Colonoscopy is advocated for screening and prevention of colorectal cancer, but randomized trials supporting the benefit of this practice are not available.
Dr Nancy Baxter and colleagues from Canada evaluated the association between colonoscopy and colorectal cancer deaths.
The team conducted a population-based, case–control study of persons age 52 to 90 years who received a colorectal cancer diagnosis from 1996 to 2001 and died of colorectal cancer by 2003.
The research team randomly selected 5 controls matched by age, sex, geographic location, and socioeconomic status for each case patient.
|Complete colonoscopy was associated with fewer deaths from left-sided colorectal cancer only|
|Annals of Internal Medicine|
Administrative claims data were used to detect exposure to any colonoscopy and complete colonoscopy from 1992 to an index date 6 months before diagnosis in each case patient and the same assigned date in matched controls.
Exposures in case patients and controls were compared by using conditional logistic regression to control for comorbid conditions.
Secondary analyses were done to see whether associations differed by site of primary colorectal cancer, age, or sex.
The team identified 10,292 case patients and 51,460 controls.
The research team found that 719 case patients, and 5031 controls had undergone colonoscopy.
Compared with controls, case patients were less likely to have undergone any attempted colonoscopy or complete colonoscopy.
Complete colonoscopy was strongly associated with fewer deaths from left-sided colorectal cancer but not from right-sided colorectal cancer.
Screening could not be differentiated from diagnostic procedures.
Dr Baxter’s team comments, “In usual practice, colonoscopy is associated with fewer deaths from colorectal cancer.”
“This association is primarily limited to deaths from cancer developing in the left side of the colon.”