Colonoscopy was associated with a 61 percent reduction in colorectal cancer mortality among veterans receiving care through the Veterans Affairs (VA) health system. The reduction was observed for both left- and right-sided colorectal cancer, although the association was weaker for right-sided cancer (46 percent versus 72 percent reduction). The findings are published in Annals of Internal Medicine.
Colonoscopy is widely used in the VA health care system, where it is endorsed as a primary colorectal cancer screening option for average-risk patients aged 50 and older. Despite its increased use, it is not known whether colonoscopy decreases colorectal cancer mortality among veterans and whether the effect varies based on the anatomical location of colorectal cancer.
A team of researchers from the VA Medical Centers in Indianapolis and White River Junction (affiliated with Indiana University School of Medicine and Geisel School of Medicine in Dartmouth) reviewed VA-Medicare administrative data, and identified 4,964 case patients who were diagnosed with colorectal cancer between 2002 and 2008 and died of the disease by the end of 2010. Case patients were matched to 4 control patients (n = 19,856) without prior diagnosis of colorectal cancer. Exposure to colonoscopy was determined from 1997 to 6 months before colorectal cancer diagnosis in case patients and to a corresponding date in control patients. Subgroup analysis was performed for patients who had undergone screening colonoscopy.
The researchers found that the patients who died of colorectal cancer were significantly less likely to have undergone any colonoscopy. Colonoscopy was associated with reduced mortality for left-sided cancer and right-sided cancer, although the reduction was smaller for right-sided cancer. The authors suggest that reducing variability in colonoscopy effectiveness, particularly against right-sided colorectal cancer, is critical for effective disease prevention.
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Annals of Internal Medicine (2018). http://annals.org/aim/article/doi/10.7326/M17-0723