Frequency of early colorectal cancer in patients undergoing colonoscopy

Early colorectal cancer is defined as carcinoma limited to the mucosa or submucosa. Up to 20 per cent of all colorectal cancers treated in some Japanese institutions are early cancers. These cancers are sometimes flat or depressed, and may be less than 1 cm in diameter. The aim of this study was to identify the frequency and morphology of early colonic cancers detected at colonoscopy by a surgeon aware of and looking for such lesions.

A review was made of all colonoscopies performed by or under the supervision of a single endoscopist between 1990 and 1998. Follow-up and outcome of all patients with early colorectal cancer was undertaken.

Ninety-five invasive colorectal cancers were identified from 2198 colonoscopies. Eighteen were early colorectal cancers (T1). Macroscopically these were flat (nine tumours), villous (four) and pedunculated (five). Two patients had lymph node metastasis. The median size of flat cancers was 20 (range 9-30) mm. Median follow-up was 3 years. One patient had local recurrence, and another, whose early cancer was metachronous, died from metastatic cancer.

This study identified early colonic cancer with similar frequency and morphology to that reported by the Japanese. Colonoscopy should be considered as the investigation of choice for patients with large bowel symptoms.