QuantiGene 2.0 Assay for ER, PR and HER2 RNA Levels Is a Useful Adjunctive for the Evaluation of ER, PR and HER2 in Breast Cancer.

Abstract

Abstract Immunohistochemistry (IHC) for the estrogen receptor (ER) and progesterone receptor (PR) is an established procedure in the routine treatment of patients with breast cancer, primarily to predict responses to hormonal therapy. HER2 IHC and FISH are also recommended to select patients for anti-HER2 based therapy. The IHC method for ER and PR is semi-quantitative and needs standardization. Furthermore, ER and PR RNA levels are continuous variables and quantitative measurement of ER levels can help predict the tamoxifen benefit breast cancer. In this study, the RNA levels of ER, PR and HER2 were measured using the QuantiGene 2.0 assay in formalin-fixed, paraffin- embedded (FFPE) tissue samples from breast cancer (n=40) and compared with conventional ER/PR IHC results and HER2 FISH results. There were no cases of discrepancy in ER status between staining with the SP1 antibody and staining with the 6F11 antibody; however, the ER score was statistically different between them (5.3 ± 3.3 vs. 4.9±3.2, P=0.02). One out of 40 cases (2.5%) showed a false negative result when performed using a 2mm representative tissue sample (TMA), and 1 out of 40 cases (2.5%) showed a discrepant ER status between the results using the Allred scoring system and the fractional scoring system. These results reconfirmed that various factors such as the primary antibodies used, interpretation methods and TMA vs. whole section, influence the results of IHC. When the cut-off values for ER, PR and HER2 RNA levels were 5.0, 7.2 and 50, respectively, the sensitivity, specificity, positive predictive value and negative predictive value of the QuantiGene 2.0 Assay were 96.6%, 90%, 96.7% and 90%, respectively, for ER; 89.7%, 81.8%, 92.9% and 75% for PR, and 83.3%, 96.4%, 90.9% and 93.1% for HER2. The Allred scores for ER and PR were correlated with RNA levels (P=0.046, R=0.32; P=0.00, R=0.61, respectively), and the HER2 FISH ratio was correlated with RNA levels (P=0.00, R=0.76). In conclusion, measuring ER, PR and HER2 RNA levels, which is known to have additional benefits in patient treatment, from FFPE tissue may be a helpful adjunctive in determining the status of ER, PR and HER2 in breast cancer. And the QuantiGene 2.0 assay, which does not require an RNA extraction step, uses FFPE samples, and expensive modern equipment, is easy to perform even in a small scale laboratory. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4153.