Colorectal carcinoma among ethnic Chinese in Singapore - Trends in incidence rate by anatomic subsite from 1968 to 1192

BACKGROUND. Recent epidemiologic studies have suggested that the distributi on of colorectal carcinoma may have undergone a distal to proximal over sev eral decades, which has been attributed variously to environmental and gene tic factors as well as preventive intervention. METHODS. Trends in subsite distribution and the incidence rate of colorecta l carcinoma among Chinese in Singapore between 1968 and 1992 were explored using data from the Singapore Cancer Registry (n = 10,489). Age-standardize d incidence rates were computed and compared further using age-period-cohor t models by subsite and gender. RESULTS. The proportion of lesions in the distal colon was found to have in creased from 23.2% to 24.4% whereas that for the proximal colon and rectum were fairly consistent over the past 25 years. Our results also showed that age-standardized rates have doubled in proximal lesions (2-3% annually) an d more than doubled in distal lesions (3-4% annually) whereas rates in rect al carcinoma have shown a slight increase or stability over time. The patte rns of change in all subsite tumors could be attributed to a significant bi rth cohort effect. CONCLUSIONS. The results of the current study suggest that incidence rates have increased rapidly with no distal to proximal shift observed among ethn ic Chinese in Singapore over the past 25 years. The pattern of change diffe rs from findings reported in high incidence countries such as the U.S. and parts of Europe, suggesting that the preventive intervention and early diag nostic capabilities that may have played an important role in these countri es have had less effect in Asia. The rapid overall increase in the incidenc e rate of colon carcinoma supports the role of dietary and other environmen tal factors as possible risk factors. Cancer 1999;85:2519-25. (C) 1999 Amer ican Cancer Society.