Colonoscopy Linked With Lower Risk of Colorectal Cancer Mortality

Nancy N. Baxter, MD, PhD

Colonoscopy is effective for the prevention of colorectal cancer (CRC) deaths, according to the results of a large, population-based, case-control study.

The results also show that individuals who have undergone a colonoscopy have a lower risk of CRC death if the procedure is performed by a gastroenterologist rather than a surgeon or primary care provider. The investigators said the finding bolsters mounting evidence of a link between specialized training in colonoscopy and effectiveness.

Nancy N. Baxter, MD, PhD, staff surgeon at St. Michael’s Hospital in Toronto, Canada, and colleagues elsewhere examined the association of colonoscopy with CRC death in the United States by CRC site and endoscopist specialty.

“Despite a lack of clinical trial data establishing effectiveness, colonoscopy is the most common method of CRC screening in the United States,” the authors wrote.

Using Medicare data from the National Cancer Institute’s SEER cancer registry, the group compared exposure to colonoscopy in 9458 individuals who were diagnosed with colon cancer when they were 70 to 89 years of age and later died of the disease, and 27,641 controls without colon cancer who were matched for sex, year of birth, race, and SEER registry. The SEER program compiles information on cancer incidence and survival from population-based registries representing about 25% of the US population.

Overall, 1073 cases (11.3%) and 6546 controls (23.7%) underwent colonoscopy more than 6 months before being diagnosed with CRC.

Compared with controls, cases were less likely to have undergone colonoscopy (odds ratio [OR], 0.40; 95% CI, 0.37-0.43; P <.001).

Also, the association was stronger for distal CRC (OR, 0.24; 95% CI, 0.21-0.27) than for proximal CRC (OR, 0.58; 95% CI, 0.53-0.64). The researchers said that underlying biological differences in proximal and distal CRC neoplasia may be a reason why colonoscopy is more effective for CRC prevention in the distally located colon. Proximal adenomas are frequently flat and more difficult to identify than pedunculated polyps that “predominate” distally.

They also point out that distal cancers are more likely to develop through the chromosomal instability pathway with the classic slow progression of adenoma to carcinoma than proximal colon cancers, potentially providing greater opportunity for colonoscopic detection.

Colonoscopy performed by a gastroenterologist was significantly more protective for CRC death than colonoscopy done by other providers (OR for colonoscopy performed by gastroenterologists compared with other specialties, 0.71; 95% CI, 0.62-0.81).

Gastroenterologists undergo more comprehensive colonoscopy training during their fellowship training than physicians in other specialties, the authors noted. In addition, colonoscopy “is a complex skill with a long learning curve,” the authors wrote, which means that gastroenterologists may be expected to provide higher quality colonoscopies than other providers.

Baxter NN, Warren JL, Barrett, MJ, et al. Association between colonoscopy and colorectal cancer mortality in a US cohort according to site of cancer and colonoscopist specialty. J Clin Oncol. 2012;30(21):2664-2669.