Using the PAM50 breast cancer intrinsic classifier to assess risk in ER+ breast cancers: A direct comparison to Oncotype DX.

503 Background: Multianalyte gene expression assays have proven valuable in the management of breast cancer, however, the methodologies and indications for these assays can differ. In ER+ breast cancer, there continues to be debate about the most important components of these tests for determining risk of relapse. The PAM50 test has genes relevant to ER+ and ER− disease, while the Oncotype Dx recurrence score (RS) was tailored specifically for ER+ breast cancer. The components of the PAM50 that are most relevant to the RS are assessed. Methods: A total of 151 ER+ breast cancers, that were sent to Genomic Health Inc for Oncotype Dx testing from the University of Texas M. D. Anderson Cancer Center at the time of diagnosis (2004-2008), were re-analyzed at ARUP Laboratories Inc using the PAM50 Breast Cancer Intrinsic Classifier. Formalin-fixed, paraffin-embedded tissue blocks containing invasive breast carcinoma were selected after H&E review by a pathologist. RNA was extracted from full face scrolls and dire...