Detection of High-Risk Sessile Serrated Lesions: Multi-Target Stool DNA Versus CT Colonography

Background: The serrated pathway for colorectal cancer (CRC) development is increasingly recognized. Patients with sessile serrated lesions (SSLs) that are large (≥10 mm) and/or have dysplasia (i.e., high-risk SSLs) are at higher risk of progression to CRC. Detection of SSLs is challenging given their predominantly flat and right-sided location. The yield of non-invasive screening tests for detection of high-risk SSLs is unclear. Objective: The aim of this study was to compare non-invasive screen detection of high-risk SSLs between the multi-target stool DNA test (mt-sDNA; Cologuard) and CT colonography (CTC). Methods: This retrospective study included 7974 asymptomatic adults (4705 women, 3269 men; mean age 60.0 years) who underwent CRC screening at a single center by mt-sDNA (Cologuard) from 2014-2019 (n=3987) or by CTC from 2009-2019 (n=3987). Clinical interpretations of CTC examinations were recorded. Subsequent colonoscopy findings and histology of resected polyps were also recorded. Chi-square or two-sample t tests were used to compare results between mt-sDNA and CTC using 6-mm and 10-mm thresholds for test positivity. Results: The overall colonoscopy referral rate for a positive screening test was 13.1% (522/3987) for mt-sDNA versus 12.2% (487/3987; p=.23) and 6.5% (260/3987; p<.001) for CTC at 6-mm and 10-mm thresholds, respectively. The PPV for high-risk SSLs was 5.5% (26/476) for mt-sDNA, versus 14.4% (66/457; p<.001) and 25.9% (63/243; p<.001) for CTC at 6-mm and 10-mm thresholds, respectively. The overall screening yield of high-risk SSLs was 0.7% (26/3987) for mt-sDNA versus 1.7% (66/3987; p<.001) and 1.6% (63/3987; p<.001) for CTC at 6-mm and 10-mm thresholds, respectively. Conclusions: CTC at 6-mm and 10-mm thresholds had significantly higher yield and PPV for high-risk SSLs compared with mt-sDNA. Clinical Impact: The significantly higher detection of high-risk SSLs by CTC than by mt-sDNA should be included in discussions with patients who decline colonoscopy and opt for noninvasive screening.

Noninvasive strategies for colorectal cancer screening: opportunities and limitations

PURPOSE OF REVIEW

In the United States, only 67% of patients are up to date with colorectal cancer (CRC) screening. While colonoscopy is highly sensitive and specific for CRC and precursor lesion detection and removal, it is invasive, expensive and resource heavy. Hence, there is an unfulfilled need for multiple modality CRC screening that can improve current CRC screening rates and may be resource effective strategies when used in conjunction with a colonoscopy program. Our review highlights the complementary, often underutilized, noninvasive CRC screening methods with a focus on performance, risks, benefits, and recent updates.

RECENT FINDINGS

Studies demonstrate that fecal immunochemical testing (FIT) is superior to guaiac-based fecal occult blood tests for CRC screening. Studies show superiority of multitarget stool DNA test to FIT in sensitivity, though with concern for decreased specificity in setting of one-time tests. Technical advances continue to improve accuracy of colon capsule endoscopy. There are ongoing studies to characterize often difficult-to-detect high-risk lesions in computed tomography colonography. Septin 9 continues to have suboptimal accuracy for CRC screening, but has been shown to be associated with more advanced, invasive CRC stages.

SUMMARY

There are ongoing advances in noninvasive screening modalities for CRC; these should be considered as alternatives to colonoscopy in specific patient populations.