The incidence of colorectal cancer overall is reduced for up to 10 years after a negative colonoscopy.
Dr Josh Lakoff and colleagues from Canada determined the incidence of proximal and distal colorectal cancer after a negative complete colonoscopy.
The team identified a cohort of residents aged 50 to 80 years who had a negative complete colonoscopy between 1992 and 1997, by using linked administrative databases.
Cohort members had no prior history of colorectal cancer, inflammatory bowel disease, or recent colonic resection.
|At year 14 the relative rate of distal colorectal cancer was 0.2|
|Clinical Gastroenterology & Hepatology|
Each individual was followed up through 2005, and the relative rate of overall colorectal cancer, distal colorectal cancer, and proximal colorectal cancer was compared with the remaining Ontario population.
The researchers identified a cohort of 110,402 individuals with a negative complete colonoscopy.
The relative rate of colorectal cancer overall and the relative rate of distal colorectal cancer remained significantly lower than the Ontario population.
The team noted that at year 14 the relative rate of distal colorectal cancer was 0.2.
The relative rate of proximal colorectal cancer was significantly lower than the Ontario population in half of the follow-up years, mainly after 7 years of follow-up.
Dr Lakoff’s team concluded, “Over a 14-year follow-up period, negative complete colonoscopy was associated with a subsequent reduced incidence of colorectal cancer overall, and of incident colorectal cancer in the distal colon.”
“However, the reduction in incidence of proximal colorectal cancer differed in magnitude and timing, and occurred in half the follow-up years, mainly after 7 years of follow-up.”
“These results highlight an important limitation of colonoscopy in usual clinical practice.”