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W2016688863 abstract "The ultimate goal of colorectal cancer screening is to reduce the burden of disease, as measured by colorectal cancer incidence and/or cancer-related mortality.The seminal National Polyp Study (NPS) suggested that colonoscopy with polypectomy can lead to as much as a 90% reduction in the subsequent risk of developing colorectal cancer (CRC).1Winawer S.J. Zauber A.G. Ho M.N. et al.Prevention of colorectal cancer by colonoscopic polypectomy.The National Polyp Study Workgroup. N Engl J Med. 1993; 329: 1977-1981Crossref PubMed Scopus (3862) Google Scholar Many subsequent studies have found a lower magnitude of protection.2Robertson D.J. Greenberg E.R. Beach M. et al.Colorectal cancer in patients under close colonoscopic surveillance.Gastroenterology. 2005; 129: 34-41Abstract Full Text Full Text PDF PubMed Scopus (388) Google Scholar, 3Muller A.D. Sonnenberg A. Prevention of colorectal cancer by flexible endoscopy and polypectomy. A case-control study of 32,702 veterans.Ann Intern Med. 1995; 123: 904-910Crossref PubMed Scopus (561) Google Scholar, 4Schoen R.E. Surveillance after positive and negative colonoscopy examinations: issues, yields, and use.Am J Gastroenterol. 2003; 98: 1237-1246Crossref PubMed Scopus (46) Google Scholar, 5Loeve F. van Ballegooijen M. Snel P. et al.Colorectal cancer risk after colonoscopic polypectomy: a population-based study and literature search.Eur J Cancer. 2005; 41: 416-422Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar It is likely that some of the difference is owing to the missed detection of adenomas and cancers at the initial examination. The initial colonoscopies in the NPS were careful examinations performed by a select group of expert endoscopists; a number of colonoscopies were repeated within 3 months of the initial examination when there was doubt about the adequacy of clearance of the colon at the initial examination. Conversely, colonoscopies in the later studies were performed in real-world practice settings by many different endoscopists with varying levels of training and competency.Indeed, some studies estimate that approximately 5% of CRCs may be missed at the initial examination.6Bressler B. Paszat L.F. Chen Z. et al.Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis.Gastroenterology. 2007; 132: 96-102Abstract Full Text Full Text PDF PubMed Scopus (518) Google Scholar, 7Leaper M. Johnston M.J. Barclay M. et al.Reasons for failure to diagnose colorectal carcinoma at colonoscopy.Endoscopy. 2004; 36: 499-503Crossref PubMed Scopus (129) Google Scholar There are inherent limitations of the optical colonoscopy, with a higher chance of missing lesions behind colonic folds, as suggested by computed tomography colonography.8Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google Scholar However, more intriguing and concerning is the occurrence of a wide variation in the performance and outcomes of colonoscopy among different endoscopists and different settings.9Rex D.K. Maximizing detection of adenomas and cancers during colonoscopy.Am J Gastroenterol. 2006; 101: 2866-2877Crossref PubMed Scopus (237) Google Scholar In Ontario, Canada, the rates of completion of colonoscopy to the cecum are lower if the colonoscopy is performed by family physicians or general internists or if it is performed in ambulatory care centers.10Shah H.A. Paszat L.F. Saskin R. et al.Factors associated with incomplete colonoscopy: a population-based study.Gastroenterology. 2007; 132: 2297-2303Abstract Full Text Full Text PDF PubMed Scopus (291) Google Scholar Endoscopists who perform fewer than 100 colonoscopies each year are less likely to complete the examination to the cecum.11Wexner S.D. Garbus J.E. Singh J.J. A prospective analysis of 13,580 colonoscopies. Reevaluation of credentialing guidelines.Surg Endosc. 2001; 15: 251-261Crossref PubMed Scopus (218) Google Scholar In some series, the missed cancer rate is higher for colonoscopies performed by primary care physicians or in an office or in rural setting.6Bressler B. Paszat L.F. Chen Z. et al.Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis.Gastroenterology. 2007; 132: 96-102Abstract Full Text Full Text PDF PubMed Scopus (518) Google Scholar, 12Singh H. Turner D. Xue L. et al.Colorectal Cancers after a negative colonoscopy.Gastroenterology. 