EP.FRI.247 Incidence and diversity of the primary appendiceal tumours in patients presenting with acute appendicitis: Our Experience

Background Primary appendiceal tumours are rare. Our experience with the incidental primary appendiceal tumours and their histological diversity. Patients and Method Operative and pathological databases of appendicectomies for presumed diagnosis of acute appendicitis between January 2015 and December 2020 were interrogated. Clinicopathological data were collected and analysed to present the incidence of primary appendiceal tumours, histopathological diversity and outcomes. Results 1908 appendicectomies were performed over the study period. 22 patients with primary appendiceal tumours (incidence rate 1.2%) had a mean age of 45.6(15-97) years and M:F ratio of 1:1.2. Only six patients (27.3%) had appendiceal tumour suspected either before or during surgery. 91% of the patients underwent laparoscopic appendicectomy. Right hemicolectomy was performed as the first intervention and further surgical procedure in 1 and 5 patients respectively. Histological tumour types included carcinoid(10), adenocarcinoma(4), low grade appendiceal mucinous neoplasm(4) mucinous adenocarcinoma & carcinoid(1), goblet cell carcinoid(2) and dysplastic serrated polyp(1). Tumours were located at the tip(10), body(10) and base(2). Median tumour size was 13(2.0-55.0) mm. Median hospital stay was 1.5(0-25) days. The mean survival was 30.9(2.80-73.70) months. Disease related death was a 97-year-old lady with a T4 adenocarcinoma and peritoneal disease who stayed for 25 days and offered palliative supports post appendicectomy. Conclusion Primary appendiceal tumours are diverse in histological types and are of varying prognosis. Appendicectomy alone seemed to be adequate in most cases with early-stage disease. Further surgery such as right hemicolectomy was required for adenocarcinoma and other high-grade tumours.

Distinct Colon Mucosa Microbiomes associated with Tubular Adenomas and Serrated Polyps

Background: Colorectal cancer is the second most deadly and third most common cancer in the world. Its development is heterogenous, with multiple mechanisms of carcinogenesis. Two distinct mechanisms include the adenoma-carcinoma sequence and the serrated pathway. The gut microbiome has been identified as a key player in the adenoma-carcinoma sequence, but its role in serrated carcinogenesis is unclear. In this study, we characterized the gut microbiome of 140 polyp-free and polyp-bearing individuals using colon mucosa and fecal samples to determine if microbiome composition was associated with each of the two key pathways. Results: We discovered significant differences between colon mucosa and fecal samples, explaining 14% of the variation observed in the microbiome. Multiple mucosal samples were collected from each individual to investigate the gut microbiome for differences between polyp and healthy intestinal tissue, but no such differences were found. Colon mucosa sampling revealed that the microbiomes of individuals with tubular adenomas and serrated polyps were significantly different from each other and polyp-free individuals, explaining 2-10% of the variance in the microbiome. Further analysis revealed differential abundances of Eggerthella lenta, Clostridium scindens, and three microbial genes across tubular adenoma, serrated polyp, and polyp-free cases. Conclusion: By directly sampling the colon mucosa and distinguishing between the different developmental pathways of colorectal cancer, this study helps characterize potential mechanistic targets and diagnostic biomarkers for serrated carcinogenesis. This research also provides insight into multiple microbiome sampling strategies by assessing each methods practicality and effect on microbial community composition.

Simple feedback of colonoscopy performance improved the number of adenomas per colonoscopy and serrated polyp detection rate

Background and study aims High-quality endoscopy requires improvement of not only the adenoma detection rate (ADR) but also the serrated polyp (SP) detection rate and the mean number of adenomas per positive procedure (MAP +). We evaluated whether a simple feedback of colonoscopy performance improves those quality indicators using propensity-score matching. Patients and methods Eleven endoscopists were evaluated regarding colonoscopy performance including ADRs, SP detection rates, mean numbers of adenomas per procedure (MAPs), and MAPs + with their ranking in the clinic. Endoscopic performance was compared before and after the feedback. Results Colonoscopies were performed for 874 patients before the feedback and 1,272 patients after the feedback. Using propensity-score matching, 803 patients before the feedback and 803 patients after the feedback were matched. ADR after the feedback was significantly higher than that before the feedback (50.8 % and 40.8 %, respectively). MAP after feedback was significantly larger than that before the feedback (0.92 and 0.69, respectively), as well as MAP + (1.96 and 1.69, respectively). Clinically significant SP detection rate was also improved from 10.0 % to 14.9 %. Conclusions Feedback including ADR, MAP, MAP +, and clinically significant SR detection rate could improve on those quality indicators. Further studies are needed to effectively prevent colorectal cancer in colonoscopy practice.

Impact of the sessile serrated polyp pathway on predicted colorectal cancer outcomes in the CRC-AIM model.

10545 Background: Approximately 20–30% of colorectal cancers (CRC) arise from the serrated polyp pathway. The multitarget stool DNA (mt-sDNA) test has greater sensitivity to detect sessile serrated polyps (SSPs) than a leading fecal immunochemical test (FIT). However, most modeling analyses do not account for the contribution of the SSP pathway to risk of CRC. We used the CRC-AIM model to assess the impact of the SSP pathway on predicted CRC outcomes with mt-sDNA or FIT screening. Methods: A simulated cohort of average-risk US patients underwent triennial mt-sDNA or annual FIT screening from ages 50–75. The percentage of CRCs arising from the SSP pathway were modeled at 0% (base case), 20%, and 30%, with stool screening adherence based on theoretical (100%) or previously reported (mt-sDNA 71%; FIT 43%) rates. Published SSP sensitivities for mt-sDNA and FIT were used. All other model inputs were identical to CISNET models. Sensitivity analyses used screening adherence rates of 40–70%. Key outcomes were life-years gained (LYG), CRC incidence and CRC mortality per 1000 patients. Results: Including SSPs in the model demonstrated a greater loss of LYG with FIT than mt-sDNA (Table). At 100% adherence, compared with base case, modeling 20% or 30% SSP pathway CRCs resulted in a decrease of 9–15 LYG with FIT and 2–4 LYG with mt-sDNA, a decrease in CRC incidence reduction of 3.9–6.1% with FIT and 0.7–1.1% with mt-sDNA, and a decrease in CRC mortality reduction of 2.6–4.0% with FIT and 0.4–0.8% with mt-sDNA. Using previously reported adherence, compared with base case, modeling 20% or 30% SSP pathway CRCs resulted in a decrease of 13–20 LYG with FIT and 2–5 LYG with mt-sDNA, a decrease in CRC incidence reduction of 4.4–6.9% with FIT and 0.6–1.1% with mt-sDNA, and a decrease in CRC mortality reduction of 3.5–5.4% with FIT and 0.4–0.9% with mt-sDNA. Assuming reported adherence and 30% SSP pathway CRCs, mt-sDNA had 48 more LYG, 14.6% greater CRC incidence reduction, and 12.4% greater CRC mortality reduction than FIT. Assuming 30% SSP pathway CRCs, outcomes favored mt-sDNA vs FIT even after modeling equivalent adherence rates ranging from 40–70%. Conclusions: After incorporating the SSP pathway into the model, outcomes with mt-sDNA neared those of FIT at 100% screening adherence rates and surpassed FIT at more realistic reported screening adherence rates.[Table: see text]