Why screen for colorectal cancer?

Abstract

Colorectal cancer (CRC) is the third most common cancer in men and the second in women in the world. Although there is a wide geographic variation in CRC incidences with higher incidences in more developed regions, the CRC incidences are also rising rapidly in many Asian countries. In Hong Kong, colorectal cancer has already surpassed lung cancer as the most prevalent cancer. Unlike many other cancers, CRC has a very well recognized precursor lesion, namely adenoma, which makes early detection and removal possible. High quality data from previous trials have confirmed that screening of CRC could reduce the incidence and mortality related to CRC. The simple fecal occult blood test (FOBT) has been shown to reduce cancer mortality by 15-30%. As yet, data on the more sensitive and specific fecal immunochemical test (FIT) are lacking but it is anticipated to be superior to FOBT. Flexible sigmoidoscopy has also been shown in randomized controlled studies to reduce CRC mortality by about 47% but this reduction is limited to distal cancer. On other hand, colonoscopy has been found to reduce CRC mortality by about 68%. Notably, the cancer mortality reduction is also higher for distal than proximal CRC. Despite all the benefits of CRC screening, there are also drawbacks such as potential complications related to screening and the cost of screening. The highest complications and cost are expected with the use of screening colonoscopy. However, cost-effectiveness study still showed that among various screening strategies, colonoscopy is associated with the highest life years gained, highest number of CRC prevented and the lowest total costs. There are overwhelming evidences to support that CRC screening can reduce the incidence and mortality of CRC. Whilst CRC is rapidly emerging in Asian countries, the adoption of a national CRC screening program is urgently needed.