Abstract IA14: Decision analysis for colorectal cancer screening recommendations
Authors: Zauber Ann G. 
Published: March 2017

In 2016 the United States Preventive Services Task Force (USPSTF) updated their screening recommendations for colorectal cancer (CRC). In 2002 they initially recommended CRC screening for the average -risk population, but had insufficient evidence to recommend an age to begin or end screening, or to recommend any particular test or interval of testing. For their 2008 update of the 2002 recommendation, the USPSTF requested a decision analysis using two of the three CRC models funded by the NCI's Cancer Intervention and Surveillance Modeling Network (CISNET) to inform the ages to begin and end screening, and intervals of testing. Based on the evidence review and decision analysis, in 2008 the USPSTF again recommended CRC screening, this time from ages 50 through 75, and listing the following recommended strategies: colonoscopy every ten years, flexible sigmoidoscopy ever five years with intermittent fecal occult blood test (FOBT), or annual high sensitivity FOBT.

For the 2016 recommendations, the USPSTF once again requested a decision analysis from CISNET. This time, all three CRC CISNET models were used to inform the recommendation process. The models were tasked with evaluating the benefits, burden, and harms of CRC screening strategies, estimating the optimal ages to begin and end screening, and identifying a set of model-recommendable strategies that provide similar life-years gained (LYG) and a comparable balance between LYG and screening burden. Ages to begin screening included 45, 50, and 55 and ages to end included 75, 80, and 85. Screening modalities, or combinations of modalities, included seven strategies: a high sensitivity guaiac-based fecal occult blood test (gFOBT), a fecal immunochemical test (FIT), a multi-target stool DNA test that includes a FIT (FIT-DNA), flexible sigmoidoscopy (SIG), flexible sigmoidoscopy with interval gFOBT (SIG+gFOBT), flexible sigmoidoscopy with interval FIT (SIG+FIT), computed tomographic colonography (CTC), and colonoscopy. Screening intervals varied by modality. Full adherence for all strategies was assumed.

CISNET modeled 204 unique screening strategies for a hypothetical cohort of previously unscreened US 40-year-olds with no prior CRC diagnosis. Estimates of test sensitivity were based on a literature review by the Evidence Practice Center. Benefits were modeled in terms of LYG compared with no screening; burden in terms of the lifetime number of colonoscopies required; and harms in terms of the lifetime number of colonoscopy complications. Ratios of incremental burden and benefit (efficiency ratios) were also calculated per 1,000 40-year olds.

While the three CISNET colorectal cancer models differed slightly in terms of the absolute benefits and harms of screening, they yielded consistent rankings of screening strategies. Strategies with screening beginning at age 50 generally provided more LYG as well as more additional LYG per additional colonoscopy than strategies with screening beginning at age 55. There were limited empirical data to support a start age of 45. For persons adequately screened up to age 75, additional screening yielded small increases in LYG relative to the increase in colonoscopy burden. With screening from ages 50-75, 4 strategies yielded a comparable balance of LYG and screening burden and similar LYG: colonoscopy every 10 years; sigmoidoscopy every 10 years with annual FIT; CTC every 5 years; and annual FIT. Because CTC generally requires cathartic bowel preparation comparable to that required for colonoscopy, we performed an additional analysis in which we used the number of cathartic bowel preparations as the proxy for harms and burden, rather than the number of colonoscopies. With this metric, CTC was not included as a recommended strategy because its efficiency ratio (i.e., ΔCathartic Preps / ΔLYG) exceeded that of colonoscopy.

The USPSTF posted a draft recommendation statement (RS) in September 2015 for a public comment period. This draft RS made a distinction between “recommended” and “alternative” testing strategies. Recommended—included colonoscopy every 10 years, annual FIT, annual sensitive gFOBT, and flexible sigmoidoscopy every 10 years with annual FIT. Alternative—included CTC every 5 years and FIT-DNA every 3 years. However the public comments overwhelmingly found this distinction to be confusing and the USPSTF decided to modify their recommendations for clarity. The final RS dropped the “alternative” category and created a single category of “screening tests”. The top line “A” recommendation was to screen between the ages of 50 and 75, with any of the screening tests listed. The USPSTF also gave a “C” recommendation for screening between the ages of 76-85. This “C” recommendation means that screening in this age group should be an individual decision based on a patient's overall health and prior screening history. It is stated that adults in the age group who have never been screened for CRC are more likely to benefit.

Clinical questions arise in applying these new recommendations. This includes how to adequately discuss the 7 recommended screening strategies in order for patients to make an informed decision. Also clinicians need to consider how to monitor best choices for those over 75, especially those without prior screening who would benefit most from screening.

Citation Format: Ann G. Zauber. Decision analysis for colorectal cancer screening recommendations. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr IA14.