Many genomic assays that assess recurrence risk in EBC are prognostic, but they differ in risk group stratification, which can affect clinical utility. Prospective outcomes of > 50K pts treated based on 21-gene RS results have shown that pts with low RS EBC can safely forgo chemotherapy. Because of its extensive validation and wide clinical use, the RS assay is a common comparator in head-to-head studies with other assays.
Published/presented studies of the RS assay performed on same tumor samples with Breast Cancer Index (BCI), EndoPredict (EP) or EP+clinical features (EPclin), MammaPrint (MMP), and/or Prosigna (ROR) assays were reviewed. Study findings were summarized descriptively.
14 studies were found that compared the RS assay with BCI (1), BCI, EPclin, and ROR (1), EP/EPclin (2), MMP (6), and ROR (4). Overall discordance in risk stratification ranged from 43% to 66% between assays (Table). The RS assay classifies 12% of pts as high risk, compared with EP (63%), EPclin (48%), and MMP (46%), assays with low/high risk groups, and compared with BCI (16%) and ROR (33%), assays that, like the RS assay, use three risk groups.Table:
|Discordancea Between the RS Assay and Other Assays|
a. Overall=any discordance in risk classification between the RS assay and other; 1-level=discordance of one risk category (low ↔ intermediate or intermediate ↔ high); 2-level=discordance of two risk categories (low ↔ high). b. Four studies lacked risk classification information appropriate for inclusion in this table. c. Study used nonstandard RS cutoffs for the RS vs. MMP comparison.
The five most common genomic assays in clinical use for EBC risk-stratify pts differently and thus are not interchangeable. Of these, the RS assay classifies the smallest proportion of pts as high risk.
Clinical trial identification
Legal entity responsible for the study
Z. Varga: Consultant/advisor: Genomic Health, Roche. P. Sinn: Advisor: Genomic Health. D. McCullough, A. Lau, M.C. Stöppler, F.L. Baehner, C. Chao: Employment and stock ownership: Genomic Health. A. Seidman: Consultant/speaker: Genomic Health.