The potential of imaging in CRC screening –  Colorectal cancer (CRC) screening has been implemented in almost 40 countries to date. Some countries have chosen for fecal immunochemical testing (FIT) screening, whereas others have implemented colonoscopy screening. FIT-based screening programs have a relatively high population uptake, but the FIT test has low sensitivity. In contrast, colonoscopy has a high sensitivity, but low population uptake, due to the invasiveness of the procedure. Both FIT and colonoscopy screening seem to be suboptimal choices. However, there may be an alternative to these forms of screening.

The potential of imaging in CRC screening

CRC screening by means of imaging may be a suitable alternative to both FIT and colonoscopy screening. It enables external inspection of the colon and is therefore less invasive than colonoscopy. It follows that population uptake will probably be higher than for colonoscopy. Furthermore, test characteristics of imaging for CRC and large precursor lesions are reasonable, compared to colonoscopy.

To explore the potential of imaging techniques in CRC screening Marjolein Greuter et al. performed a simulation study using our existing ASCCA model.

Read more about the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model

Study design

Using the ASCCA model, several imaging strategies were simulated. Strategies differed in imaging test used, screening intervals and the number of screening rounds. Both CT colonography (CTC) and MR colonography (MRC) were simulated. The comparator strategies were no screening, three rounds of ten-yearly colonoscopy screening and eleven rounds of biennial FIT screening. For each screening strategy under evaluation, observed participation rates from Dutch implementation trials were used.

Screening test	Number of screening rounds	Screening interval	Start age of screening	Participation rate
CTC	2	10	55	34%
	3	10	55
	4	10	50
	5	5	55
MRC	2	10	55	34%
	3	10	55
	4	10	50
	5	5	55
Colonoscopy	3	10	55	22%
FIT	11	2	55	63%

Results

According to our model predictions

• All imaging strategies were more effective and less costly than no screening.
• CTC screening was favored over MRC screening due to the lower costs per test.
• Compared with three rounds of colonoscopy screening, CTC with five rounds was found to be cost-effective in an incremental analysis of screening strategies.
• Imaging was not a cost-effective alternative to FIT screening.

Life-years gained

The figure shows a cost-effectiveness plane depicting incremental life-years gained (LYG) (x-axis) against incremental costs (y-axis) for CT colonography (CTC), MR colonography (MRC), colonoscopy and faecal immunochemical test (FIT) screening compared to no screening (origin). Darker colours indicate more screening rounds (two, three and four rounds with a 10-year screening interval) and the open symbol indicates the imaging strategies with five screening rounds with a 5-year interval.

 

Take home message

CTC and MRC have potential for CRC screening compared with no screening and three rounds of colonoscopy screening. Compared with FIT screening, imaging-based screening is unlikely to be ever cost-effective. Read full article.