1129 Increased Risk of Sessile Serrated Adenomas on Initial Screening Colonoscopy in Post-Bariatric Surgery Patients

Abstract

INTRODUCTION: An increased standardized incidence ratio of colorectal cancer (CRC) with longer follow-up intervals after bariatric surgery has been suggested in a large retrospective Swedish cohort study. By impacting epigenetic modifications versus de novo chromosomal mutations, the complex physiologic changes following bariatric surgery may preferentially modulate CRC risk via the sessile serrated adenomas (SSAs) pathway or conventional adenoma-carcinoma sequence, respectively. Our aim was to examine the risk of CRC precursors in post-bariatric surgery patients as compared to the general population. METHODS: We conducted a single center retrospective case-control study of patients age 40 to 50 at time of bariatric surgery between 2007-2019 with subsequent documented initial screening colonoscopy and pathology. Diagnostic colonoscopy or patients with a family history of CRC (1st-degree relative age< 60 years, or two 1st-degree relatives) were excluded. 88 patients met both inclusion and exclusion criteria. Cases were matched 1:1 by age ± 2 years and gender to controls with BMI ≥ 25 undergoing average-risk screening colonoscopy during the same time period. RESULTS: Among cases, bariatric procedures consisted of Roux-en-Y (51%), laparoscopic gastric band placement (28%), and vertical sleeve gastrectomy (20%). Mean BMI pre-surgery was 42 kg/m2 compared to 33 kg/m2 at their initial screening colonoscopy (Table 1). Average time from surgery to colonoscopy was 4.5 years (SD 2.5 years), with 45% undergoing colonoscopy ≥ 5 years post-surgery. There was no significant difference in adenoma detection rate or BMI at time of colonoscopy between surgical and control groups. SSA detection rate was significantly higher in post-surgery patients (9.1%) compared to controls (3.9%, P < 0.01). Of all detected adenomas, SSA proportion was significantly higher in surgical (15%) vs. control patients (8.2%, P = 0.03). Rectal adenomas were more common in the surgical vs. control groups (12.3% vs 3.0%, P < 0.01), but otherwise we observed no difference in the proportion of adenomas by anatomic location or advanced adenomas. Neither group had high-grade dysplasia or CRC. CONCLUSION: SSAs are more common among average-risk post-bariatric surgery patients compared to average-risk non-surgical controls. By anatomic location, adenomas are more common in the rectum compared to non-surgical controls, but the overall distribution of adenomas was similar. Further studies are needed to understand the risk of CRC following bariatric surgery.