapy.
During the last decade, gene expression profiling identified promising prognostic multigene signatures in breast cancer [2]. In the setting of ER+/HER2– tumours, several signatures including Mammaprint [3], Recurrence Score [4], or EndoPredict [5] have been proposed to improve the selection of patients candidate or not to adjuvant chemotherapy [1]. They were developed in heterogeneous cohorts of patients with respect to ER and HER2 status, except EndoPredict (EP), which was specifically developed in ER+/HER2– node-negative/positive tumours [5]. EP is based on mRNA expression of 8 genes of interest and 3 reference genes measured using quantitative RT-PCR on formalin-fixed paraffin-embedded (FFPE) samples. In contrast with Mammaprint and Recurrence Score, EP is suitable for decentralised testing in molecular pathology laboratories instead of a single reference laboratory [6]. EP independent prognostic value was first validated in a series of 1702 independent tumours from two prospective trials of adjuvant hormone therapy. EP segregated patients into two groups according to their distant relapse risk: for example, in the ABCSG-8 prospective trial, the distant recurrence rate was 6% in the low-risk group and 15% in the high-risk group, suggesting that low-risk patients could be treated with adjuvant hormone therapy without any chemotherapy 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. This has already been shown with other signatures such as Recurrence Score [7], Mammaprint [8] and Genomic Grade Index [9]. We thus hypothesised that patients with breast cancer classified as high-risk of relapse according to EP would respond better to chemotherapy.
To prove this issue, we retrospectively analysed the predictive value of EP signature in terms of pathological response to chemotherapy in a large pooled series of breast cancer patients treated with anthracycline-based neo-adjuvant chemotherapy and whose tumour had been previously profiled using DNA microarrays. We show that the EP signature is associated with response to chemotherapy.
Section snippets
Patients' selection
We collected seven retrospective gene expression data sets of breast cancer samples profiled using DNA microarrays (Supplementary Table S1), including our own set [10] and six public sets [11], [12], [13], [14], [15], [16]. Gene expression and histoclinical data were retrieved from the NCBI GEO database and authors' website. Selection criteria of data sets were the presence of at least 10 profiled samples representing pre-treatment invasive breast carcinoma, treated with anthracycline-based
Patients' characteristics
We collected personal and public gene expression and histoclinical data of 553 pre-treatment ER+/HER2– invasive breast carcinomas with available pathological response assessed on the surgical specimen after anthracycline-based neoadjuvant chemotherapy. Their characteristics are summarised in Table 1. Median age of patients was 49 years. Clinically, the tumours were classified T2–T4 in 93%, and the axillary lymph node status was positive in 65% of patients. Most tumours were ductal type and SBR
Discussion
We searched for correlations between the EP classification and the response to chemotherapy in ER+/HER2– breast cancer. Through a retrospective analysis of gene expression data of 553 pre-treatment samples, we show that tumours with an EP high-risk score are associated with higher pCR rate to chemotherapy than tumours with a low-risk score. To our knowledge, this is the first demonstration of correlation between the EP signature and the response to chemotherapy.
The EP signature was developed as
Conflict of interest
The authors declare that they have no conflict of interest.
Acknowledgments
Our work is supported by Institut Paoli-Calmettes, Inserm, Institut National du Cancer (AOPL2010 IVOIRES), Ligue Nationale contre le Cancer (label DB) and SIRIC INCa-DGOS-Inserm 6038.
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