Editorial | June 15, 2016
Colorectal Cancer ScreeningWhich Test Is Best? FREE ONLINE FIRST
Colorectal cancer is an ideal target for population screening—it is a prevalent disease that can be detected and treated at an asymptomatic stage leading to reduced cancer mortality. Several randomized clinical trials have demonstrated mortality benefit from different screening strategies.1 With this backdrop, the National Colorectal Cancer Roundtable has announced an ambitious effort to increase to 80% the proportion of the eligible US population who are up to date with screening by the year 2018.2 However, there are multiple options available for colorectal cancer screening that vary in accuracy, interval, and harms. There is also large variation in the quality of evidence to support different tests’ effectiveness to reduce cancer mortality and substantial differences in costs. When health care outcomes among competing strategies are unclear, recommendations developed through rigorous methods such as those used by the US Preventive Services Task Force (USPSTF) may assist clinicians, patients, and payers to make informed decisions.
The USPSTF has updated its recommendations for colorectal cancer screening in the current issue ofJAMA.3 The focus has changed from the 2008 statement by removing recommendations for specific screening tests and highlighting the importance of screening with any strategy. Specifically, the 2008 recommendations included 3 strategies: fecal occult blood testing (FOBT), flexible sigmoidoscopy, and colonoscopy, while the updated recommendations include more options without designating preferred tests. The 2016 USPSTF recommendations list 7 different screening strategies including colonoscopy, fecal immunochemical testing (FIT) for occult blood, guaiac-based FOBT (gFOBT), sigmoidoscopy alone, sigmoidoscopy plus FIT, the FIT-DNA test (multitargeted stool DNA test), and computed tomography (CT) colonography (see the Table in the USPSTF recommendation statement published in JAMA).3
Based on the development of more sensitive and specific tests to detect human hemoglobin in the stool, FIT largely replaces the gFOBT strategies previously endorsed. Although the majority of clinical trials that demonstrated reduction in colorectal cancer mortality used gFOBT, it is successfully argued that using a more accurate FIT will only improve the mortality benefit from FOBT screening while reducing harms due to unnecessary follow-up colonoscopy following false-positive results. However, there is variability in the test characteristics between different FITs, and although meta-analysis estimates an overall cancer sensitivity and specificity of 79% and 94%, respectively, these range from 73% to 92% and 87% to 95%, respectively.4
Flexible sigmoidoscopy was recommended in the prior recommendations at 5-year intervals, with FOBT every 3 years. Several randomized clinical trials confirm the mortality benefit of sigmoidoscopy screening,5- 7 although Holme et al6 reported significant benefit only when FIT was added to sigmoidoscopy. The 2016 recommendations extend the sigmoidoscopy screening interval in the combined strategy to 10 years while increasing the frequency of FIT to annually. While it is difficult to exclude sigmoidoscopy from the list of recommended strategies based on the quality of evidence supporting benefit, sigmoidoscopy use in the United States has been declining—fewer than 1% of individuals reported cancer screening with sigmoidoscopy in 2012 compared with 10% who used FIT and 60% who underwent colonoscopy.8
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