High frequency of microsatellite instability and its substantial co-existence with and mutations in Vietnamese patients with colorectal cancer.

Tumor heterogeneity and resistance to chemotherapy have been recognized as two major obstacles in the diagnosis and treatment of colorectal cancer (CRC). Microsatellite instability (MSI) and and mutations are common diagnostic factors that have been widely used to classify CRC for therapeutics. In the present study, 151 patients with CRC were analyzed from the two most populous ethnic groups of Vietnam, Kinh and Muong, for their MSI status, frequency of and mutations, and their clinical implications. MSI-high (MSI-H) was detected in 45.0% (68/151), while mutated and were identified in 37.1% (56/151) and 2.6% (4/151) of the cases, respectively. There was a substantial co-existence of MSI-H with (27/56; 48.2%) and (3/4; 75.0%) mutations. Statistical analysis showed that MSI-H tumors were significantly associated with colon location (P=0.011) and more advanced T stages (P=0.016). exon 2 mutations were significantly more likely to be detected in patients who belonged to the Muong ethnic group (P=0.013) or those with no/fewer lymph node metastasis (P=0.048) as compared with their counterparts. In summary, the data revealed typical molecular features of Vietnamese patients with CRC, including a strikingly high rate of MSI-H and its high co-existence with and mutations, which should be carefully considered in the future therapeutics for this type of cancer.