Impact of the EndoPredict-clin score on risk stratification in ER-positive, HER2-negative breast cancer after considering clinical guidelines.

Abstract

542 Background: Many ER-positive, HER2-negative breast cancer patients are treated by adjuvant chemotherapy according to current clinical guidelines. We retrospectively assessed whether the combined gene expression/ clinicopathological EndoPredict-clin (EPclin) score improved the accuracy of risk classification in addition to considering clinical guidelines. Methods: Three clinical breast cancer guidelines (National Comprehensive Cancer Center Network (NCCN), German S3 and St. Gallen 2011), and the EPclin score - assessed by quantitative RT-PCR in formalin-fixed paraffin-embedded tissue - were used to assign risk groups in 1,702 ER-positive, HER2-negative breast cancer patients from two randomized phase III trials (Austrian Breast and Colorectal Cancer Study Group 6 and 8) treated with endocrine therapy only. Results: Although all analyzed clinical guidelines identified a low-risk group with improved metastasis-free survival, the overwhelming majority of all patients (81-94%) were classified as intermediate / high risk. In contrast to that, the EPclin classified only 37% of all patients as high risk and that stratification resulted in the best separation between low and high risk groups (p < 0.001, HR = 5.11 (3.48-7.51). Consequently, the majority of all patients deemed intermediate / high risk by the clinical guidelines was re-classified as low risk by the EPclin score. Kaplan Meier analyses demonstrated that the re-classified subgroups (47 to 57% of all patients) had an excellent 10-year metastasis-free survival of 95% comparable to the clinical assigned low-risk groups although encompassing a higher proportion of the trial patients. Conclusions: The EPclin score predicted distant recurrence more accurately than all three clinical guidelines and is especially useful to reclassify patients considered as intermediate / high risk by the guidelines. The data suggests that the EPclin score provides clinically useful prognostic information beyond common clinical guidelines and can be used to accurately identify the clinically relevant group of patients who are adequately and sufficiently treated with adjuvant endocrine therapy alone.