Abstract 5205: Changes in trends in colorectal cancer incidence rate by anatomic site between 1978 and 2004 in Japan

Abstract

Abstract Although colorectal cancer (CRC), a major cancer worldwide, has shown a proximal or right-sided shift in subsite distribution in western countries, trends in subsite incidence in Asian countries remain unclear. Here, we evaluated subsite-specific trends in CRC incidence rate between 1978 and 2004 in Japan using large data from 10 population-based cancer registries. The colorectal sites (C18-20) were categorized into three groups, proximal colon (C18.0-18.5), distal colon (C18.6-C18.7) and rectum (C19.9 and C20.9). Trends in age-standardized incidence rates (ASRs) were characterized by Joinpoint regression analysis. A total of 474,651 colorectal cancer cases were analyzed. Overall, ASRs increased remarkably until 1993, with an annual percent change (APC) of 4.9%, and then stabilized thereafter. By subsite, however, ASRs of proximal colon significantly increased, with APCs of 7.1% (1978∼1991), 3.8% (1991∼96) and 0.9% (1996∼2004); distal colon showed an initial significant increase, with an APC of 7.6%, but stabilized from 1991 until the end of observation; and rectal cancer showed an initial significant increase, with APCs of 1.9% (1978∼88) and 5.6% (1988∼92), but then decreased abruptly in 1992, the year colorectal cancer screening was introduced nationwide, with an APC of -1.0%. Thus, we revealed that changes in incidence trends for the three anatomic sites apparently began to differ in the 1990s, and this is a first report to our knowledge. We also discuss factors that could explain these changes in Japanese. Careful monitoring is necessary to confirm whether these trends are changing in the Japanese population. Citation Format: Hiroko Nakagawa, Hidemi Ito, Satoyo Hosono, Isao Oze, Haruo Mikami, Masakazu Hattori, Yoshikazu Nishino, Hiromi Sugiyama, Kayo Nakata, Hideo Tanaka. Changes in trends in colorectal cancer incidence rate by anatomic site between 1978 and 2004 in Japan. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5205.