Increasing incidence of colorectal cancer in Asia: implications for screening.

Many Asian countries, including China, Japan, South Korea, and Singapore, have experienced an increase of two to four times in the incidence of colorectal cancer during the past few decades. The rising trend in incidence and mortality from colorectal cancer is more striking in affluent than in poorer societies and differs substantially among ethnic groups. Although changes in dietary habits and lifestyle are believed to be the reasons underlying the increase, the interaction between these factors and genetic characteristics of the Asian populations might also have a pivotal role. Non-polypoidal (flat or depressed) lesions and colorectal neoplasms arising without preceding adenoma (de novo cancers) seem to be more common in Asian than in other populations. The absence of polypoid growth preceding malignancy has posed difficulties in screening for early colorectal cancer by radiological imaging or even endoscopic techniques. Although epidemiological data are scanty, most Asian populations are not aware of the growing problem of colorectal cancer. More work is needed to elucidate the magnitude of the problem in Asia.