Summary of head‐to‐head comparisons of patient risk classifications by the 21‐gene Recurrence Score® (RS) assay and other genomic assays for early breast cancer

Many genomic assays that assess recurrence risk in early breast cancer (EBC) are prognostic, but they differ in risk group stratification, which can affect clinical utility. Prospective outcomes of >60K patients treated based on the 21‐gene assay results have shown that chemotherapy may be safely omitted in EBC patents with low Recurrence Score (RS) results (RS<18). 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 the 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 42% to 66% between assays. The RS assay classifies 12% of patients as high risk, compared with EP (63%), EPclin (48%), and MMP (46%) assays with dichotomous low/high risk groups, and compared with BCI (16%) and ROR (33%), assays that, like the RS assay, use three risk groups. The five most common genomic assays in clinical use for EBC risk stratify patients differently and thus are not interchangeable. Of these, the RS assay classifies the smallest proportion of patients as high risk and would therefore be expected to result in the fewest patients receiving chemotherapy.

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