2007; 132 ([abstract]): A-149Google Scholar Even among gastroenterologists, there may be a difference in the sensitivity of colonoscopy for CRC detection.13Rex D.K. Rahmani E.Y. Haseman J.H. et al.Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer in clinical practice.Gastroenterology. 1997; 112: 17-23Abstract Full Text PDF PubMed Scopus (515) Google Scholar Furthermore, recent studies suggest that there is a higher risk of associated complications if endoscopy is performed by low-volume endoscopists.14Rabeneck L. Paszat L.F. Hilsden R.J. et al.Bleeding and perforation after outpatient colonoscopy and their risk factors in usual clinical practice.Gastroenterology. 2008; 135: 1899-1906Abstract Full Text Full Text PDF PubMed Scopus (366) Google Scholar, 15Singh H. Penfold R.B. De Coster C. et al.Colonoscopy and its complications across a Canadian regional health authority.Gastrointest Endosc. 2009; 69: 665-671Abstract Full Text Full Text PDF PubMed Scopus (94) Google ScholarThe ultimate goal of CRC screening is to reduce the burden of disease, as measured by CRC incidence and/or cancer-related mortality. However, because a very large sample size of colonoscopies performed by each endoscopist would be required to demonstrate the potential variation in the detection of CRC, studies evaluating differences in lesion detection rates among individual endoscopists have usually focused on polyp or adenoma detection rates. The individual endoscopist can be a more important predictor of detecting adenomas of any size than even the age and sex of the individuals undergoing the procedures.16Chen S.C. Rex D.K. Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy.Am J Gastroenterol. 2007; 102: 856-861Crossref PubMed Scopus (334) Google ScholarOver the past few years, several investigators have tried to determine the reasons for the differences in detection rates of colorectal lesions among different endoscopists. Withdrawal time during colonoscopy is a relatively easily measurable variable and has therefore become a focus. In this issue of GIE, Imperiale et al17Imperiale T.F. Glowinski E.A. Juliar B.E. et al.Variation in polyp detection rates at screening colonoscopy.Gastrointest Endosc. 2009; 69: 1288-1295Abstract Full Text Full Text PDF PubMed Scopus (116) Google Scholar report on the analysis of the correlation of procedure time and polyp detection rates from the Eli Lily's CRC screening program in Indiana. They excluded endoscopists with the lowest volume of colonoscopies in the program (40 endoscopists who performed colonoscopies on 261 patients) and assessed the mean polyp detection rate as a function of the mean total procedure time and estimated withdrawal time. The overall polyp (and adenoma) detection rate was dependent on the procedure time; the detection rate for larger advanced neoplastic lesions did not reach statistical significance (P = .07). They did not analyze the results separately for intermediate-size (6-10 mm) polyps. Of note, the study has a serious limitation in that only aggregate data per endoscopist were analyzed and individual patient-level colonoscopy data were not reported. Thus, patient and procedure characteristics cannot be adequately analyzed. In addition, the regression analyses presented may not accurately estimate the statistical significance or fractions of variance explained by procedure time because the inherent variations in individual patient characteristics and outcomes are not taken into account. Another limitation is that the primary variable of interest, the withdrawal time, was not measured directly, but was extrapolated from the total procedure time by subtracting 8 minutes, which was arbitrarily assumed to be the insertion time for each colonoscopy. It is possible that some endoscopists may have a faster insertion time but then take longer to withdraw the colonoscope compared with others who may have the same overall total procedure time but spend a larger proportion of time on insertion. The authors did not adjust the P values for multiple comparisons, which would also tend to exaggerate statistical significance. Conversely, although their findings should be considered exploratory in nature, the data are based on a large number of colonoscopies.In contrast to the current study, Barclay et al,18Barclay R.L. Vicari J.J. Doughty A.S. et al.Colonoscopic withdrawal times and adenoma detection during screening colonoscopy.N Engl J Med. 2006; 355: 2533-2541Crossref PubMed Scopus (1074) Google Scholar using individual patient data, found a significant association between variation in the advanced neoplasia detection rate and withdrawal time. Moreover, Barclay et al,19Barclay R.L. Vicari J.J. Greenlaw R.L. Effect of a time-dependent colonoscopic withdrawal protocol on adenoma detection during screening colonoscopy.Clin Gastroenterol Hepatol. 