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Quantitative Single-Gene Scores

The Oncotype DX assay report now includes quantitative scores for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) gene expression by RT-PCR (all reports generated as of September 20, 2008). ER, PR and HER2 are three of the genes measured in the determination of the Recurrence Score result.

ER and PR

ER Brochure

• Continuous Measurement by RT-PCR:
  ER/PR status is critical in determining the use and estimating the benefit of adjuvant hormonal therapy. Breast cancers show a broad range of hormone receptor expression, and RT-PCR is able to accurately convey this continuum. RT-PCR is able to measure ER and PR as a continuous distribution of gene expression over a 3,000-fold and 1,000-fold range, for ER and PR, respectively.A quantitative ER Score can provide further insight into treatment decisions by helping to determine the magnitude of tamoxifen benefit for an individual patient (the higher the ER score, the greater the likelihood of tamoxifen benefit).
  * Data on file from Paik et al, NEJM, 12/30/2004.
  
• Concordance:
  The Oncotype DX assay determines ER and PR status (positive or negative) by measuring gene expression at the RNA level. There is a high concordance between ER and PR status as determined by the Oncotype DX assay and by immunohistochemistry (IHC), which measures ER and PR gene expression at the protein level.Studies were performed with ECOG (E2197 study, 769 patient samples) and Northern California Kaiser Permanente (607 patient samples):
• The Relationship Between ER/PR and the Recurrence Score Result:
  The Recurrence Score (RS) result can be either low or high for high ER levels. The RS result combines the ER level (related to response to tamoxifen) with the expression of other genes. The RS result is a better predictor of distant recurrence at 10 years given 5 years of tamoxifen therapy in the ER+ population than  ER/PR status is alone.

HER2

HER2 Brochure

HER2 is an important marker for therapeutic decision-making for patients with breast cancer, and its measurement significantly impacts the chosen course of treatment.

• Quantitative HER2 Information:
  A HER2 Score by the Oncotype DX assay is another measure for clinicians and patients to determine HER2 status, and it provides further insight into individual patients’ breast cancer tumor biology, although the Recurrence Score result remains the best tool for assessing prognosis and prediction of chemotherapy benefit.
• Highly Concordant with IHC¹² and FISH¹³:
  The Oncotype DX assay’s concordance with IHC and FISH meets or exceeds the ASCO/CAP guidelines requirement of 95% for determination of HER2 status.
• Added Clinical Information:
  Many clinicians who rely on the Oncotype DX assay for treatment planning have requested that Genomic Health also report a quantitative HER2 Score as this is already a component of the Recurrence Score result. – To provide further clarification especially in cases of equivocal IHC and/or FISH results or discordance between FISH and IHC.
• Addressing a Limitation with Current Testing:
  The impact of preanalytical variability can be minimized by “normalization” strategies used in quantitative gene expression assessment as performed by quantitative RT-PCR by the Oncotype DX assay.