The presence of large, serrated polyps was associated with a greater risk of colorectal cancer than any other factor, including age, sex, size of adenomas, and number of adenomas, reported Dr. Sakiko Hiraoka and colleagues in an article appearing in the November issue of Gastroenterology.
Moreover, the cancers in patients with large serrated polyps were more than twice as likely to be proximal as opposed to distal, the authors reported (Gastroenterology 2010 November [doi:10.1053/j.gastro.2010.07.011]).
Dr. Hiraoka of the department of gastroenterology and hepatology at Okayama University, Japan, and colleagues performed a database study including 10,199 patients who had their first colonoscopy at Dr. Hiraoka’s institution or at 1 of 14 affiliated hospitals between June 2005 and May 2008.
Patients had to have no prior history of resection, no prior diagnosis of inflammatory bowel disease, and no familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer.
The mean age was 58.9 years, with 51.5% being male. Overall, 8.6% of the 10,199 patients were having a standard screening colonoscopy, while 41.5% underwent colonoscopy secondary to a positive fecal occult blood test. Another 20.6% had the colonoscopy because of abdominal symptoms, 13.2% due to rectal bleeding, and 2.4% because of anemia or another reason.
In the cohort, there were a total of 1,573 patients (15.4%) with advanced neoplasia, including 708 (6.9%) with colorectal cancer and 140 (1.4%) with large serrated polyps.
Dr. Hiraoka and colleagues found that out of several known risk factors for colorectal cancer, the presence of large serrated polyps carried the greatest risk, with an odds ratio of 3.34 (P less than .0001). The next-highest risk among the variables studied was age of 65 years or older (OR 2.63; P less than .0001).
Having four or more adenomas on colonoscopy carried an OR of 1.65 (P less than .01), and having an adenoma greater than 10 mm carried an OR of 1.56 (P less than .001).
Male gender did not carry any significant increased risk in this analysis.
The authors then looked at the predictors of advanced neoplasia and cancer according to location, "since clinical and biological differences have been shown recently to exist between colorectal neoplasia in the proximal and distal colon," they wrote.
Dr. Hiraoka and colleagues found that large serrated polyps were more than twice as likely to develop into proximal colon cancer than into distal colorectal cancer (OR for proximal cancer, 4.79; P less than .0001; OR for distal colorectal cancer, 2.23; P less than .01).
The correlation between serrated polyps and proximal cancer may be a manifestation of common molecular backgrounds between them, including BRAF mutation, according to the authors.
However, it does not follow that large serrated polyps necessarily progress into colorectal cancers themselves. "In fact, CRCs which develop in [hyperplastic polyposis syndrome] patients are largely microsatellite stable rather than [microsatellite instability-high] MSI-H, suggesting that serrated polyps do not always progress into MSI-H cancer," they commented.
The authors noted that one advantage of their study was the "relatively large" proportion of patients with colorectal neoplasia.
However, they noted that their study did not involve correlating neoplasia with the specific type of serrated polyp (including hyperplastic, sessile serrated adenoma, traditional serrated adenoma, and mixed serrated polyp), which was a limitation.
Dr. Hiraoka and colleagues disclosed no conflicts of interest related to this study.