More Participation Renders FIT vs CT Colonography More Efficient for CRC Detection

While repeated rounds of fecal immunochemical testing (FIT) are more effective for detecting advanced neoplasia in colorectal cancer (CRC) population screening compared with a single CT colonography, it may likely be due to differing rates of participation, according to study findings in The Lancet Gastroenterology & Hepatology.

Researchers conducted a randomized controlled trail, called SAVE (ClinicalTrials.gov Identifier: NCT01651624), to compare a single CT colonography with 3 rounds of FIT to determine which screening method yielded higher colorectal advanced neoplasia detection rates.

Of 14,981 participants included in the study, 5242 patients were randomly assigned to the CT colonography group (women, 53.6%) and 9739 to the FIT group (women, 53.5%). Participants in both groups had a mean age of 59±3.6 years.

Exclusion criteria were previous history of CRC, advanced adenoma, inflammatory bowel disease, colonoscopy within the last 5 years, receiving FIT within the last 2 years, and other severe conditions.  

A CT colonography was determined positive if patients had a colonic mass or at least one polyp that measured 6 mm in diameter or greater. Adenomas were considered advanced if the diameter exceeded 9 mm, if they had villous histology higher than 20%, or severe dysplasia.

The primary outcome was the detection rate for advanced neoplasia.

Among the patients in the colonography group, 60 patients were diagnosed with advanced adenoma and 7 were diagnosed with cancer based on histology. In the FIT study group, 164 patients were diagnosed with advanced adenoma and 22 were diagnosed with cancer.

The modified intention to treat analysis showed that the detection rate of advanced neoplasia after 3 rounds of FIT was higher than the rate for CT colonography (2% [95% CI, 1.1-1.8] vs 1% [1.7-2.3]; P =.0094). However, in the per protocol analysis, the detection rate of advanced neoplasia was significantly higher in the CT colonography group compared with the FIT group after 3 rounds (5.2% [4.1-6.6] vs 3.1% [2.7-3.6]; P =.0002).

In the per protocol analysis, there was no significant difference between the proportion of patients who tested positive and referred to additional screening in the CT colonography group (n=129) and the FIT group (n=700).

The modified intention to treat analysis showed that the referral rate for additional screening was significantly lower in the CT colonography group compared with the FIT group after 3 rounds (P <.0001).

The positive predictive value for detection of advanced neoplasia was higher in the CT colonography group (P <.0001).

Study limitations include the exclusion of participants over the age of 70 and the lack of quality assurance for CT colonoscopy.

“The opposing results of the modified intention-to-screen and per-protocol analyses are remarkable; however, they can be explained by considering the key role of participation, which was significantly higher for FIT than for CT colonography, and justifies the overall increased pick-up of advanced neoplasia,” the study authors noted.