2008; 6: 1091-1098Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar in a follow-up study, demonstrated an increased detection rate of advanced neoplasia by implementing a protocol of a minimum of 8 minutes for colonoscope withdrawal. In another recent study, there was a significant association of polyp detection rate with withdrawal time for polyps smaller than 5 mm.20Simmons D.T. Harewood G.C. Baron T.H. et al.Impact of endoscopist withdrawal speed on polyp yield: implications for optimal colonoscopy withdrawal time.Aliment Pharmacol Ther. 2006; 24: 965-971Crossref PubMed Scopus (198) Google Scholar However, when the baseline polyp detection rate is high, implementing a policy of a minimum of 7 minutes for colonoscope withdrawal in an academic medical center may not lead to improved polyp detection rates.21Sawhney M.S. Cury M.S. Neeman N. et al.Effect of institution-wide policy of colonoscopy withdrawal time > or = 7 minutes on polyp detection.Gastroenterology. 2008; 135: 1892-1898Abstract Full Text Full Text PDF PubMed Scopus (145) Google ScholarThe value of removing small adenomas, the detection rate of which varies the most among endoscopists, needs to be better defined. However, the current recommendations are to remove all adenomatous polyps found at colonoscopy.22Lieberman D. Nadel M. Smith R.A. et al.Standardized colonoscopy reporting and data system: report of the Quality Assurance Task Group of the National Colorectal Cancer Roundtable.Gastrointest Endosc. 2007; 65: 757-766Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar Although most small polyps are benign and will take years to grow, many individuals will not return for repeat colonoscopy. Moreover, the results of NPS and the modeling studies are based on removal of all detected adenomas at baseline.Adequate withdrawal time is only one of the characteristics of complete colonic examination. Colonoscopy completion to the cecum, adequate bowel preparation (features that were not commented on in the current study description), and adequate visualization of colonic mucosa are well-recognized important additional features. Adequate colonic distention and removal of residual fluid allow better visualization of colonic mucosa, improving the adenoma detection rates.23Rex D.K. Colonoscopic withdrawal technique is associated with adenoma miss rates.Gastrointest Endosc. 2000; 51: 33-36Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar However, there are no large studies evaluating the variation in different aspects of withdrawal technique and mucosal examination among different endoscopists. The Quality Assurance Task Group of the National Colorectal Cancer Roundtable recently developed a standardized colonoscopy reporting system to document variation in performance of colonoscopy and to develop benchmarks for the various indicators.22Lieberman D. Nadel M. Smith R.A. et al.Standardized colonoscopy reporting and data system: report of the Quality Assurance Task Group of the National Colorectal Cancer Roundtable.Gastrointest Endosc. 2007; 65: 757-766Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar This system will likely evolve; for example, one recommendation is to obtain cecal photographs to document the cecal intubation, even though video recording provides much more convincing evidence for the uninvolved reviewers.24Rex D.K. Still photography versus videotaping for documentation of cecal intubation: a prospective study.Gastrointest Endosc. 2000; 51: 451-459Abstract Full Text Full Text PDF PubMed Scopus (66) Google ScholarThe perceived adequacy of the endoscopic examination not only affects the subsequent risk of developing CRC, but also the recommendation for the screening intervals. In the United States, the Multisociety Task Force recommends flexible sigmoidoscopy at 5-year intervals because of the concern about the adequacy of the examination in the usual clinical practice, even though there is evidence to suggest that longer intervals may be adequate.25Winawer S. Fletcher R. Rex D. et al.Colorectal cancer screening and surveillance: clinical guidelines and rationale-Update based on new evidence.Gastroenterology. 