| [ Summary ] |
The effectiveness of flexible sigmoidoscopy (FS) has been demonstrated in randomized controlled trials (RCTs). A meta-analysis of four RCTs showed that one-time FS reduced the risk of colorectal cancer (CRC) mortality by 46 % in overall CRC and by 66 % in distal colon cancer. Moreover, the morbidity risk was reduced by 35 % in overall CRC and by 49% in distal colon cancer. However, no risk reduction was observed in both mortality and morbidity rates of proximal colon cancer. The effectiveness of FS has been observed for more than 10 years. Recent observational studies using total colonoscopy (TCS) have shown a reduced risk of mortality and morbidity in distal and proximal colon cancers. However, TCS is less effective in proximal colon cancer than in distal colon cancer. In the US, TCS is performed once every 10 years as the main CRC screening method. In the UK, FS is performed only once when people turn 55 years of age, and then a fecal occult blood test (mainly fecal immunochemical test) is performed biennially as the main CRC screening method. Therefore, the CRC mortality rate has gradually decreased in both these countries. Japan should also introduce an organized population-based endoscopic screening initiative to reduce the CRC-associated mortality rate in Japan. |