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The International Journal of the Royal Society of Thailand
Volume XI - 2019

higher EGFR mutation rates among Asian patients. The study of more than 3,000
Chinese lung cancer patients found that 56% carried EGFR mutations regardless
of smoking status (Meng et al. 2019). Since the introduction of Gefitinib and other

EGFR inhibitors to standard treatment regimen for EGFR-mutated lung cancer,
clinical outcome of those NSCLC patients improved dramatically with overall
survival gain by average of 2 years with monotherapy. The survival effect is
found to be more beneficial among Asian patients than Caucasian counterparts.
Currently EGFR mutation testing becomes a routine diagnostic test for every
NSCLC case in Thailand and other countries, owing to a high prevalence among
Asian patients.

Colorectal Cancer

Colorectal cancer is more commonly found among Western than Asian
population. However, the prevalence of this condition among Asian countries is
on the rise for several reasons. Life expectancy of world population is increasing
with several countries across the globe entering aging population. Behavioral
and environmental factors between countries become convergent as we see Asian
population is increasingly westernized on dietary consumption and lifestyle.
Colorectal cancer is a heterogeneous disease with various histopathology, sites
of involvement, clinical behavior, response to treatment and prognosis. Previous
studies on gene expression patterns among colorectal cancers revealed many
distinct gene expression profiles that correlated with clinical phenotypes and
disease prognosis. These data were later unified into four consensus molecular

subtypes (CMS) with characteristic features. CMS1 demonstrates microsatellite
instability and strong immune activation. CMS2 has epithelial markers with marked
WNT and MYC signaling activation. CMS3 showed evidence of metabolic
dysregulation with KRAS mutations, and CMS4 has mesenchymal phenotypes
such as prominent transforming growth factor–β activation, stromal invasion and
signals for epithelial-mesenchymal transition (Guinney et al. 2015). A subsequent
study on molecular subtyping in Singapore and South Korea patients found that
11% of colorectal cancers was unable to assign to any CMS group (Ragulan et al.
2019). Another study of CMS classification on colorectal cancers from 4 different
countries (Thailand, Brazil, Mexico and USA) showed that colorectal cancer
subtypes differ by geographic region (Korphaisarn et al. 2020). A study on 5 most
commonly mutated genes in Thai colorectal cancers also showed more frequent
KRAS codon 146 and FBXW7 mutations than Western colorectal cancers

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