Abstract P2-10-02: Clinical validation of the PAM50 risk of recurrence (ROR) score for predicting residual risk of distant-recurrence (DR) after endocrine therapy in postmenopausal women with ER+ early breast cancer (EBC): An ABCSG study

Abstract

Abstract Aim: To assess the performance of the ROR score in predicting DR for postmenopausal patients with ER+ EBC treated with tamoxifen or tamoxifen followed by anastrozole when the PAM50 test is performed in a routine hospital pathology laboratory. Background: The multi-analyte gene-expression tests (Oncotype DX, MammaPrint) that are currently used in clinical practice to assess prognosis after endocrine therapy in primary ER+ breast cancer are performed in a central referral laboratory. PAM50 is a 50-gene test in development that is designed to be performed in local routine hospital pathology laboratories and has been optimized to separate intrinsic disease subtypes which are used to generate a ROR score. This ROR score has been clinically validated and demonstrated to contain more prognostic information than Oncotype Dx RS in the TransATAC patient population (Dowsett, SABCS, 2011). Methods: 1,251 women from the prospective randomized ABCSG-8 trial were entered into this study: the entry criteria were the availability of their FPET block and informed consent. Three unstained 10 micron sections and 1 H&E slide for each patient were sent to an independent academic pathology laboratory at BCCA where tissue review, manual micro-dissection and RNA extraction were performed. PAM50 analysis was then conducted on 250 ng of the extracted RNA using the NanoString nCounter® technology: both intrinsic subtype and ROR score were calculated. The median follow up of the patients entered into this study is 10 years. 912 are node negative and 339 are node positive. The baseline characteristics of the patients entered showed them to be a representative sample of the overall ABCSG-8 trial population. The primary analysis is designed to test whether the continuous ROR score adds prognostic value over and above the standard clinical variables, using a likelihood ratio test. Results: Results are currently being derived and will be presented in full at SABCS. Discussion: This large clinical trial serves both as a clinical validation study of the PAM 50 test and as a demonstration that a complex multi-analyte gene-expression test can be performed in a routine hospital pathology laboratory while meeting the same quality metrics as a central referral laboratory. The results of the primary analysis, when combined with the results already reported from the Trans ATAC population, yield Level 1 evidence for clinical validity of the PAM50 test for predicting the risk of DR in postmenopausal women with ER+ EBC and form the basis of the design of the clinical utility studies of the PAM 50 test. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-02.