Abstract 2056
Background
The current analysis for the determination of Microsatellite Instability (MSI) status in tumors requires matched normal DNA as references. Five quasi-monomorphic markers (NR-21, BAT-26, BAT-25, NR-24, and MONO-27) of the Promega panel are known to have few variant alleles in both Caucasian and Asian patients (pts). For that reason, the peak of PCR products from normal DNA are confined within the Quasi-Monomorphic Variation Range (QMVR), of which Japanese pts with metastatic colorectal cancer (mCRC) are almost the same as those of Caucasian (Patil DT, et al., 2012 and Bando H. ASCO-GI 2017).
Methods
The purposes of this clinical evaluation study are to establish the QMVR in Japanese pts with mCRC and to evaluate the clinical utility of the QMVR in the determination of MSI status without matched normal DNA. The primary endpoint is the concordance of MSI status between the standard method using DNA from tumor plus matched normal samples and testing method using DNA from only tumor samples. The new MSI kits including the Promega MSI panel were manufactured under the Quality Management System (QMS) for in vitro diagnostics (IVDs). As the decision algorithm, tumors exhibiting 2 or more markers outside the QMVR were classified as MSI-H, cases with 1 marker or without any marker outside the QMVR were classified as non MSI-H (MSI-L/MSS).
Results
Totally 435 pts with mCRC were enrolled. Median age was 66 years old and 248 (57.0%) pts were male. 368 (84.6%) primary and 67 (15.4%) metastatic specimens were used. There were 11 (2.5%) MSI-H cases by the standard method and the sensitivity of the testing method was 100% while the specificity of the testing method was also 100%. Thereby the two methods was completely concordant. Among the five quasi-monomorphic markers, 3 and 2 cases were discordant in NR-21 and BAT-25, respectively. In BAT-26, NR-24, and MONO-27, all cases were completely concordant.
Conclusions
By using the QMVR, MSI status of Japanese pts with mCRC can be determined without matched normal DNA, and the QMVR might be applicable to Caucasian pts.
Clinical trial identification
UMIN000024144 Release date: March 26, 2016
Legal entity responsible for the study
FALCO Biosystems Co, Ltd.
Funding
FALCO Biosystems Co, Ltd.
Disclosure
W. Okamoto: Research funding from MSD. T. Fukui: Employment with FALCO Biosystems Co, Ltd. T. Yoshino: Research funding from GlaxoSmithKline K.K. and Boehringer-Ingelheim GmbH. All other authors have declared no conflicts of interest.