Microsatellite instability evaluation by a novel PCR‐based 8‐loci test kit in colorectal cancer

Abstract Microsatellite instability (MSI) assessment is strongly recommended for colorectal cancer patients, as MSI status is crucial in determining optimal treatment and predicting prognosis. This study evaluated the reliability and accuracy of a novel polymerase chain reaction (PCR)‐based 8‐loci MSI test kit, a rapid test kit designed to detect MSI, by comparing its performance with immunohistochemistry (IHC) and the National Cancer Institute (NCI) 2B3D Panel. MSI status was determined in 186 formalin‐fixed paraffin‐embedded (FFPE) colorectal cancer tissue samples with known mismatch repair (MMR) status by IHC using the novel PCR‐based 8‐loci MSI test kit. Additionally, the consistency between the NCI 2B3D Panel and the novel PCR‐based 8‐loci panel was compared using 69 FFPE tumor tissues paired with adjacent non‐cancerous tissue. The novel PCR‐based 8‐loci MSI test kit and IHC demonstrated high concordance (overall agreement: 97.8%). However, four samples displayed discordant results, exhibiting MMR deficiency using IHC and microsatellite stability using the novel PCR‐based 8‐loci MSI test kit. Of the 69 samples reanalyzed using the NCI 2B3D Panel, high concordance with the novel PCR‐based 8‐loci MSI test kit was observed in 67 of 69 cases (overall agreement: 97.1%). The novel PCR‐based 8‐loci MSI test kit is a rapid and reliable tool for accurately detecting MSI status in colorectal cancer.