What is the role of molecular profiling assays in the workup of breast cancer?

Updated: Feb 04, 2021
  • Author: Pavani Chalasani, MD, MPH; Chief Editor: John V Kiluk, MD, FACS  more...
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The Onco type Dx assay (Genomic Health, Inc, Redwood City, CA) has been approved by the US Food and Drug Administration (FDA) for women with early-stage ER-positive, node-negative breast cancer treated with tamoxifen, where the recurrence score (RS) correlated with both relapse-free interval and overall survival. This assay is an RT-PCR–based assay of 21 genes (16 cancer genes and 5 reference genes) performed on paraffin-embedded breast tumor tissue.

By using a formula based on the expression of these genes, an RS can be calculated that correlates with the likelihood of distant recurrence at 10 years. Breast tumor RSs and risk levels are as follows:

  • < 18, low risk

  • 18-30, intermediate risk

  • >30, high risk

Furthermore, in the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14 and B-20 studies, the Onco type Dx assay was shown retrospectively to predict benefit from chemotherapy and hormonal therapy in hormone-sensitive, node-negative tumors. [110] Similarly, among women with 1- to 3-node-positive, hormone receptor-positive disease, the Onco type Dx recurrence score was a significant predictor of recurrence, with a 21% decrease in recurrence risk for each 10-point drop in RS.

Women with a low RS showed a significantly greater improvement in disease-free survival (DFS) with the addition of tamoxifen; no additional benefit was derived from the addition of chemotherapy. In contrast, women with a high RS had a significant improvement in DFS with the addition of chemotherapy to hormonal therapy (tamoxifen).

The benefit of adding chemotherapy to hormonal therapy in tumors with an intermediate score is still controversial. The Trial Assigning Individualized Options for Treatment [TAILORx], a large, prospective, randomized phase III study sponsored by the National Cancer Institute (NCI), is addressing this important question.

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