METACHRONOUS ADVANCED NEOPLASIA RATES IN PATIENTS WITH ISOLATED SESSILE SERRATED LESIONS (SSLS) VERSUS THOSE WITH SSLS WITH CONCOMITANT SMALL TUBULAR ADENOMAS

Background/Aims:
Current guidelines for post-polypectomy surveillance colonoscopy for small sessile serrated lesions (SSLs) are based on low quality of evidence. At present it is recommended to have a follow-up colonoscopy in 5-10 years if 1-2 small SSPs are found on index colonoscopy, 3-5 years for 3-4 small SSLs, however these are all weak recommendations (per US Multi-Task Force 2020 guidelines). It is not well defined if small tubular adenomas (TA) found in conjunction with SSLs should be considered as an additive risk for Metachronous advanced neoplasia (MAN).

We aimed to compare the rate of MAN on surveillance colonoscopy in patients with isolated SSLs versus mixed SSLs that is SSLs found with small TA.

Methods:
Colonoscopy data was retrieved for 1478 patients found to have SSL on pathology records from 2015 to 2023 at two academic tertiary care hospitals (University of Arizona Banner Tucson Campus and South Campus). Exclusion criteria included: lack of repeat surveillance colonoscopy after initial index colonoscopy, traditional serrated adenomas, prior colorectal cancer, inadequate bowel preparation in either the index or subsequent colonoscopy, inflammatory bowel disease, and polyposis syndromes. 210 patients met study criteria and were stratified into 4 groups: small <10mm isolated SSL, small mixed SSL <10mm (with concomitant small TAs), large isolated SSLs, and large mixed SSPs (with concomitant TAs). The rate of total MAN on surveillance colonoscopy (our primary endpoint) was then compared between groups. Secondary endpoints were also analyzed, including: rate of polyp burden, advanced neoplasia, and any subsequent sessile serrated lesion found on surveillance colonoscopy. Rates of MAN were compared by two sided Fisher’s exact test.

Results:
Out of 210 patients that met the inclusion criteria, in aggregate there were 118 total isolated SSL and 92 total SSL found with concomitant TAs. The rate of MAN for those with mixed TA+SSL was 18.5% (17/92) which was significantly higher (p=0.0076) versus those with total isolated SSL was 5.9% (7/118). Total MAN for Mixed small (<10mm) SSL+TA was 13.6% (8/59) which was significantly higher than that for isolated small SSL 1.4% (1/76), (p= 0.0104). For patients with large SSL, 75 had SSLs greater than 10mm (42 isolated, 33 mixed). The rate of MAN with isolated large SSL was 14.3% (6/42) while in large SSL with mixed TAs was 27.3% (9/33) (p=0.25).

Conclusion:
Total MAN for small SSLs when found with mixed TAs in comparison to those with isolated SSLs is higher. Decision making for SSLs intervals should consider including the presence of concomitant small TAs as a additive risk factor for MAN. Further studies should have improved power and combine additional centers and examine how mixtures of different polyp types may compound MAN and CRC risk.