Abstract P3-10-33: Mammostrat® as an Immunohistochemical Multigene Assay for Prediction of Early Relapse Risk in Postmenopausal Early Breast Cancer: Preliminary Data of the TEAM Pathology Study

Abstract

Abstract Background: Postmenopausal early breast cancer patients, treated with endocrine therapy, have approximately 90% five year disease free survival (DFS). However, for patients at higher risk of relapse, additional adjuvant chemotherapy may be indicated. The challenge is to prospectively identify such patients. The Mammostrat test uses five immunohistochemical markers to stratify patients on tamoxifen (T) therapy into various risk groups potentially guiding treatment choices. We tested the efficacy of this panel in the TEAM trial (exemestane (E) versus T→E) to determine the relevance in patients treated with an AI. Patients & Methods: Pathology blocks from 4598 TEAM patients were collected and tissue microarrays constructed. The cohort overall was 47% node positive, and 36% also received adjuvant chemotherapy. Samples were stained, using triplicate 0.6mm2 TMA cores, and positivity for p53, HTF9C, CEACAM5, NDRG1, SLC7A5 assessed. Each case was assigned a Mammostrat risk score and analysed for disease free survival (DFS) by marker positivity and risk score. Results: Preliminary results on the UK TEAM cohort (1059 cases) showed 18.9% stained positive for p53 (184/972), 21.3% for NRDG1 (204/956), 26.4% for SLC7A (253/957), 21.9% for HTF9C (220/1004), 18.3% for CEACAM5 (185/1009). Complete data was available for 919 cases including patients treated with chemotherapy, with 447 (49%) designated low risk, 213 (23%) medium and 259 (28%) high risk. In univariate analysis, Mammostrat scores were prognostic (p=0.02), with 5 year DFS (see comment above) results being 86.9±1.7%, 80.1±3.0% and 80.8±2.6% for patients with low, medium and high Mammostrat scores respectively. Analyses on the entire TEAM pathology cohort are ongoing, and further data with sufficient power to evaluate the impact of Mammostrat in multivariate regression analyses will be presented. Conclusion: Preliminary analysis of the impact of the Mammostrat score in both tamoxifen and exemestane treated patients suggests it retains its prognostic value in this context. Further analysis with the power to evaluate the impact of Mammostrat in multivariate regression analyses will be presented. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-33.