Colorectal Cancer Screening and Early Detection

Colorectal cancer (CRC) remains a major health issue in the United States and throughout the world. In the United States in 2010, there will be nearly 150,000 new patients diagnosed, and approximately 48,000 deaths will be attributed to this disease. Worldwide, close to 1,000,000 new cases will be diagnosed, resulting in 500,000 deaths. As our regular followers of the journal know well, I normally review the important topic of screening and early detection of CRC in the month of March, which is Colorectal Cancer Awareness Month. However, with this issue being published in April, I thought that it would be an appropriate time for me to review this subject. In 2010, there are several screening methods that are recommended by the American Cancer Society, the U.S. Multi-Society Task Force, the U.S. Preventive Services Task Force, and the American College of Radiology. The five main screening modalities include fecal occult blood test (FOBT) with unrehydrated Hemoccult II, annual immunochemical FOBT, sigmoidoscopy every 5 years, annual Hemoccult II in combination with sigmoidoscopy every 5 years, or colonoscopy every 10 years. Prior to 2001, FOBT and sigmoidoscopy were the most widely used screening modalities for the general population. However, in July 2001, Medicare initiated coverage for screening colonoscopies, and since then, colonoscopy has become the most widely used test, with a dramatic reduction in the number of flexible sigmoidoscopies being performed. Virtual colonoscopy, also known as computed tomography (CT) colonography, is being increasingly used as a screening method. One of the main advantages of this modality is that it is noninvasive and does not require sedation. In contrast to colonoscopy, the procedure is done relatively quickly, within 15-20 minutes, and because sedation is not required, patients are able to resume their normal activities shortly after the testing is completed. While this screening method has many advantages, it has not been uniformly recommended in the CRC screening guidelines, perhaps in large part because it misses lesions that are less than 1 cm in size, and perhaps more importantly, positive findings still require the individual to undergo colonoscopy for biopsy and/or removal of any lesions. Two other screening methods that have received a great deal of attention but are not yet ready for daily use include stool DNA testing and video capsule. Without question, however, colonoscopy remains the gold standard screening method as it can directly visualize the presence of polyps, remove polyps when detected, and in so doing, facilitate the removal of the main risk factor for cancerous growth and potentially identify the presence of early-stage colon cancers. Why is CRC screening and early detection so important? In terms of sporadic CRC, we know that tumors arise from adenomatous polyps, which generally take 8 to 12 years to transform from a polyp into true cancer. The removal of any visualized polyp would therefore remove the etiology for CRC. In this way, CRC screening is an effective strategy in preventing the development of cancer. When diagnosed in its earliest stages, nearly 90% of patients with CRC will be cured of their disease. However, when CRC screening is not done, the disease usually presents in a more advanced stage with the potential for metastatic spread. In this setting, the overall prognosis remains poor with most patients being incurable. While metastatic CRC (mCRC) is now becoming a chronic disease with the use of several lines of therapy yielding median overall survivals in the 24-28–month range, the overall 5-year survival remains at less than 10%, and patients eventually succumb to this disease. What are the recent trends in the use of CRC screening? The good news is that there has been a slow and steady upward trend in CRC screening rates over the past 10 years. In the late 1990s, the overall screening rates were in the 20%-30% range. In reviewing the most recent data on CRC screening modality trends published in 2008, nearly 55% of individuals in the United States over the age of 50 years are undergoing screening, While this is positive news, the sobering fact is that 45% of eligible individuals in the United States, which equates to millions of people, are not screened by any method, let alone the gold standard of colonoscopy. Women appear to undergo screening less frequently than men, as there is a common misperception that women are at reduced risk for developing CRC than their male counterparts, despite the fact that colon cancer incidence is the same for males and females. There are also differences in screening rates across racial and ethnic groups in that African-Americans and Hispanics are much less likely to be screened than whites, and among Asians, individuals from Korea are less likely to undergo screening than those from other Asian countries. When socioeconomic issues are factored into the equation, the differences are much less pronounced. Clearly, creative outreach and awareness programs are required to improve screening rates across racial and ethnic groups. One question to consider is whether CRC screening is costeffective. It is now well-established that screening is able to Editorial