The Natural History of Non-Polypoid Colorectal Neoplasms
Section snippets
Radiographic analysis
Matsui and colleagues12 reported a retrospective analysis of a series of colorectal cancers that were missed by double-contrast barium enema examinations. They found six depressed and seven flat lesions (41%) could be retrospectively identified as antecedent lesions that gave rise to 32 advanced cancers. The authors found that all depressed lesions developed into nonprotuberant-type advanced colorectal cancers, whereas flat or polypoid lesions had a possibility to develop into either
Colonoscopic analysis
Matsui and colleagues14 reported eight early colorectal cancers that were incidentally followed by colonoscopy. Thirty-five cases, including 14 NP-CRN as initial lesions, were reviewed. They found that NP-CRN progressed to submucosally invasive cancer, retaining its non-polypoid configuration, and some flat lesions developed depressed areas during their progression. Although the authors also estimated the speed of growth compared with polypoid and non-polypoid lesions, they could not conclude
The importance of the depressed-type NP-CRN
Matsuda and colleagues17 analyzed 6638 colorectal neoplasms, excluding advanced cancers, treated in National Cancer Center Hospital, Tokyo, Japan. There were 4471 (67%) and 2167 (33%), polypoid and non-polypoid colorectal neoplasms, respectively. Among all non-polypoid lesions, there were 178 (2.7%) depressed lesions, 109 (61%) of which were diagnosed as high-grade dysplasia or submucosally invasive cancer. Among 5538 (83%) lesions that were identified as low- or high-grade dysplasia, the
The Japan polyp study
To clarify the natural history of NP-CRN, a large cohort study focused on the detection of NP-CRN is required. Matsuda and colleagues23 reported the results of multicenter retrospective cohort study to evaluate 5-year incidence of advanced neoplasia after initial colonoscopy. The authors studied 5309 patients with a median follow-up period of 5.1 years. Endoscopists diagnosed 13 invasive cancers on follow-up within 3 years. The initial colonoscopies were performed by Japanese endoscopists who
Summary
The natural history of NP-CRN is mostly unknown. The results of small observational studies suggest that NP-CRN lesions develop into invasive cancer with minimal size expansion. Among NP-CRN lesions, depressed lesions show more aggressive behavior and frequently develop into invasive cancers compared with polypoid lesions, regardless of their low incidence. A large prospective cohort study focused on the detection of NP-CRN is currently ongoing.
References (24)
- et al.
Prevalence and distinctive biologic features of flat colorectal adenomas in a North American population
Gastroenterology
(2001) - et al.
Flat and depressed colonic neoplasms: a prospective study of 1000 colonoscopies in the UK
Lancet
(2000) - et al.
Risk for high-grade dysplasia or invasive carcinoma in colorectal flat adenomas in a Spanish population
Gastroenterol Hepatol
(2006) - et al.
Prevalence and characteristics of nonpolypoid colorectal neoplasm in an asymptomatic and average-risk Chinese population
Clin Gastroenterol Hepatol
(2009) - et al.
Retrospective radiographic analysis of nonpedunculated colorectal carcinomas with special reference to tumour doubling time and morphological change
Am J Gastroenterol
(2000) - et al.
Natural history of colorectal nonpolypoid adenomas: a prospective colonoscopic study and relation with cell kinetics and K-ras mutations
Am J Gastroenterol
(2002) - et al.
Proportion of de novo cancers among colorectal cancers in Japan
Gastroenterology
(2006) - et al.
Small flat adenoma of the large bowel with special reference to its clinicopathologic features
Dis Colon Rectum
(1985) Endoscopic mucosal resection of flat depressed type of early colorectal cancer
Endoscopy
(1993)- et al.
Flat adenomas in the United Kingdom: are treatable cancers being missed?
Endoscopy
(1998)