| [ Summary ] |
Colorectal cancer (CRC) is the third most prevalent cause of cancer related mortality in Japan, and its incidence is gradually increasing. Age is a major risk factor for sporadic CRC. The lifetime incidence of CRC in patients at average risk is about 5 percent, with 90 percent of cases occurring after age 50. Recently, some authors have reported that the incidence rates for cancer in the right-sided colon have increased. We retrospectively analyzed the chronologically based trends related to surgical operation cases of CRC at the National Cancer Center Hospital, Tokyo between 1962 and 2009. There was a total of 8,296 (male : 4,913, female : 3,383, mean age: 60.9 years) CRCs in this period. All cases were divided into five groups based on the operation date as follows ; 1962-69 : 331 cases (M : 211, F : 120), 1970-79 : 629 (M : 338, F : 291), 1980-89 : 1,366 (M : 800, F : 566), 1990-99 : 2,188 (M : 1,333, F : 855), 2000-09 : 3,782 (M : 2,231, F : 1,551). In the first period (1962-69), approximately 60 % of CRCs were located in the recto-sigmoid colon (38 % were in the lower rectum). However, the incidence rate for rectal cancer decreased in contrast to right-sided colon involvement which gradually increased to approximately 30 % especially in females and elderly patients. Finally, we made a comparison of clinicopathological features contrasting lower rectal (Rb) lesions to other lesions. There were some differences in regard to the patient's age, gender and depth of cancer invasion. From our results, we concluded that it is crucial to perform total colonoscopies not only on younger patients but also elderly people and have an accurate knowledge of the current distribution of CRCs. |