PTH-96 Colorectal cancer diagnosed at sigmoidoscopy, is colonoscopy necessary to assess for synchronous cancer?

Abstract

<h3>Introduction</h3> The Association of Coloproctology of Great Britain &amp; Ireland (ACGBI) 2017 colorectal cancer (CRC) guidelines reaffirmed the longstanding practice of assessing for synchronous cancer in patients diagnosed with CRC at sigmoidoscopy (f-sig). Ideally by colonoscopy in addition to CT staging of chest, abdomen &amp; pelvis (CT CAP), or alternatively CT colonography (CTC) and CT thorax if complete colonoscopy not possible. In the literature, approximately 3.5% of patients had synchronous CRC. Scheduling colonoscopy may delay treatment and be onerous for patients. Access to prompt colonoscopy can be challenging due to capacity issues, especially in the COVID-19 pandemic era. <h3>Methods</h3> Data were retrospectively analysed from electronic endoscopy, radiology and pathology records from patients diagnosed with CRC at f-sig and colonoscopy over 11 years (2010-2020 inclusive). <h3>Results</h3> Analysis 1: 680 patients who had CRC diagnosed at f-sig: 230 underwent pre-treatment colonoscopy (33.8%). Interval between f-sig and colonoscopy; mean 17.5 days/ median 15.0 days. Two synchronous cancers identified at colonoscopy; 0.9% 1. 57 years old man with primary rectal cancer and synchronous transverse colon cancer – both lesions reported on staging imaging scans. • 69 years old woman with a primary rectal cancer and synchronous sigmoid colon cancer (not seen at f-sig due to poor preparation) – both lesions reported on staging imaging scans. Analysis 2: 796 patients who had CRC diagnosed at colonoscopy: 48/796 have a significant 2nd finding (6.0%) • 24 had synchronous CRC (3.0%)/24 had a significant polyp &gt;20 mm (3.0%) In these 48 cases, if F-sig was performed instead of colon, what would have been the outcome? • Only in one case would a significant lesion be missed. 72 years old man with a primary rectal cancer and a 30 mm ascending colon polyp (not seen on staging CT scan). • In the other 47 cases; staging CT scans pick up lesions or metastases, or lesions are all left sided and would be seen at F-sig, or lesions are all right sided and would not be seen at f-sig, or missed lesion was a benign polyp. <h3>Conclusions</h3> This is a large analysis of 1476 patients diagnosed with CRC. Of the 796 diagnosed at colonoscopy, 6.0% had a synchronous lesion (48 patients), 3.0% had a synchronous CRC, only 1 patient would have had a missed lesion if they’d had a f-sig alone. Of the 680 patients diagnosed with CRC at f-sig, 230 had a colonoscopy (33.5%), the rest were precluded due to advanced disease/obstruction or weren’t fit due to advanced age/co-morbidity. Colonoscopy was undertaken at a median of 15.0 days. The yield of identifying a synchronous cancer at colonoscopy in this cohort is &lt; 1%, in both cases these lesions were reported on staging imaging scans. British Society of Gastroenterology and ACPGBI guidelines from 2019 suggest that in patients who are fit/suitable they should undergo a surveillance colonoscopy at 12 months post CRC diagnosis. Given the capacity issues affecting colonoscopy services in the pandemic era, a proposed pathway for patients diagnosed with CRC at sigmoidoscopy; if staging imaging scans shows resectable CRC without synchronous lesion, is to consider undergoing surgery and to utilise 12-month colonoscopy to clear any adenomas. Alternatively CTC and CT thorax could be utilised though capacity issues may limit this approach. This data supports the consideration of alternative approaches as the likelihood of a synchronous cancer not seen at sigmoidoscopy and staging imaging scan appears to be very low.