Flexible sigmoidoscopy: more than a unilateral breast exam?

Upon reviewing the many wonderful articles and perspective pieces in this Special Issue of Digestive Diseases and Sciences prior to publication, it occurred to me that an important method of screening had not been covered. While in 2010 in the USA \6 % of respondents aged 50–75 reported having screening flexible sigmoidoscopy performed within 5 years (an additional 1.3 % had sigmoidoscopy plus fecal occult blood testing) [1, 2], flexible sigmoidoscopy remains part of the menu of screening options recommended by several professional society guidelines [3–6]. Four recent randomized trials also provide (arguably) the largest body of prospective evidence demonstrating the role of colorectal cancer (CRC) screening in reducing CRC-related mortality of any screening method [7–10]. I therefore decided that it was important to at least provide a brief perspective on flexible sigmoidoscopy as a CRC screening tool, including why it is not used more today in the USA. Four large prospective randomized trials of flexible sigmoidoscopy for CRC screening were published in highimpact journals between 2004 and 2014, having been initiated in the 1990s when flexible sigmoidoscopy was a more common screening tool than in the USA today (Table 1) [7–10]. The trials from the UK (the UK Flexible Sigmoidoscopy Trial), Italy (the Italian Randomized Controlled Trial-SCORE), the USA (the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial-PLCO), and Norway (the Norwegian Colorectal Cancer Prevention Trial-NORCAPP) differ in several ways including how participants were recruited, the number of screening examinations performed, degree of screening outside the trial (‘‘contamination’’), and what findings at sigmoidoscopy generated a subsequent colonoscopy. All, however, demonstrated similar relative and absolute reductions in CRC incidence and cancer-related incidence and mortality. The UK Flexible Sigmoidoscopy Screening Trial is a randomized trial which tested the hypothesis that a single flexible sigmoidoscopy screening examination offered at approximately 60 years of age can lower the incidence and mortality of CRC [7]. CRC incidence and mortality were reduced by 23 and 31 %, respectively, in the intention-totreat analysis (33 and 43 %, respectively, based on perprotocol analysis); incidence of cancer of the rectum and sigmoid was reduced by 36 % in the intention-to-treat analysis and 50 % in the per-protocol analysis. These data have resulted in once in a lifetime flexible sigmoidoscopy being included as an option in the UK National Health Service Bowel Cancer Screening Programme (FOBT is the other option). The Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO) enrolled 154,900 subjects of age 55–74 years in a prospective randomized trial that compared flexible sigmoidoscopy with repeat screening at 3 or 5 years to a usual-care control group [8]. Flexible sigmoidoscopy reduced CRC incidence by 21 % with a benefit observed in both the proximal and distal colon and reduced overall mortality by 26 % (intention-to-treat analyses). Mortality from distal CRC (distal to the splenic flexure) was reduced by 50 %, whereas mortality from proximal CRC was unaffected. The Italian Randomized Controlled Trial (SCORE) demonstrated that once-only sigmoidoscopy significantly reduced CRC incidence by 18 % and insignificantly reduced mortality by 22 % in intention-to-treat analyses; in R. S. Bresalier (&) Department of Gastroenterology, Hepatology and Nutrition, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 1466, Houston, TX 77030, USA e-mail: rbresali@mdanderson.org