Prevalence estimation of microsatellite instability in colorectal cancers using tissue microarray based methods - A...

Area of Science:

• Oncology
• Gastroenterology
• Genetics

Background:

• Microsatellite instability (MSI) is a key factor in 15% of colorectal cancers (CRCs), including Lynch syndrome.
• MSI status significantly impacts CRC prognosis and treatment strategies.
• The prevalence of MSI in Indian CRC patients remains largely uncharacterized.

Purpose of the Study:

• To determine the prevalence of MSI in a cohort of Indian CRC patients.
• To correlate MSI status with clinical and histopathological features.
• To compare MSI prevalence in India with existing Western literature.

Main Methods:

• Immunohistochemistry (IHC) for four mismatch repair (MMR) markers (MLH1, MSH2, MSH6, PMS2) on 231 CRC cases.
• Tissue microarrays and whole tissue sections were utilized.
• Molecular MSI testing was performed on a subset of cases, with correlation to clinical data.

Main Results:

• A prevalence of 22.94% for MSI-H phenotype was observed in Indian CRC patients.
• MLH1-PMS2 and MSH2-MSH6 dual loss were the most common MMR deficiencies.
• Independent predictors for MSI-H included younger age (<60), right-sided tumors, and severe intratumoral lymphocytic response.

Conclusions:

• The prevalence of MSI-H CRC in India appears higher than reported in Western populations.
• Widespread MSI testing is crucial for improved clinical management of CRC.
• Enhanced testing facilitates the identification of potential hereditary colon cancer syndromes like Lynch syndrome.