Evaluation of the analytical performance of the Breast Cancer Index (BCI) assay.

540Background: BCI is an 11-gene RT-PCR based assay that predicts risk of overall (0-10y) and late ( > 5y) distant recurrence, and is predictive of extended endocrine benefit in patients with early-stage, ER+ breast cancer. The objective of the current study was to evaluate the analytical performance characteristics of the BCI assay. Methods: Studies were conducted using primary resected formalin-fixed paraffin-embedded breast tumor samples. Repeatability, reproducibility, and RNA input range were assessed, and PCR linearity studies for each gene were performed. Total standard deviation (SD) was calculated as the sum of between-subject and within-subject variability estimated by linear mixed models. Assay interference studies included tumor specimens combined with patient-matched, non-tumor elements: normal tissue, activated stroma and inflammatory cells. Assay success rate due to specimen age was examined on consecutive clinical cases (N = 2667). Receiver Operating Characteristic (ROC) analysis was perfo...