Clinical Question

How acceptable are various colorectal cancer screening modalities, and what is the yield in population-based screening programs?

Bottom Line

Based on the initial round of screening in this randomized trial, it appears that more patients complete fecal immunochemical testing (FIT) than colonography or colonoscopy. Using the most conservative estimate, the yields of advanced adenomas and advanced neoplasms are similar. If considering only those participants who were actually screened (not the total number invited to participate), colonoscopy found more of these lesions but also had the lowest participation rate. (Level of Evidence = 2b)

Synopsis

These researchers assigned 16,087 patients to one of four screening approaches: three cycles of FIT every two years (n = 9,739), a single reduced-preparation computed tomographic colonography (n = 2,617), a single full-preparation computed tomographic colonography (n = 2,625), or a single colonoscopy (n = 1,106). The participants were all residents of a single region in Italy, were between 55 and 64 years of age, and had not had recent colorectal cancer screening. If a FIT result or any of the colonography results were abnormal, the patients were invited to have colonoscopy. One of two experienced pathologists evaluated all the colorectal lesions; the paper does not report if they were aware of allocation. The researchers classified lesions as follows: hyperplastic polyp; or serrated, tubular, tubulovillous, or villous adenoma or adenocarcinoma. Additionally, they defined advanced adenoma as being greater than 9 mm or with more than 20% villous histologic component or with severe dysplasia (or any combination of these). They also defined advanced neoplasia as cancer or advanced adenoma. Finally, to avoid differential participation in the program, spouses were clustered to the same screening modality.

This paper presents data from the first screening round. Slightly more than one-half of the patients were women and slightly less than one-half were of low socioeconomic status; the average age was 59 years. Among the invitees, one-half completed the first round of FIT, approximately 25% completed each of the two colonography modalities, and approximately 12% completed the colonoscopy. Keep in mind that the FIT group still has two more cycles to complete, so the participation rate for the whole study is likely to be much lower. The findings depended on the denominator. First, regardless of denominator, they found only 20 cancers. If you look at everyone who was invited, approximately 1% of the time the modalities detected advanced adenomas and advanced neoplasms. Among the 6,116 participants who were actually screened, however, the numbers look different. FIT identified advanced adenomas and advanced neoplasms slightly less than 2% of the time, whereas the various colonographies found them approximately 5% of the time and colonoscopy 7% of the time. A downside to colonography is the age-old bane of clinicians: 5% of the time, radiologists identified extracolonic findings outside the area of interest that were of uncertain importance and were likely to boost the cost without improving outcomes.

Study design: Randomized controlled trial (nonblinded)

Funding source: Government

Allocation: Uncertain

Setting: Population-based

Reference: SaliLMascalchiMFalchiniMet alSAVE study investigatorsReduced and full-preparation CT colonography, fecal immunochemical test, and colonoscopy for population screening of colorectal cancer: a randomized trial. J Natl Cancer Inst2015;108(2):djv319.