Colorectal cancers diagnosed within a few years after an index colonoscopy can arise from missed lesions or the development of a new tumor.
Dr Jewel Samadder and colleagues from Utah, USA investigated the proportion, characteristics, and factors that predict interval colorectal cancers that develop within 6–60 months of colonoscopy.
The research team performed a population-based cohort study of Utah residents who underwent colonoscopy examinations from 1995 through 2009 at Intermountain Healthcare or the University of Utah Health System, which provide care to more than 85% of state residents.
Colonoscopy results were linked with cancer histories from the Utah Population Database to identify patients who underwent colonoscopy 6–60 months before a diagnosis of colorectal cancer (interval cancer).
Logistic regression was performed to identify risk factors associated with interval cancers.
|6% of all patients with colorectal cancer had interval cancers|
Of 126,851 patients who underwent colonoscopies, 2659 were diagnosed with colorectal cancer.
The research team found that 6% of these colorectal cancers developed within 6 to 60 months of a colonoscopy.
The team observed that sex and age were not associated with interval colorectal cancers.
A higher percentage of patients with interval colorectal cancer were found to have adenomas at their index colonoscopy, compared with patients found to have colorectal cancer detected at colonoscopy or patients who did not develop cancer.
Interval colorectal cancer tended to be earlier-stage tumors than those detected at index colonoscopy, and to be proximally located.
The researchers found that patients with interval colorectal cancer were more likely to have a family history of colorectal cancer, and had a lower risk of death than patients found to have colorectal cancer at their index colonoscopy.
Dr Samadder and concluded, "In a population-based study in Utah, 6% of all patients with colorectal cancer had interval cancers."
"Interval colorectal cancers were associated with the proximal colon, earlier-stage cancer, lower risk of death, higher rate of adenoma, and family history of colorectal cancer."
"These findings indicate that interval colorectal tumors may arise as the result of distinct biologic features and/or suboptimal management of polyps at colonoscopy."