Study of Concordance between RT-PCR and Immunohistochemical Testing of Hormone Receptor and HER2 Status in Breast Cancer Specimens.
Rutika Mehta, Rohit K Jain, Payal M Sojitra, Yesim Gokmen-Polar, Sunil Badve. Indiana University School of Medicine, Indianapolis
Background: The need for good prognostic and predictive markers is vital to breast cancer management. The 21- gene RT-PCR assay (Oncotype Dx) has enabled the estimation of recurrence risk in estrogen receptor (ER) positive patients. With widespread use of this assay in routine clinical practice, the question remains if receptor status detection is perfect by any of immunohistochemistry (IHC) or RT-PCR. This study is a retrospective analysis of all Oncotype Dx reports and their corresponding pathology reports at our institution to determine the concordance of the receptor status between IHC and RT-PCR and correlate them with important clinico-pathological variables.
Design: Our institution houses over 300 reports of Oncotype Dx assay performed on pathological tumor blocks from patients operated or treated here. These patients were seen at this instutuion between 2004 and 2010 and were referred for the Oncotype Dx assay after being verified as ER and/or PR positive. The HER2 RT-PCR scores were categorized as negative (<10.7) or positive (≥11.5) using assay guidelines. Any case with positive result on IHC and/or FISH for HER2 was considered as positive for this receptor.
Results: For 228 patients, the individual RT-PCR scores for ER and PR as well as their immunohistochemical percentage staining were available. HER2 information by qRT-PCR as well as by IHC/FISH was available for 164 patients only. Unequivocal cases by IHC/FISH or RT-PCR HER2 were excluded for the purpose of clarity. A strong correlation between ER status by IHC and RT-PCR score from the Oncotype DX assay reports (r=0.30, 95% CI: 0.174-0.419; p<0.0001) was noted. Similar observations were noted for concordance of PR IHC percentage staining with RT-PCR scores (r=0.62; 95% CI: 0.532-0.698; p<0.0001). A strong concordance of HER2 results (98%) was observed when RT-PCR results were compared with IHC/FISH data (p=0.002).There was one equivocal case by RT-PCR which was also equivocal by IHC as well as FISH.
Conclusions: A very strong concordance is noted between IHC tests used to detect receptor status during routine pathological practice and centralized quantitative RT-PCR results obtained by the Oncotype-Dx assay. The single gene expression data can be safely to used to assess quality/ performance of IHC in clincal laboratories.
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 9, Wednesday Morning