CRC screening - what with & when. Confused?

Colorectal cancer (CRC) is a common cancer worldwide. In the United States, CRC is the third most common cancer and is the second leading cause of cancer death. In 2008 it is estimated that a total of 148,810 cases will be diagnosed and 49,960 people will die of CRC in USA. Screening for CRC is one effective way of detecting the cancer earlier and thus leading to better outcome and lives saved. It is estimated that effective CRC screening in USA could lead to 18,800 lives saved per year.

The US Preventive Services Task Force (USPSTF) recently updated its recommendations on CRC screening. The USPSTF has now stated that screening should start at 50 years of age and stop at 75 for individuals who have a consistent history of negative screening results. (More than 80% of CRC cases occur in patients older than 55.) In addition, screening should stop in all adults older than 85 years. It also recommends that the screening methods should be performed with high-sensitivity faecal occult blood testing (HS-FOBT), sigmoidoscopy with FOBT and colonoscopy. The USPSTF recommends that screening should be done with HS-FOBT annually or sigmoidoscopy every 5 years with HS-FOBT every 3 years or screening colonoscopy every 10 years. (HS-FOBT refers to the high-sensitivity guaiac testing or the faecal immunochemical test. All patients with positive HS-FOBT require a subsequent colonoscopy.) The lead author of the USPSTF recommendations stated that “Life years saved is just about the same for the 3 different approaches to screening. You can choose from these 3”. The USPSTF is also not recommending CT colonography (CTC) and faecal DNA testing as screening tools. The arguments against CTC include the following. (1) Uncertainties about radiation risk and CTC, especially with repeated screenings over time. The risk of radiation exposure leading to the development of cancer has been estimated as 1 per 1000. (2) Somewhere between 1 in 3 to 1 in 8 patients who undergo CTC will need subsequent colonoscopy to confirm, refute or treat the underlying problem.  (3) Up to 16% of patients will need additional testing for follow-up of incidental findings outside the colon; the implications of these findings are still not clear. (Performing CTC can also lead to colonic perforation. The incidence of perforation is estimated to be 0.9 to 6 per 10, 000 studies. This compares with 3.8 perforations per 10,000 colonoscopies.)

In USA, there is another learned body called the American Cancer Society-US Multi-Society Task Force (ACS-MSTF) which issues recommendations on CRC screening as well. (The ACS-MSTF is commissioned by the American Cancer Society and issued jointly by professional societies representing gastroenterology and radiology.) The ACS-MSTF recommends both CTC and faecal DNA testing as screening tools. However, it did not recommend a specific age for cessation of CRC screening.

For the public, the differences in the recommendations from both task forces can lead to confusion and angst. To help with the situation, I think it is important for Joe Public to bear in mind the following points.  (1) CRC screening has been proven to save lives. (2) The gold standard for CRC screening is still colonoscopy and FOBT. (3) Colonoscopy is both diagnostic and therapeutic.  (4) Screening colonoscopy should start at 50 and, for those with negative screening, subsequent screening colonoscopy is to be performed at 10 year intervals.