The estrogen receptor coactivator AIB1 is a new putative prognostic biomarker in ER positive/HER2 negative invasive lobular carcinoma of the breast
PurposeAccording to the 2017 St Gallen surrogate definitions of the intrinsic subtypes, Ki67, progesterone receptor (PR) and Nottingham histological grade (NHG) are used for prognostic classification of estrogen receptor (ER) positive/HER2 negative breast cancer into luminal A or luminal B like. The aim of the present study was to investigate if additional biomarkers, related to endocrine signaling pathways, e.g. amplified in breast cancer 1 (AIB1) androgen receptor (AR) and G protein coupled estrogen receptor (GPER) can provide complementary prognostic information in a subset of ER positive/HER negative invasive lobular carcinoma (ILC).MethodsBiomarkers from 224 patients were analyzed immunohistochemically on tissue microarray. The primary endpoint was breast cancer mortality (BCM) analyzed with 10 and 25 year follow up (FU) In addition, the prognostic value of gene expression data for these biomarkers was analyzed in three publicly available ILC datasets.ResultsAIB1 (high vs. low) was associated to BCM in multivariable analysis (adjusted for age, tumor size, nodal status, NHG, Ki67, luminal like classification, and adjuvant systemic therapy) with 10 year FU (HR 6.8, 95% CI 2.3 20, P 0.001) and 25 year FU (HR 3.0, 95% CI 1.1 7.8, P 0.03) The evidence of a prognostic effect of AIB1 could be confirmed by linking gene expression data to outcome in independent publicly available ILC datasets. AR and GPER were neither associated to BCM with 10 year nor with 25 year FU (P 0.33) Furthermore, Ki67 and NHG were prognostic for BCM at both 10 year and 25 year FU, whereas PR was not.ConclusionsAIB1 is a new putative prognostic biomarker in ER positive/HER2 negative ILC.
Breast Cancer Research and Treatment