P656 Clinical implications of endoscopic submucosal dissection in management of patients with ulcerative colitis-associated dysplasia

Abstract Background Colectomy has been recommended for patients presenting ulcerative colitis (UC)-associated dysplasia because of the risk of metachronous recurrence. However, it has been recently proposed that endoscopic submucosal dissection (ESD) of dysplasia, combined with subsequent surveillance, may contribute to avoiding colectomy. This study assessed clinical implications of ESD in UC-associated dysplasia. Methods We investigated 30 lesions (27 patients) of UC-associated dysplasia/cancer treated with ESD and surgery (15 ESD and 16 surgery) including a patient who underwent surgery following ESD. Among them, paraffin-embedded tissues of 15 lesions (6 cancers, 7 high-grade dysplasia: HGDs, 2 low-grade dysplasia: LGDs) and 11 surrounding mucosae were available and gene mutation analysis was performed. Indications for ESD were determined according to the criteria applied for sporadic colorectal neoplasms that are based on magnifying endoscopy. Results The median follow-up duration was 40 months. Three out of 27 patients (11%) developed metastasis. Although no serious complications, local recurrence, or metastasis occurred in 13 patients undergoing ESD, one out of them (7.7%) had metachronous colorectal cancer 3 years after ESD in the rectum, where TP53 mutation and diffuse p53 staining was found at non-dysplastic mucosae. Based on magnifying endoscopy, we underestimated the invasion depth in two cases: in a case of deeply submucosal invasive mucinous cancer, endoscopic ultrasonography exhibited thickening of the submucosal layer exclusively at the lesion. Conclusion The proposed indication for ESD in UC-associated dysplasia is that a lesion is well-demarcated and surrounding mucosa is not actively inflamed and does not exhibit diffuse p53 staining. ESD would contribute to advances in the management of UC-associated dysplasia.