Screening with flexible sigmoidoscopy resulted in a reduced incidence and rate of death of colorectal cancer, compared with no screening, according to a new study with 100,000 participants.

Colorectal cancer is the third most commonly occurring cancer worldwide. Most colorectal cancer cases develop from adenomas, or benign tumors. Removal of adenomas by colonoscopy or flexible sigmoidoscopy, a thin flexible lighted tube used to inspect the inside of the rectum and lower part of the colon, has been endorsed as a primary prevention tool for colorectal cancer.

Øyvind Holme, MD, of the Sorlandet Hospital Kristiansand, in Norway, and colleagues randomly assigned study participants in Norway to receive once-only flexible sigmoidoscopy (n=10, 283); a combination of once-only flexible sigmoidoscopy and fecal occult blood testing (FOBT; n=10,289), or no intervention (control group; n=78,220). Screening was performed in 1999 to 2000 (age group: 55-64 years) and in 2001 (age group: 50-54 years), with follow-up ending December 2011. Participants with positive screening test results were offered colonoscopy. The article was published in JAMA (2014; doi:10.1001/jama.2014.8266).

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After a median of 11 years, 71 participants died of colorectal cancer in the screening groups vs 330 in the control group. Colorectal cancer was diagnosed in 253 participants in the screening groups vs 1,086 in the control group. Analysis of the data indicated that compared with no screening, flexible sigmoidoscopy screening reduced colorectal cancer incidence by 20% (absolute difference, 28.4 cases/100,000 person years) and colorectal cancer mortality by 27% (absolute difference, 11.7 deaths/100,000 person years). These outcomes had no significant difference between the flexible sigmoidoscopy only vs the flexible sigmoidoscopy and FOBT screening groups.

Younger participants (50 to 54 years) seemed to benefit at least as much from the screening interventions as older participants (55 to 64 years).

In an accompanying editorial (JAMA; 2014; doi:10.1001/jama.2014.8613), Allan S. Brett, MD, of the University of South Carolina School of Medicine in Columbia, wrote that although there may be debate over the use of flexible sigmoidoscopy or colonoscopy for colorectal cancer screening, another screening technique, stool DNA testing, might render the debate moot in the not-too­distant future.

“A large, recently published study examined the performance of a multitarget stool test that identifies several DNA abnormalities associated with colorectal cancer or precancerous adenomas. With colonoscopy as the reference standard, the sensitivity of the stool DNA test was 92% for detecting cancer and 42% for detecting advanced precancerous lesions; specificity was 90%. Notably, the stool DNA test was much more sensitive than a separate fecal immunochemical test for hemoglobin performed for each participant,” said Brett.

“Repeated at some defined interval, stool DNA testing has potential to reduce colorectal cancer mortality substantially while sharply reducing the number of routine colonoscopies. For now, however, the muddled landscape of colorectal cancer screening in the United States continues, and the place of flexible sigmoidoscopy among screening tools remains unsettled,” explained Brett.