(HealthDay News) — Six percent of patients with colorectal cancer (CRC) have interval cancers, which develop within six to 60 months of colonoscopy, according to a study published in the April issue of Gastroenterology.
N. Jewel Samadder, MD, from the University of Utah in Salt Lake City, and colleagues examined the proportion, characteristics, and factors that predict interval CRCs in a population-based study of Utah residents. Participants included 126,851 individuals who underwent colonoscopy examinations from 1995 through 2009.
Colonoscopy results were linked with cancer histories to identify patients who underwent colonoscopy 6 to 60 months before CRC diagnosis.
The researchers identified 2,659 diagnoses of CRC, of which 6% developed within 6 to 60 months of colonoscopy. There was no correlation between sex and age and interval CRCs.
Compared with patients found to have CRC detected at colonoscopy or patients who did not develop cancer, a higher percentage of patients with interval CRC had adenomas at their index colonoscopy (57.2% vs 36% and 26%, respectively; P < 0.001).
Compared with tumors detected at index colonoscopy, interval CRCs tended to be earlier stage and proximally located (odds ratio, 2.24; P < 0.001).
Compared with patients found to have CRC at their index colonoscopy, patients with interval CRC were more likely to have family history of CRC (odds ratio, 2.27; P = 0.008) and had a lower risk of death (hazard ratio, 0.63; P < 0.001).
“These findings indicate that interval colorectal tumors may arise as the result of distinct biologic features and/or suboptimal management of polyps at colonoscopy,” the researchers wrote.
Two authors disclosed financial ties to the biotechnology and medical device industries.