Abstract 2939
Background
Detection of microsatellite instability (MSI) is recommended to identify colorectal cancer (CRC) patients with Lynch syndrome, but MSI is present in several other tumor types such as ovarian and gastric cancer. Current clinical reference methods to detect MSI stain for mismatch repair proteins or analyze frequently mutated DNA repeat regions. The Idylla™ MSI Test is being developed for a unique set of novel biomarkers (Zhao et al. 2014; eLife) capable of faster detection with greater specificity and selectivity compared to current methods.
Methods
To assess the suitability of the novel marker set to detect MSI status in gastric cancer, we performed a small-scale evaluation study: 10 novel MSI biomarkers with proven efficacy in CRC were tested in 150 gastric cancer samples. Repeat length was determined on FFPE DNA by PCR followed by melting curve analysis. Eighty-five samples were screened with a reference methodology for MSI detection (Promega MSI analysis system).
Results
Fifteen out of 150 samples (10%) were classified as MSI-H with the novel set of biomarkers. At least 5/10 (50%) of the markers scored mutant in each of these 15 samples. All of the 10 markers scored wild type in 131/150 samples. All samples with at least one mutant marker (n = 19) and 66 randomly selected samples with no mutant markers were screened with the Promega MSI analysis system. 9/85 samples failed with the reference method, even after repeat testing, while the Idylla™ methodology did not generate any failures (0/150). For 76 samples with results available for both methods, the overall percent agreement was 100% (76/76).
Conclusions
Fifteen out of 150 samples (10%) were classified as MSI-H with the novel set of biomarkers. At least 5/10 (50%) of the markers scored mutant in each of these 15 samples. All of the 10 markers scored wild type in 131/150 samples. All samples with at least one mutant marker (n = 19) and 66 randomly selected samples with no mutant markers were screened with the Promega MSI analysis system. 9/85 samples failed with the reference method, even after repeat testing, while the Idylla™ methodology did not generate any failures (0/150). For 76 samples with results available for both methods, the overall percent agreement was 100% (76/76).
Clinical trial identification
Legal entity responsible for the study
Biocartis NV, Mechelen, Belgium
Funding
EMD Serono Research & Development Institute, Inc.
Disclosure
B. De Craene: Employee with Biocartis. Z. Feng: Employee EMD Serono, a business of Merck KGaA, Darmstadt, Germany. Eligible for the Merck KGaA Long-Term Incentive Award. Stock owner of Argos Therapeutics Inc. (ARGS). Member of American society of clinical pathologists (ASCP). E. Rondelez: Employee with Biocartis. L. Vandenbroeck: Employee with Biocartis. K. Peeters: Employee with Biocartis. G. Maertens: Employee with Biocartis. E. Sablon: Employee with Biocartis. T. Cai: Employee with EMD Serono, a business unit of Merck KGaA, Darmstadt, Germany.