PCR Better at Identifying Breast Tumor Subtypes than Immunohistochemistry

A recently published study suggested that a RT-qPCR (reverse transcription quantitative real-time polymerase chain reaction) assay was superior to classical immunohistochemistry for subtyping breast tumors.

The biological subtype of breast cancer influences the selection of systemic therapy. Distinction between luminal A and B cancers depends on consistent assessment of the marker protein Ki-67 (encoded by the MKI67 gene), but substantial intra-observer and inter-observer variability exists when immunohistochemistry (IHC) is used.

A study compared the BioNTech Diagnostics GmbH (Mainz, Germany) MammaTyper RT-qPCR-based diagnostic kit with IHC in the assessment of Ki-67 and other standard factors used in breast cancer subtyping.

MammaTyper is based on quantitative one step RT-qPCR technology, combining reverse transcription of mRNA and subsequent quantitative PCR of the resulting cDNA. Signal detection is performed in real time by fluorescently labeled hydrolysis probes. Expression results are normalized against two reference genes. Additionally a calibrator corrects for inter-run and inter-instrument variations. Besides quantitative and highly reproducible performance data the test kit delivers fast and reliable results by ready-to-use assay mixes.

Results of MKI67 mRNA expression measurements with MammaTyper showed that patients who expressed a low level of MKI67 had a significantly better prognosis with regard to disease-free survival and overall survival than patients with a high MKI67 expression. In contrast, measurement of Ki-67 protein expression by IHC showed no significant difference between these two groups for the prognosis of the two parameters.

The MammaTyper kit is CE / IVD marked for use in breast cancer subtyping. In addition to detection of MKI67, MammaTyper demonstrated precise quantitative detection of the biomarkers ERBB2 (HER2 - Human epidermal growth factor receptor 2), ESR1 (ER - Estrogen receptor alpha), and PGR (PR - Progesterone receptor).

"The positive study data for MammaTyper underline our commitment to making personalized medicine broadly available for treating cancer," said Dr. Sierk Poetting, managing director of BioNTech Diagnostics.

The study was published in the May 24, 2016, online edition of the journal Breast Cancer Research and Treatment.

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