TY - JOUR T1 - 989 Analysis of microsatellite instability in endometrial cancers: comparative evaluation of molecular-based assays in formalin-fixed tissues JF - International Journal of Gynecologic Cancer JO - Int J Gynecol Cancer SP - A133 LP - A133 DO - 10.1136/ijgc-2021-ESGO.219 VL - 31 IS - Suppl 3 AU - P Gilson AU - J Levy AU - M Rouyer AU - J Demange AU - M Husson AU - C Bonnet AU - J Salleron AU - A Leroux AU - JL Merlin AU - A Harlé Y1 - 2021/10/01 UR - http://ijgc.bmj.com/content/31/Suppl_3/A133.2.abstract N2 - 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. ER -