Improvement of survival over time for colon cancer patients by anatomical sub-sites

The aims of this study are to describe and to evaluate improvement of survival over time for colon cancer patients by anatomical sub-sites. Data on 661 patients newly diagnosed as having colon cancer at Osaka Medical Center for Cancer and Cardiovascular Diseases from 1978 to 1991 were examined in this study. Corrected survival was calculated with the Kaplan-Meier method according to the period of diagnosis: early period (1978-84) and later period (1985-91). Factors concerning the difference in survival between the two periods were examined with the Cox proportional hazards regression model according to sub-site. Five-year corrected survival of the patients with left colon cancer improved significantly (60 to 72%; P < 0.01), probably due to advances in treatment, while that of patients with transverse colon cancer also improved significantly (39 to 67%; P < 0.01), mainly because of progress in diagnosis. The five-year corrected survival of those with right colon cancer did not increase (57 to 46%; P = 0.14), owing to lack of improvement in stage at diagnosis. Among the three sub-sites, the right showed the worst five-year survival in the later period. We concluded that survival of patients with right colon cancer, differing from the other anatomical sub-sites, did not improve, possibly because of lack of symptoms. The screening programs for colon cancer introduced in Japan in 1992 may be expected to improve the survival of patients with colon cancer, including that of the right colon.