R.E. Schoen and Others

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Colorectal-cancer mortality and incidence are reduced with screening by means of fecal occult-blood testing. Endoscopic screening with flexible sigmoidoscopy or colonoscopy is more sensitive than fecal testing for the detection of adenomatous polyps, the precursor lesions of colorectal cancer.

  What were the results of this randomized trial comparing flexible sigmoidoscopy to usual care for screening of colorectal cancer?

In this randomized study, flexible sigmoidoscopy, as compared with usual care, was associated with a 26% reduction in overall colorectal-cancer mortality and a 21% reduction in the incidence of colorectal cancer. Mortality related to distal colorectal cancer was reduced by 50%, and the incidence was reduced by 29%. A significant 14% reduction in the incidence of proximal colorectal cancer was observed, but there was no significant reduction in mortality related to proximal cancer.

  According to the authors, what were the numbers needed to invite for screening via flexible sigmoidoscopy to prevent one diagnosis of colorectal cancer and one colorectal-cancer death?

In this study, the number needed to invite for screening in order to prevent 1 case of colorectal cancer was 282 (95% CI, 210 to 427). The number needed to invite for screening to prevent 1 colorectal-cancer death was 871 (95% CI, 567 to 1874).

A. Participants in the intervention group were offered two screenings with flexible sigmoidoscopy, 3 to 5 years apart. Median follow up was 11.9 years. In the intervention group, 86.6% of participants (67,071) underwent at least one flexible sigmoidoscopic screening, and 50.9% (39,440) underwent two screenings. The estimated rate of endoscopy in the usual-care group during the screening phase was 25.8% (95% CI, 23.6 to 28.0) for flexible sigmoidoscopy, 34.4% (95% CI, 32.0 to 36.8) for colonoscopy, and 46.5% (95% CI, 43.9 to 49.1) for either flexible sigmoidoscopy or colonoscopy.

A. Screening-detected cancers accounted for 24.1% of colorectal cancers (244 of 1012) in the intervention group. Among participants with screening-detected cancers, 82.8% of the cancers were distal, whereas among participants who were never screened, 52.8% were distal, and among participants with cancers not detected by screening, 31.6% were distal (P<0.001). Participants with screening-detected cancers were more likely to have early-stage cancer (stage I or II) than participants who were never screened or those whose tumors were not detected by screening (75.4% vs. 50.9% and 50.7%, respectively; P<0.001).

Table 3. Colorectal-Cancer Incidence and Stage According to Means of Detection.