Abstract P6-09-27: The EA2clin test significantly predicts response and survival in both pre and post-menopausal women with ER-positive breast cancers

Abstract

Abstract Background Identifying breast cancer (BC) patients likely to recur on endocrine therapy (ET) is a challenge. Several methods and tests based on clinical parameters and multi-gene or protein classifiers have been shown to predict those likely to recur. Tests that incorporate baseline and on-treatment markers are likely to be more accurate than tests based on baseline characteristics alone. 4 genes were identified by microarray that predicted for to ET: 2 at diagnosis and 2 at 14 days. The EndoAdjuvant2 (EA2) test uses 2 of these genes: IL6ST at diagnosis and on-treatment MCM4 at transcript level or by graded immunohistochemistry (IHC). The aim of this study was to compare EA2 with currently used clinical parameters in 4 different cohorts of pre and postmenopausal women. Patients The cohorts are (1) 73 post-menopausal women (PMW) with ER+ BC treated with neoadjuvant letrozole (L) then surgery, (2) 39 PMW with ER+ BC treated with neoadjuvant anastrozole (A) then surgery, (3) 108 PMW who received 2-weeks of A or L prior to surgery (4) 25 preMW with ER+ BC who received one 750mg dose of fulvestrant prior to surgery. All had adjuvant ET and 5-10 years follow up. Neoadjuvant response was assessed by periodic 3D ultrasound. Results The 4 gene assay had 96% (training; cohort 1) and 93% (validation; cohort 2) accuracy of response prediction to neoadjuvant L or A. In cohort 1, clinical parameters were available. On univariate regression analysis intrinsic subtype (luminal A/B; defined using PAM50) (P=0.002), histological grade (P=0.033) and HER2 status (P=0.001) significantly predicted clinical response. EA2 out-performed all these in both univariate (P<0.0001) and multivariate regression analysis (P<0.0001). The final model only retained EA2 as significant. Node status, tumour size and PR expression were not associated with response to endocrine therapy. EA2 predicted recurrence free in cohorts 1 and 3 combined: RFS (P=0.0004, HR=17.63 95%CI: 4.95-17.6), BCSS (P=0.0007, HR=16.60: 3.36-45.7). The Nottingham Prognostic Index (NPI) also predicted RFS (P=0.0002) and BCSS (P=0.0017) in univariate analysis but in the Cox analysis NPI was not found to be significant, although in the low risk group there were only 1/46 events compared to 19/62 in the moderate/high risk group. Histological grade (P<0.0001), Ki67 (%) (P=0.02) and tumour size (P=0.007) were significant on univariate analysis. In the Cox regression analysis, only EA2 (P=0.012) and histological grade (P=0.016) were significant predictors of RFS and BCSS. Using EA2 and NPI together a high and low risk subgroup could be identified. In the Cox regression analysis, combined EA2 plus NPI (EA2clin) outperformed both NPI and EA2 alone. EA2clin was validated in cohort 4 and predicted RFS (P=0.002, HR=8.43 95%CI: 2.18-32.53) and BCSS (P=0.008, HR=10.95 95%CI: 1.48-64.9). Conclusions • EA2 predicts clinical response, RFS and BCSS • EA2clin combines NPI and EA2, outperforms either alone and predicts outcome in a new validation cohort of preMW treated with Fulvestrant • EA2clin works in preM and PM women regardless of ET. Citation Format: Turnbull AK, Pearce DA, Arthur LM, Martinez-Perez C, Thomas JS, Fernando A, Renshaw L, Sims AH, Dixon JM. The EA2clin test significantly predicts response and survival in both pre and post-menopausal women with ER-positive breast cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-09-27.