Trends in colorectal cancer incidence in Ho Chi Minh City, Vietnam (1996–2015): Joinpoint regression and age–period–cohort analyses

1

Introduction

Globally, colorectal cancer (CRC) is the third most frequently diagnosed cancer and the second most common oncological cause of death in both genders, with 1931 million new cases and 935,173 deaths in 2020 [1] . In Vietnam, CRC was one of the five leading cancers between 2000 and 2018 [2] . Importantly, CRC treatment results in a considerable economic burden; the estimated total cost in Vietnam was up to $132.9 million, representing 0.055% of the 2018 gross domestic product [3] .

Asian populations historically have had a lower risk for CRC than people in Western countries [4] . However, for the past decades, CRC incidence has increased in Asia, from low-income to high-income countries. From 2015 to 2018, the age-standardized incidence rate (ASR) of CRC increased from 18.3 to 19.9 per 100,000 of the population in Malaysia, 12.4 to 15.5 per 100,000 of the population in Thailand, and 13.1 to 18.9 per 100,000 of the population in the Philippines [5] . The rising rate was steeper by two- to four-fold among high-income Asian nations, including Japan, South Korea, China, Singapore, Hong Kong, and Taiwan [67] . Notably, South Korea was ranked as having the second highest ASR of CRC worldwide at 44.5 per 100,000 of the population [8] . The most likely explanation for these increasing rates in Asia is the rising prevalence of a westernized lifestyle, such as unhealthy diet, obesity, physical inactivity, and smoking [910] .

CRC has been deemed a disease burden only among older individuals, as CRC development rates elevate significantly after the age of 50 [11] . Nevertheless, several recent studies indicated a notably increasing incidence of early-onset CRC in Western countries 1213141516 . Early-onset CRC may have a family history or genetic predisposition; however, most cases observed (approximately 75%) are sporadic [10] . Because of the rising prevalence of early-onset CRC, the initiative of screening before the age of 50 is relevant [12] . With the trend of CRC in many Asian nations being in line with those in Western populations, it could be expected that a similar rise in early-onset CRC in Asia is on the way.

Studies in Asian populations have shown that the anatomical subsite distribution of CRC was different. An increasing proportion of proximal colon cancer has occurred in Japan, China, and Israel, while rates of distal colon and rectal cancer have taken the lead in Korea 17181920 . Knowing the dominant CRC subsite may be helpful in choosing either flexible sigmoidoscopy or total colonoscopy in primary screening for CRC in a population-based program [21] .

In Vietnam—a middle-income Asian country—we lack comprehensive analysis of the trends in CRC incidence by age, sex, and tumor subsite on either a regional or a national scale. It is still unclear whether CRC in Vietnam is on the rise in parallel with that in other Asian countries, and whether the younger-onset incidence trend is occurring. Therefore, we aimed to investigate the trends in epidemiology and anatomical subsites of CRC in Ho Chi Minh City, Vietnam, from 1996 to 2015. Additionally, we performed an age–period–cohort (APC) analysis to estimate the contributions of age, period, and cohort effects on the observed trend. To our knowledge, this is the first study to examine the effect of age and birth cohort on CRC incidence in Vietnam.