Colorectal Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - Evidence of Benefit
Table 3. Randomized Controlled Screening Trials: Fecal Occult Blood Testing continued...
The primary endpoint was colorectal cancer mortality, with colorectal cancer incidence a key secondary endpoint. All cancers and deaths were ascertained primarily by means of an annual questionnaire. Median follow-up time was 11.9 years and vital status within a year of the cutoff date was known for 99.9% of participants. The incidence rate of colorectal cancer was 11.9 per 10,000 person years in the intervention arm (1,012 cases) versus 15.2 in the usual care arm (1,287 cases) yielding a statistically significant RR of 0.79 (95% CI, 0.72–0.85). The absolute colorectal cancer risk reduction was 0.35%. In the distal colon the RR was 0.71 (95% CI, 0.64–0.80) while in the proximal colon the RR was 0.86 (95% CI, 0.76–0.97). The colorectal cancer mortality rate was 2.9 deaths per 10,000 person-years in the intervention arm (252 deaths) versus 3.9 deaths in the usual care arm (341 deaths) for a statistically significant RR of 0.74 (95% CI, 0.63–0.87). The absolute reduction in risk of colorectal cancer death was 0.11%. The mortality RR for the distal colon was 0.50 (95% CI, 0.38–0.64) while that for the proximal colon was 0.97 (95% CI, 0.77–1.22). Treatment of diagnosed colorectal cancers was very similar by arm within each stage. The rate of bowel perforations was 2.8 per 100,000 sigmoidoscopies. False positive screening results were observed in 20% of men and 13% of women. The RR for deaths from all causes excluding prostate, lung, colorectal, and ovarian cancers was 0.98 (95% CI, 0.96–1.01).
Two case-control studies have been reported that evaluate the efficacy of screening sigmoidoscopy in preventing CRC mortality;[51,52] one study used rigid sigmoidoscopy, and the other used rigid and FS. Both studies were conducted in prepaid health plans and suggested a significantly decreased risk (70%–90%) of fatal cancer of the distal colon or rectum among individuals with a history of one or more sigmoidoscopic examinations compared with nonscreened patients.
There are no strong direct data to determine frequency of screening tests in programs of screening.
Combination of FOBT and Flexible Sigmoidoscopy
A combination of FOBT and sigmoidoscopy might increase the detection of lesions in the left colon (compared with sigmoidoscopy alone) while also increasing the detection of lesions in the right colon. Sigmoidoscopy detects lesions in the left colon directly but detects lesions in the right colon only indirectly when a positive sigmoidoscopy (that may variously be defined as a finding of advanced adenoma, any adenoma, or any polyp) is used to trigger a colonoscopic examination of the whole colon.