Observations on the epidemiology of gastrointestinal and liver cancers in the Asia-Pacific region.

Gastric cancer (GC) has long been thought to be an Asian type of cancer that is broadly associated with poverty, whereas colorectal cancer (CRC) has been thought to be a Western type of cancer associated with affluence. The incidence of GC has declined dramatically in the West but has a very high incidence in East Asia. The age-standardized incidence rates (ASR) have also declined. The decrease in the incidence of GC is associated with the decrease in the prevalence of Helicobacter pylori (H. pylori) infection worldwide. The discrepancy between a high H. pylori infection rate and a low GC incidence is seen chiefly among southern Asians of Indian origin and has been aptly termed the "Indian enigma". CRC is a new emerging cancer in this region. Some of the highest CRC ASR have been reported from Asian countries, in many of which it has now surpassed that of GC. Liver cancer is also an important cancer in the Asia-Pacific region. The highest ASR worldwide is reported from the Asian countries of Mongolia, Korea and Japan. The predominant underlying etiology across the region has been hepatitis B virus infection, except in Japan, where hepatitis C is an important cause of hepatocellular carcinoma (HCC). With mass vaccination of hepatitis B at birth and improved public health measures in many countries, hepatitis B and C are set to decline with time. However, the exponential increase in obesity and consequent non-alcoholic fatty liver disease portends a future epidemic of fatty liver-related HCC.