Colorectal cancer risk of flat low-grade dysplasia in inflammatory bowel disease: a systematic review and proportion meta-analysis

Background: To date, the optimal management of patients with inflammatory bowel disease (IBD) and flat low-grade dysplasia (fLGD) of the colon or rectum remains controversial. Methods: A systematic review was reported in accordance with PRISMA 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Patients diagnosed with fLGD on surveillance endoscopy were pooled from studies published between 2000 and 2020. Advanced neoplasia was defined by the presence of HGD, CRC or small bowel adenocarcinoma detected on subsequent surveillance endoscopy or from examination of resection specimens. We estimated the pooled annual incidence rate of colorectal cancer (CRC) and advanced neoplasia, and the risk factors associated with neoplastic progression. Results: We identified 24 articles and 738 IBD patients were diagnosed with fLGD on endoscopy. Two hundred thirty-six patients (32%) underwent immediate surgery with surgical specimens demonstrating CRC in 8 patients (pooled prevalence, 8.66%; 95% CI 3.58–19.46) and HGD (high grade dysplasia) in 11 patients (pooled prevalence, 13.97%; 95% CI 5.65–30.65). Five hundred-two patients (68%) underwent endoscopic surveillance with 63 patients with fLGD progressing to advanced neoplasia during endoscopic surveillance (38 HGD, 24 CRC and one patient developing small bowel adenocarcinoma). The mean duration of follow-up after fLGD diagnosis was 71 months (10.9–212). The pooled incidence of CRC and advanced neoplasia was 0.5 (95% CI 0.23–0.77) and 1.71 per 100 patient-year (95% CI 0.88–2.54) respectively. The use of corticosteroids and location of fLGD in the distal colon were significantly associated with neoplastic progression. Conclusions: This study provides a summary incidence rate of CRC and advanced neoplasia in patients with IBD and fLGD to inform surgeons’ and endoscopists’ decision-making thus reducing potential ineffective treatments. Graphical abstract: [Figure not available: see fulltext.].