Abstract
Background and Aims: More than 25 years ago, we established a colorectal cancer screening program which implements screening colonoscopy (SCS). However, the immunochemical fecal occult blood test (IFOBT) has been the only official screening method in Japan. The purpose of this study is to clarify the detection rates of colorectal cancer (CRC) by SCS and reveal the advantage of this method over that of IFOBT.
Methods: During the period between 1983 and 2008, 34,371 asymptomatic, average-risk individuals (male, 24,579; female, 9,792; mean age at the initial screening, 48.7 years) were enrolled in our colorectal cancer screening program. SCS was performed with skinny-caliber scopes (Olympus PCF), and sedation was applied only when indicated. In total, 125,006 screening colonoscopies were performed during this period. On the other hand, a one-time IFOBT was conducted simultaneously in these subjects during this period. The sensitivity of the IFOBT for colorectal cancer was investigated based on the SCS findings.
Results: Complete colonoscopy to the cecum was successful in 123,529 (98.9%) cases. CRC was detected in 314 (0.25%) of all the cases examined in all examinations; regarding the invasion depth, 195 cases (0.16%) were limited to within the mucosa, 47 (0.04%) were invasive to the sub-mucosal layer, and 72 (0.06%) were invasive beyond the sub-mucosal layer. A total of 79 lesions (25.2%) were located beyond the reach of the sigmoidoscope (at the transverse colon, ascending colon or cecum). The sensitivity of the IFOBT, as calculated based on the 281 cases to which one-time RPHA was simultaneously applied, was 40.1%. Regarding the tumor invasion depth, 27.1% of the cases were found to have intra-mucosal cancer, 41.5% had invasive cancer within the sub-mucosal layer and 79.7% had invasive cancer beyond the sub-mucosa.
Conclusion: SCS detected a significantly higher number of colorectal cancers than the IFOBT. We recommend adding SCS as an official optional method of screening for colorectal cancer in Japan.
