Incomplete polyp removal and failure to have a follow-up colonoscopy within five years after the detection of the first polyp are more strongly associated with an increased risk of developing colorectal cancer than the characteristics of the polyp, according to the results of a study published in the Annals of Internal Medicine.
Colorectal cancer is the second leading cause of cancer death in the United States. Colorectal cancer often begins with the development of an adenomatous polyp. These polyps often take 10 to 15 years to transform into cancer. Because this development phase is so long, screening and early detection can play a role in the prevention of colorectal cancer, as detection and removal of the polyps can prevent the development of the disease.
For people at average risk of colorectal cancer, the American Cancer Society recommends that routine screening begin at age 50. During a colonoscopy, a flexible tube attached to a camera is inserted through the rectum, allowing physicians to examine the internal lining of the colon and rectum for polyps or other abnormalities. If polyps are identified, they can be removed during the colonoscopy. In general, individuals who have polyps removed are recommended to undergo a follow-up colonoscopy in five years; however, some research indicates that only about one-third of patients adhere to that recommendation.
Researchers from the German Cancer Research Center conducted an observational study to assess the role of both colonoscopy-related factors and polyp characteristics on the risk for colorectal cancer after polyp detection. The population-based, case–control study included nearly 6,500 participants, 3,148 of whom had colorectal cancer. The case and control participants were compared according to polyp characteristics and colonoscopy-related factors, which included incompleteness of procedure, poor bowel preparation, incomplete polyp removal, and lack of follow-up colonoscopy within five years.
The results indicated that patients who had incomplete removal of polyps were four times as likely to develop colorectal cancer and those who did not have a follow-up colonoscopy within five years were nearly three times as likely to develop cancer. The characteristics of polyps appeared to have a smaller influence on risk than the colonoscopy-related factors—for example, the presence of three or more polyps was associated with a moderate risk of developing cancer. The case subjects had higher rates of incomplete polyp removal (29% versus 9.6%), lack of follow-up colonoscopy (26.5% versus 11.5%), and three or more polyps (14.2% versus 7.3%). Overall, 41.1% of cancer cases were statistically attributable to colonoscopy-related factors, compared to 21.7% that were attributable to polyp characteristics.
The researchers concluded that colonoscopy-related factors are more important than polyp characteristics for identifying colorectal cancer risk after colonoscopic polyp detection in the community setting. This underscores the importance of optimizing colonoscopy procedures to ensure complete removal of all polyps as well as proper follow-up.
 Brenner H, Chang-Claude J, Jansen L, et al. Role of colonoscopy and polyp characteristics in colorectal cancer after colonoscopic polyp detection: A population-based case–control study. Annals of Internal Medicine. 2012; 157(4):225-232.
 Cooper GS. Underuse of Colonoscopy for Polyp Surveillance in Medicare Beneficiaries. Presented at the 2012 Digestive Disease Week Annual Meeting; May 19-22, 2012; San Diego. Abstract #Tu1178.