Participation Key When Comparing CT Colonography and FIT for CRC Screening

Three rounds of fecal immunochemical testing (FIT) is more effective for population colorectal cancer (CRC) screening compared with a single CT colonography, likely due to a higher rate of participation, the randomized SAVE trial in Italy showed.

Among over 14,000 participants in the modified intention-to-screen analysis, the detection rate for advanced neoplasia with CT colonography was significantly lower than the rate after three rounds of FIT (1.4% vs 2.0%, P=0.0094), reported Lapo Sali, PhD, of the Istituto Fiorentino di Cura e Assistenza Hospital, and colleagues.

However, in the per-protocol analysis, the detection rate was significantly higher in the CT colonography group compared with the FIT group (5.2% vs 3.1%, P=0.0002), they noted in Lancet Gastroenterology & Hepatology.

“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 [33.4% for all three rounds of FIT vs 26.7%], and justifies the overall increased pick-up of advanced neoplasia,” they wrote, citing reasons of fear of radiation, the need for face-to-face visits, and the 3-day cathartic preparation for the lower participation rate with CT colonography.

In an accompanying editorial, Thomas Mang, MD, of Medical University of Vienna in Austria, noted that,”These results confirm that in population-based screening programs, participation is a key factor for success. Thus, a test with a weaker performance can outweigh a better performing test if it is associated with higher acceptance and adherence.”

Of note, the referral rate to work-up optical colonoscopy — the secondary outcome of the trial — was significantly lower for the CT colonography group versus the FIT group after three rounds (2.7% vs 7.5%, P<0.0001) in the modified intention-to-screen analysis, while no significant difference was observed in the per-protocol analysis (10.0% vs 11.6%).

“The effect of the higher colonoscopy referral rate of FIT, including associated complications, observed in this study, and the effect of extracolonic CT colonography findings on the comparative programmatic effectiveness of the two approaches still need to be investigated,” Mang wrote. “However, simulations suggest that CT colonography is less cost-effective than FIT.”

While CRC screening is recommended for individuals ages 45 and up by the U.S. Preventive Services Task Force and the American Cancer Society, the optimal screening test and strategy have not been established, Sali’s group said.

They previously showed that a single CT colonography was superior to one round of FIT, despite nearly a 50% lower participation rate.

For the current analysis, “because the suggested rescreening interval of CT colonography is 5 years, we aimed to compare the detection rate for advanced neoplasia by CT colonography with three FIT rounds, which require approximately the same time to be completed (4 years),” they explained.

Sali and colleagues enrolled 14,981 participants and randomized them 1:2 to a single CT colonography across two Florence hospitals (62% ages 54-60, 53.6% women) or three rounds of home-based FIT every 2 years (61% ages 54-60, 53.5% women) from December 2012 to March 2018. Participants were 54 to 65 years old, and had never been screened for CRC.

Participation rates for work-up optical colonoscopy were 98% in the CT colonography group and 78-84% for the FIT group. The number of optical colonoscopies required to diagnose one case of advanced neoplasia was higher in the FIT group (3.1 vs 1.9). More cases of advanced adenoma occurred among the FIT group than the CT colonography group (164 vs 60 participants).

Three cases of bleeding were reported the FIT group following optical colonoscopy, whereas no major complications occurred in the CT colonoscopy group after screening and work-up optical colonoscopy.

Sali and team noted that people over age 65 were not included in the study, which was a limitation. Moreover, quality assurance was not applied to CT colonography.