YIELD OF FLEXIBLE SIGMOIDOSCOPY-BASED SCREENING FOR COLORECTAL NEOPLASIA IN GREEK AVERAGE-RISK INDIVIDUALS: IMPACT OF SERRATED POLYPS

Aims:

Flexible sigmoidoscopy (FS) is an attractive screening modality, being less invasive and costly compared to full colonoscopy. We investigated the yield of FS with respect to advanced colorectal neoplasia (ACN) detection and identified factors correlating with ACN missed by FS-based screening.

Methods:

Retrospective cross-sectional study of data from 2005 patients aged ≥50 years (57.2% female, 61.8 ± 8.2 years) who underwent an average-risk screening colonoscopy between 1/2014 – 6/2018. ACN was defined as conventional adenoma ≥10 mm, villous histology, high-grade dysplasia, sessile serrated adenoma/polyp (SSA/P)≥10 mm, SSA/P with cytologic dysplasia, traditional serrated adenoma, or cancer. The additional yield resulting from conversion to full colonoscopy in patients with pre-established distal findings (≥3 conventional adenomas, ≥10 mm, villous, or high-grade dysplasia) was also evaluated. Two definitions of FS up to the sigmoid-descending junction (FS-1) or splenic flexure (FS-2) were analyzed.

Results:

Colonoscopy revealed 419 conventional adenomas in 293 (14.6%) patients, 54 SSA/Ps in 35 (1.7%) patients and 114 ACNs in 102 (5.1%) patients. FS alone would have led to the detection of 40.4% (46/114; FS-1) and 53.5% (61/114; FS-2) cases of ACN. Forty-two (2.1%; FS-1) and 56 (2.8%; FS-2) patients with pathological distal findings would have undergone full colonoscopy, resulting in the additional detection of 8 (7%) and 7 (6.1%) ACNs, respectively. Overall, the implementation of FS-based screening would have led to the identification of 47.4% (54/114; FS-1) and 59.6% (68/114; FS-2) cases of ACN. Individuals with at least one SSA/P of any size anywhere in the colon were more likely to have proximal ACN with no concurrent distal findings that would have led to full colonoscopy [age- and gender-adjusted RR: 32.6, 95% CI 15 – 70.6, P = 0.0001 (FS-1), 42.3, 95% CI 19.2 – 93.6, P = 0.0001 (FS-2)].

Conclusions:

In Greek average-risk individuals, 40 – 53% of cases of ACN would be missed by FS-based screening. In our setting, SSA/Ps were the only identifiable factor affecting negatively the yield of FS-based screening.