We searched PubMed and MEDLINE from 1985 to 2005 with the keywords “colorectal cancer”, “incidence or mortality”, “screening”, and “Asia or Asian”. Only full papers and abstracts published in English were included. Cancer statistics were retrieved from the World Health Statistics of the WHO Databank, Cancer Incidence in Five Continents (volumes I to VIII), and GLOBOCAN 2002 of the International Agency for Research on Cancer. We searched the national cancer registries of individual Asian
ReviewIncreasing incidence of colorectal cancer in Asia: implications for screening
Introduction
Colorectal cancer (figure 1) has traditionally been one of the commonest malignant disorders in western populations, whereas cancers of the upper gastrointestinal tract (oesophagus and stomach) and liver have predominated in the east. However, during the past few decades, there have been remarkable changes in the incidence of colorectal cancer in Asian countries. In 2004, the Asia Pacific Working Group on Colorectal Cancer was formed, with representatives from ten Asian countries (China, India, Indonesia, Japan, South Korea, Malaysia, the Philippines, Singapore, Taiwan, and Thailand) to address this issue. Members are non-governmental key opinion-leaders representing their individual countries in the Asia Pacific Society of Digestive Endoscopy, which is affiliated to the Organisation Mondiale D'Endoscopie Digestive. We review here the changing epidemiology of colorectal neoplasms in the Asia Pacific countries with a special emphasis on the effect of screening for colorectal cancer in this region.
Section snippets
Changes in epidemiology of colorectal cancer
Some of the more developed and westernised Asian countries have already experienced a rapidly rising trend in colorectal cancer. Data from the CancerBase of the International Agency for Research on Cancer (IARC) show that the incidence in many affluent Asian countries is similar to that in the west (figure 2). The age-standardised rate of colorectal cancer per 100 000 men is 49·3 in Japan, 24·7 in South Korea, and 35·1 in Singapore, compared with 44·4 in North America and 42·9 in western Europe.
Ethnicity, migration, and lifestyle
There are many different ethnic groups in Asia with substantial differences in incidence of colorectal cancer. In Singapore, where three major ethnic groups live in the same environment, the incidence of colorectal cancer is significantly lower among the Indian and Malay populations than among the Chinese population.13 The lower rates in Malays and Indians are evident also when age-adjusted data are compared.14 A similar pattern has been observed in Malaysia, where Chinese people have a
Distribution of colorectal cancer in Asian patients
In a retrospective cohort study comparing 690 patients with colorectal cancer presenting consecutively to the Cleveland Clinic, OH, USA, and 870 patients in Guangzhou, China, between 1990 and 2000, a difference in anatomical distribution of colorectal cancer was found.23 Proximal cancers (in this study the proximal colon included the caecum, ascending colon, hepatic flexure, transverse colon, and splenic flexure) were more common in the US than in the Chinese cohort. Data from the Japanese
Non-polypoid tumours and de-novo colorectal cancer
Although most cases of colorectal cancer are thought to arise from a sequence of adenoma to carcinoma, evidence from Asia (Japan particularly) suggests another mechanism. Clinicopathological studies have shown that there are two groups of colorectal cancers—polypoid and non-polypoid (superficial) tumours. The latter are flat lesions with a raised or depressed surface.29 By use of the same techniques as in screening for gastric cancer, Japanese endoscopists found colorectal cancers smaller than
Are we ready for screening for colorectal cancer in Asia?
Although colorectal cancer has emerged as an important neoplastic disease in Asia, much remains to be studied before a population-based screening programme can be set up. The epidemiology (eg, characterisation of high-risk populations, differences between ethnic groups, distribution of colorectal neoplasms) has not been thoroughly studied in many Asian countries. National registries of colorectal cancer representing the whole country are available only in Singapore, Hong Kong, and, recently,
Search strategy and selection criteria
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