Page 54 - 22-0424

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

specific genetic abnormalities in cancer. Several gene alterations are also inherited
in the family. Germline mutations in cancer susceptibility genes are associated with
very high risk of cancers in various organs. Identification of at-risk asymptomatic

individuals who do carry pathogenic mutations would allow early screening and
prevention of many cancers.

Similar to other chronic health conditions, several factors such as diet,
environment and lifestyle contribute to clinical variation of cancer. Some cancer
types are significantly more prevalent in Asian than in Western population (Ferlay
et al. 2019). Same cancers display difference in subtypes among countries. Similar
cancers from various ethnic groups also have different treatment outcome and
prognosis (Banegas and Li 2012). Genetic diversity also undeniably plays role
in phenotypic differences among various ethnic groups with the same cancer.
Knowledge on genome variation in different ethnicity would create better
understanding on underlying mechanisms of diseases, diagnostic strategies and
treatment selection. This article presents current information and examples on
ethnic diversity and cancer genomics that would have significant implication on
cancer precision medicine.

Non-Small Cell Lung Cancer

Lung cancer is one of the leading cancer types and causes of death worldwide.
It is the most common cancer in male and mainly associated with tobacco smoking.
Majority of lung cancer patients are diagnosed at advanced stage. Treatment
regimens for lung cancer are mostly palliative as many chemotherapeutic
regimens performed poorly (Schiller et al. 2002). Until 10 years ago, it was found
that a subset of lung cancer patients who were found to be East Asian, non-smoker
or light smoker, and had adenocarcinoma subtype of lung cancer, had a significant

survival benefit with Gefitinib treatment (Mok et al. 2009). Gefitinib is first selective
inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase domain. This
data had led to subsequent study and found that majority of those lung cancer
patients indeed harbored mutations in EGFR (Fukuoka et al. 2011). Studies on
lung cancer genome landscape showed racial disparity on cancer gene alteration
pattern. Data from The Cancer Genome Atlas (TCGA), consisting mainly Caucasian
population, demonstrated that TP53 is the most commonly mutated gene in lung
cancer, while EFGR mutations were observed in only 14% of cases (Cancer Genome
Atlas Research Network 2014). However, various study groups identified much

48 Cancer Precision Medicine and Ethnic Diversity

11/7/2565 BE 13:27
_22-0424(047-054)6.indd 48 11/7/2565 BE 13:27
_22-0424(047-054)6.indd 48