Flexible Sigmoidoscopy Reduces CRC Incidence, Mortality

‘One-off’ flexible sigmoidoscopy in middle age protects against colorectal cancer

medwireNews: Flexible sigmoidoscopy, performed only once, offers a significant reduction in colorectal cancer (CRC) incidence and mortality compared with no screening, research suggests.

In the Norwegian Colorectal Cancer Prevention Trial, 20,572 patients aged 50 to 64 years old were randomly assigned to undergo once-only flexible sigmoidoscopy alone or in combination with once-only faecal occult blood testing (FOBT) and 78,220 did not undergo screening.

Patients with a positive screen, defined as the presence of a polyp of 10 mm or greater, an adenoma or CRC, or a positive FOBT were referred for colonoscopy and lesion removal, explain Øyvind Holme, from Sorlandet Hospital in Kristiansand, Norway, and co-authors in JAMA.

Overall, 63% of patients attended screening and after a median of 10.9 years of follow-up, 71 screening group participants had died from CRC compared with 330 controls. This translated to a CRC mortality rate of 31.4 versus 43.1 deaths per 100,000 person–years and with a significant 11.7 absolute rate difference and hazard ratio (HR) of 0.73.

CRC was diagnosed in 253 screening group participants and 1086 controls, giving incidences of 112.6 versus 141.0 cases per 100,000 person–years. Again, there was a significant difference in these rates, of 28.4, and a HR of 0.80.

Of note, the incidence of CRC was significantly reduced by screening for both younger patients, aged 50 to 54 years, and older patients, aged 55 to 64 years, with HRs of 0.68 and 0.83, respectively.

However, there was no significant benefit in terms of CRC outcomes for the addition of FOBT to flexible sigmoidoscopy, the researchers say.

Analysis comparing findings for 10,283 patients in the screening group assigned to flexible sigmoidoscopy alone with the 10,289 patients who also received FOBT found no significant difference in CRC incidence or mortality.

The researchers remark that studies have shown FOBT must be repeated to reduce CRC mortality and note that patients were less likely to adhere to dual-screening than for flexible sigmoidoscopy alone.

Writing in an accompanying editorial, Allan Brett, from University of South Carolina in Columbia, USA, says the Norwegian findings are in line with results from earlier studies conducted in the UK, USA and Italy.

However, he observes that, despite the recommendation for shared decision-making on the best CRC screening test for an individual patient, flexible sigmoidoscopy has been largely superseded by colonoscopy in the USA, where it is the preferred strategy of the American College of Gastroenterology. FOBT is more commonly used in other regions of the world.

Allan Brett adds that the debate over the best screening technique may be rendered moot by recent results for stool DNA testing.

“Repeated at some defined interval, stool DNA testing has potential to reduce colorectal cancer mortality substantially while sharply reducing the number of routine colonoscopies”, he writes.

“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.”


Holme Ø, Løberg M, Kalager M, et al. Effect of flexible sigmoidoscopy screening on colorectal cancer incidence and mortality. A randomized clinical trial. JAMA 2014; 312(6): 606–615.  doi:10.1001/jama.2014.8266

Brett A. Flexible sigmoidoscopy for colorectal cancer screening. More evidence, persistent ironies. JAMA 2014; 312 (6): 601–602.  doi:10.1001/jama.2014.8613

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