Flexible Sigmoidoscopy Reduces Colorectal Cancer Incidence and Mortality Compared to Usual Care

DynaMed Weekly Update - Volume 7, Issue 22

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To screen patients at average risk for colorectal cancer, the United States Preventive Services Task Force (USPSTF) recommends 1 of 3 screening options: high-sensitivity fecal occult blood testing every year, flexible sigmoidoscopy every 5 years or colonoscopy every 10 years for patients aged 50-70 years (Ann Intern Med 2008 Nov 4;149(9):627).The American Cancer Society and American Gastroenterological Association recommendations include the same 3 options, but also include double-contrast barium enema every 5 years or computed tomographic (CT) colonography every 5 years as additional options (CA Cancer J Clin 2008 May-Jun;58(3):130). The optimal method of screening has yet to be determined. The efficacy of flexible sigmoidoscopy was evaluated in 154,900 patients as part of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.

Patients aged 55-74 years were recruited through mass mailings and randomized to screening with flexible sigmoidoscopy vs. usual care from 1993-2001. The sigmoidoscopy group was offered screening at baseline and again 5 years later (3 years later for patients recruited during the first 2 years of the trial). Patients with a positive screen (detection of polyp or mass) were referred for additional diagnostic consultation. In the sigmoidoscopy group, 83.5% had baseline screening and 54% had repeat screening. Colonoscopy was performed in 5.5% during their first 5 years in the trial (screening phase) and in 47.7% after the screening phase. Details of screening that the usual care group received were not given, but 46.5% had either flexible sigmoidoscopy or colonoscopy during the screening phase of the trial and 48% had routine colonoscopy after the screening phase.

Median follow-up was 11.9 years. Colorectal cancer occurred in 1.31% in the flexible sigmoidoscopy group vs. 1.66% in the usual care group (p < 0.001, NNT 286), and colorectal cancer mortality was significantly reduced with sigmoidoscopy (0.325% vs. 0.44%, p < 0.001, NNT 870) (level 1 [likely reliable] evidence). Incidence per 10,000 person-years was 5.6 vs. 7.9 for distal colorectal cancer (p < 0.95) and 6 vs. 7 for proximal colorectal cancer. There was no significant difference in death from other causes, excluding prostate, lung and ovarian cancers (11.8% vs. 12%) (N Engl J Med 2012 May 21 early online).

For more information, see the Colorectal cancer screening topic in DynaMed.