THE ROLE OF MICROSATELLITE INSTABILITY IN COLORECTAL CANCER:
 LITERATURE REVIEW

Abstract

Relevance: According to Globocan 2020, colorectal cancer (CRC) incidence in Kazakhstan is lower than in all OECD countries except
 Mexico. However, the CRC incidence in Kazakhstan is steadily growing. In the structure of cancer incidence, CRC went up from 5th place in 2006
 to 3rd place in 2021. More than 80% of tumors associated with Lynch syndrome were found to have microsatellite instability (MSI). Thus, MSI is
 detected in 12% of sporadic colon tumors. At that, MSI in the tumor is caused by a decreased activity of DNA repair genes that can be due to both
 hereditary and somatic causes.
 The study aimed to systematize the current literature data to consider the need and adequacy of pre-scribing preventive chemotherapy, personalizing the treatment of patients, and predicting the course of the disease in CRC.
 Methods: A review was made of the published results of scientific and clinical studies for 2006-2021 from the PubMed, MedLine, and Cancer
 Observe database for the keywords “colon cancer,” “microsatellite resistance,” “adjuvant chemotherapy,” “PCR study,” “IGH-study.”
 Results: The value and adequacy of determining the IHC characteristics of the MSI status. The prognostic and predictive value of MSI in CRC
 has been proven. The optimal treatment options were determined depending on the status of MSI.
 Conclusion: Tumors with certain MSI status should be classified as a separate group of malignancies. Instability status determination is
 preferred in case of suspected Lynch syndrome, in patients with stage II CRC, as well as in clinical and histological features characteristic of MSI
 (proximal localization of the primary tumor, mucinous histotype, poorly differentiated tumors, lymphocytic infiltration of the tumor). Further determination of these tumors’ molecular characteristics will help stratify patients who may respond differently to chemotherapy. Also, the MSI status
 determination can be an importnant prognostic marker in patients whose tumors have a somatic mutation in the BRAF gene