%0 Journal Article %A P Gilson %A J Levy %A M Rouyer %A J Demange %A M Husson %A C Bonnet %A J Salleron %A A Leroux %A JL Merlin %A A Harlé %T 989 Analysis of microsatellite instability in endometrial cancers: comparative evaluation of molecular-based assays in formalin-fixed tissues %D 2021 %R 10.1136/ijgc-2021-ESGO.219 %J International Journal of Gynecologic Cancer %P A133-A133 %V 31 %N Suppl 3 %X Introduction/Background*Microsatellite instability (MSI) is routinely analyzed in patients with endometrial cancers for selecting patients for immunotherapy. Standard reference methods recommended for MSI/dMMR (deficient MisMatch Repair) are immunohistochemistry and pentaplex PCR assays.Methodology We evaluated here the performance of a custom capture-based NGS method, digital droplet (dd)-PCR and automated-PCR for the determination of MSI status in 30 formalin-fixed paraffin embedded (FFPE) tissue samples from patients with endometrial and colorectal cancers. All samples have been previously characterized using standard reference methods, set as gold standard.Result(s)*Overall agreement, sensitivity and specificity were 93.3%, 93.8% and 92.9% for NGS. Overall agreement, sensitivity and specificity were 100% for dd-PCR and automated-PCR assays.Conclusion*NGS, dd-PCR and automated-PCR can be used routinely used for the analysis of MSI detection and represent complementary options to IHC and pentaplex PCR assays. Dd-PCR and automated-PCR assays allow easy and fast analysis while NGS allows simultaneous analysis of MSI and clinically relevant genomic alterations. %U https://ijgc.bmj.com/content/ijgc/31/Suppl_3/A133.2.full.pdf