Monday, September 23, 2013

Studies show long-term benefits of colorectal cancer screening

Both colonoscopy and fecal occult-blood testing lead to lasting reductions in the risk of death from colorectal cancer, according to a pair of studies in the September 19, 2013, issue of The New England Journal of Medicine. 

One study used data from long-term follow-up studies of health care professionals to analyze the impact of sigmoidoscopy and colonoscopy on colorectal cancer incidence and death. The analysis included a total of 88,902 participants followed up for 22 years. The lead author was Reiko Nishihara, PhD, of Dana-Farber Cancer Institute, Boston. 

On multivariate analysis, hazard ratios (HRs) for colorectal cancer were 0.57 for patients undergoing endoscopy with polypectomy, 0.60 for those with negative sigmoidoscopy, and 0.44 for those with negative colonoscopy. Patients with negative colonoscopy also had a lower incidence of proximal colon cancer, HR 0.73. Colorectal cancer mortality was reduced after both sigmoidoscopy and colonoscopy: HR 0.59 and 0.32, respectively. Only colonoscopy was associated with reduced mortality from proximal colon cancer: HR 0.47. 

The second study evaluated data on 46,551 patients, aged 50 to 80 years, from a randomized trial of annual or biannual fecal occult blood testing versus usual care. The lead author was Dr Aasma Shaukat of Minneapolis Veterans Affairs Health Care System. 

At 30 years' follow-up, the rate of death from colorectal cancer was 1.8% with annual screening, 2.2% with biennial screening, and 2.7% with usual care. Relative risks were 0.68 with annual screening and 0.78 with biennial screening. The mortality benefit of biennial screening was greater in men compared to women; all-cause mortality was not significantly different between groups. 

"[B]oth colonoscopy and fecal occult-blood testing are effective for colorectal-cancer screening, and these new studies support current screening guidelines," according to an accompanying editorial by Drs Theodore R. Levin and Douglas A. Corley. They emphasize that the differing nature of the 2 studies "makes direct comparisons of effectiveness difficult." Forthcoming randomized trials will help in determining which test is better over a 10-year follow-up interval, as well as the overall effectiveness of colorectal cancer screening.

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