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Flat adenomas exist in asymptomatic people: important implications for colorectal cancer screening programmes.

ABSTRACT: BACKGROUND: Flat adenomas are non-exophytic with a flat top or central depression and histologically the depth of dysplastic tissue is never more than twice the mucosal thickness. Flat adenomas frequently contain severely dysplastic tissue, and may progress rapidly through the adenoma-carcinoma sequence. Flat lesions have never been described in a British asymptomatic population. AIMS: To determine whether flat adenomas exist in an asymptomatic population participating in a large randomised controlled trial of flexible sigmoidoscopy screening. PATIENTS: A total of 3000 subjects (aged 55-64 years) underwent screening by flexible sigmoidoscopy. METHODS: All polyps were removed and sent for histology. The number of polyps with endoscopic and histological features of flat adenomas was recorded. RESULTS: Three subjects had a total of four flat lesions--that is, one per 1000 people screened. Three contained severely dysplastic tissue, one a focus of adenocarcinoma. Three of the four lesions were less than 5 mm in size and the fourth was 15 mm in diameter. CONCLUSIONS: Flat lesions with severe dysplasia exist in the asymptomatic population. This has major implications for gastroenterologists who should be trained to identify them. Their existence is of importance to molecular biologists and epidemiologists investigating the aetiology of colorectal cancer.

SUBMITTER: Hart AR

PROVIDER: S-EPMC1727201 | biostudies-other | 1998 Aug

REPOSITORIES: biostudies-other

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Project description:ObjectivesTo assess detection rates for colorectal cancer (CRC) and advanced adenomas in asymptomatic CRC screening participants and bowel symptoms in association with CRC and advanced adenoma.DesignCross-sectional study.SettingTwo screening centres.Participants42 554 men and women, aged 50-74 years, participating in a randomised CRC screening trial. 36 059 participants underwent a sigmoidoscopy (and follow-up colonoscopy if positive sigmoidoscopy) and 6495 underwent a colonoscopy after a positive faecal immunochemical test (FIT).Primary and secondary outcome measuresProportion of asymptomatic participants diagnosed with CRC or advanced adenomas. Prevalence of bowel symptoms (rectal bleeding, change in bowel habits, diarrhoea, constipation, bloating, alternating bowel habits, general symptoms, other bowel symptoms) recorded by the endoscopist and their association with CRC and advanced adenomas.ResultsAmong sigmoidoscopy participants, 7336 (20.3%) reported at least one symptom. 120 (60%) out of 200 individuals with screen-detected CRC and 1301 (76.5%) out of 1700 with advanced adenoma were asymptomatic. Rectal bleeding was associated with detection of CRC and advanced adenoma (OR 4.3, 95% CI 3.1 to 6.1 and 1.8, 95% CI 1.5 to 2.1, respectively), while change in bowel habits only with CRC detection (OR 3.8, 95% CI 2.4 to 6.1). Among the FIT positives, 2173 (33.5%) reported at least one symptom. Out of 299 individuals with screen-detected CRC and 1639 with advanced adenoma, 167 (55.9%) and 1 175 (71.7%) were asymptomatic, respectively. Detection of CRC was associated with rectal bleeding (OR 1.8, 95% CI 1.4 to 2.3), change in bowel habits (OR 2.2, 95% CI 1.4 to 3.5) and abdominal pain (OR 1.8, 95% CI 1.2 to 2.7).ConclusionsSome bowel symptoms increased the likelihood of being diagnosed with CRC or advanced adenoma. However, the majority of individuals with these findings were asymptomatic. Asymptomatic individuals should be encouraged to participate in CRC screening.Trial registration numberClinicaltrials.gov Identifier: NCT01538550.