THE ROLE OF MICROSATELLITE INSTABILITY IN COLORECTAL CANCER: A 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., MSI in cancer is caused by a decreased activity of DNA repair genes due
 to hereditary and somatic causes.
 The study aimed to systematize the current literature data to consider the need and adequacy of prescribing 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 databases 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 selected 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 important prognostic marker in patients whose tumors have
 a somatic mutation in the BRAF gene.