in East Germany. A time trend analysis including 147,790 cases

Introduction: The incidence rate ratio of colon to rectal cancer is usually about 2:1. It has been observed for a while that the incidence of colon cancer among men (as opposed to women) in the Former German Democratic Republic (GDR) is lower than the rate of rectal cancer. Detailed analyses of this phenomenon have not been done so far. The aim was to give insights in this observation by de tailed incidence and mortality analyses and to explore the worldwide ratio of colon and rectal cancers based on population-based cancer registry data. Methods: We analyzed age-standardized incidence and mor tality data of colorectal cancers in East Germany (1961-1989 and 1996-2002; mortality 1980-2002), West Germany, Saarland (1970-2002) and all over the world (1978-82 up to 1993-97). Results: With the incidence increase of colorectal cancers in the GDR, the ratio of colon to rectal cancer incidence became larger and surpassed the reference value (ratio = 1) during the time of the reunification. Also the mor tality data revealed a similar pattern. Estimated an nual percentage increases of colon subsite incidences tended to be higher within the distal colon as com pared to the proximal colon Conclusions: Our anal yses of international cancer registries over a period of 20 years show that the colon-rectum cancer ratio is positively associated with the overall incidence of colorectal cancer with a stronger association among women than men. Non-causal factors such as un derdetection or registration artefacts are unlikely to explain the unusual colon/rectal rate ratio among men. A gradual decrease of the job-related physical activity among men may have contributed to the findings.