Mainz, May 15, 2017: BioNTech Diagnostics GmbH today announced the publication of an international prospective multicenter study that demonstrates the high reproducibility of the MammaTyper® in vitro diagnostic test. MammaTyper® determines the mRNA expression of the St. Gallen Guideline-recommended biomarkers HER2 (ERBB2), ER (ESR1), PR (PGR) and the proliferation marker Ki-67 (MKI67) by reverse transcription quantitative real-time PCR (RT-qPCR). In this study, ten renowned pathology laboratories – Prof. Varga (Zurich), Prof. Lebeau (Lübeck), Prof. Bu (Chengdu, China), Prof. Hartmann (Erlangen), Prof. Penault-Llorca (Clermont-Ferrand), Prof. Symmans (Houston, Texas), Prof. Teng (Hangzhou, China), Prof. von Wasielewski (Hannover), Prof. Bartlett (Ontario, Canada) and Prof. Viale (Milano) – analyzed the same clinical breast cancer tissue samples using the MammaTyper® test. The results were subsequently analyzed for their reproducibility both between the institutes (inter-site) and within each institute (intra-site). The data shows that MammaTyper® provides virtually identical results – independent of the location, the time of day, the instruments used and the operator performing the test . “The very precise reproducibility of MammaTyper® compared to immunohistochemistry was shown, especially for the determination of the proliferation marker Ki-67, which is vitally important for the differentiation of luminal breast cancer types and for the prognosis“, explained the head of the study, Prof. Dr. med. Zsuzsanna Varga, University Hospital of Zurich. “The study shows impressively that MammaTyper® has the potential to significantly increase not only the current standards but also the quality of breast cancer diagnostics“, affirms Dr. Sierk Pötting, CEO BioNTech Diagnostics GmbH.
The precise and reliable determination of the four biomarkers HER2 (ERBB2), ER (ESR1), PR (PGR) and Ki-67 (MKI67) is a key parameter that supports breast cancer therapy decisions. Ki-67 is of special interest in this respect, since in patients with luminal tumors, which are ER- and/or PR-positive and HER2-negative, the decision for or against chemotherapy is increasingly made on the basis of the Ki-67 value. The established immunohistochemistry (IHC) method has, however, been subject to review for some time – especially in terms of the reproducibility and comparability of Ki-67 results [2,3].
The recently published study examines whether the MammaTyper® in vitro diagnostic test is able to supply reliable and reproducible results for the mRNA expression of the genes ERBB2, ESR1, PGR and MKI67. . Ten internationally recognized pathology laboratories participated in the study, which was subdivided into two arms. In the first study arm, each institute analyzed RNA samples that had been centrally extracted from formalin-fixed paraffin-embedded (FFPE) breast cancer tissue samples. In the second arm, each institute was provided with FFPE tissue sections, from which RNA was locally extracted using the RNXtract® kit, to also take into account a possible variance through the preparation of the samples. On several days, each institute repeatedly examined each of these samples with the MammaTyper®. The reproducibility of the quantitative results for the individual markers both between and within the institutes was calculated by means of variance component analysis and the intra- and inter-class correlation coefficient (ICC). In the process, the ICC reflects the reproducibility of quantitative results over the entire measuring range . Furthermore, the agreement of positive/negative marker results and the subtype classification were interpreted on the basis of Fleiss‘Kappa values.
The first study arm examined the comparability of quantitative marker results (40-DD Cq values) between the ten sites. The total standard deviation of measurements of centrally extracted samples was merely 0.29 Cq for ERBB2, 0.44 Cq for ESR1, 0.18 Cq for PGR and 0.29 Cq for MKI67. Agreement of the four markers in locally extracted samples was similarly high. The mean deviations of individual markers over all samples at one site were close to zero, with values between -0.22 and 0.31 . Within the laboratories, ICC values of the quantitative determination of all markers ranged from 0.976 to 0.996, and across locations from 0.980 to 0.998, which demonstrates excellent precision of the quantitative determination.
Inter-site reproducibility of the positive/negative marker results was also correspondingly high – with Kappa values of 1.00, 0.91, 0.94 and 0.94 for ERBB2, ESR1, PGR and MKI67. The resulting subtype definition was virtually identical, with a Kappa value of 0.90 at the ten sites .
In contrast, IHC in comparable studies for Ki-67 only reaches an ICC value of 0.71 across the sites with local staining . Even with centralized staining, the IHC inter-site ICC values were similar – between 0.40 and 0.74, with Kappa values from 0.29 to 0.58 .
“The study proves the outstanding reproducibility of MammaTyper®. Thus, MammaTyper® has the potential to improve significantly the quality and reliability of breast cancer diagnostics“, Prof. Varga sums up.
The newly published data support the already published studies, which had substantiated the analytical precision of MammaTyper® and its high reproducibility compared to the established IHC method [6,7].