2003; 124: 544-560Abstract Full Text PDF PubMed Scopus (1972) Google Scholar Two case-control studies suggest that the protective effect of sigmoidoscopy persists for at least 10 years.26Selby J.V. Friedman G.D. Quesenberry Jr., C.P. et al.A case-control study of screening sigmoidoscopy and mortality from colorectal cancer.N Engl J Med. 1992; 326: 653-657Crossref PubMed Scopus (1564) Google Scholar, 27Newcomb P.A. Storer B.E. Morimoto L.M. et al.Long-term efficacy of sigmoidoscopy in the reduction of colorectal cancer incidence.J Natl Cancer Inst. 2003; 95: 622-625Crossref PubMed Scopus (175) Google Scholar Flexible sigmoidoscopies are performed at 10-year intervals in the Colon Cancer Prevention Program of Kaiser Permanente. The Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial in the United States is evaluating flexible sigmoidoscopy every 5 years. In contrast, in Europe, once-in-a-lifetime flexible sigmoidoscopy is being evaluated in 2 clinical trials.28Benson V.S. Patnick J. Davies A.K. et al.Colorectal cancer screening: a comparison of 35 initiatives in 17 countries.Int J Cancer. 2008; 122: 1357-1367Crossref PubMed Scopus (220) Google ScholarThere is evidence to suggest that benefits of colonoscopy may last longer than 10 years.29Singh H. Turner D. Xue L. et al.Risk of developing colorectal cancer following a negative colonoscopy examination: evidence for a 10-year interval between colonoscopies.JAMA. 2006; 295: 2366-2373Crossref PubMed Scopus (362) Google Scholar, 30Brenner H. Chang-Claude J. Seiler C.M. et al.Does a negative screening colonoscopy ever need to be repeated?.Gut. 2006; 55: 1145-1150Crossref PubMed Scopus (159) Google Scholar Modeling with data from the NPS suggests that the initial colonoscopy is the most important examination.31Zauber A. Winawer S.J. Lansdorp-Vogelaar I. et al.Effect of initial polypectomy versus surveillance polypectomy on colorectal cancer mortality reduction: micro-simulation modeling of the National Polyp Study.Am J Gastroenterol. 2007; 102: S558Crossref PubMed Scopus (101) Google Scholar Another recent modeling study, based on autopsy data, predicts that approximately 80% of individuals presenting with CRC between the ages of 50 and 80 already have an adenoma in their colon at age 50. In this model, the majority of CRCs can be prevented by a single colonoscopy at age 50, followed by surveillance of those with adenomas.32Geul K. Habbema J.D.F. Ting C.W. et al.Prevention of colorectal cancer by early colonoscopy: a feasible perspective, deduced from autopsy data.Gastroenterology. 2007; 132 ([abstract]): A313Google Scholar For those at average risk of developing CRC and if the initial colonoscopy is negative for colorectal neoplasia, it may be time to consider the strategy of once-in-a-lifetime colonoscopy. Currently, the United States, Germany, and Poland are among the very few countries pursuing widespread screening colonoscopy outside research protocols.28Benson V.S. Patnick J. Davies A.K. et al.Colorectal cancer screening: a comparison of 35 initiatives in 17 countries.Int J Cancer. 2008; 122: 1357-1367Crossref PubMed Scopus (220) Google Scholar Once-in-a-lifetime colonoscopy (if negative) will likely make screening colonoscopy feasible for most other countries and may provide the greatest benefit, even in countries currently pursuing screening colonoscopy because resources could then be directed toward the initial screening instead of surveillance of individuals with a low risk of CRC (and hence increase screening rates, even without additional resources). However, such strategies can only be considered if the inequities in the performance of the colonoscopies can be reduced, resulting in more uniform outcomes after the procedure. In fact, at least 2 recent population-based studies have highlighted the fact that colonoscopic screening as practiced in the community does not always provide adequate protection against CRC detection or mortality, especially for right-sided tumors.33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar, 34Baxter N.N. Goldwasser M.A. Paszat M.F. et al.Association of colonoscopy and death from colorectal cancer: a population-based case-control study.Ann Intern Med. 2009; 150: 1-8Crossref PubMed Scopus (1048) Google Scholar Singh et al,33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar in a large case-control study of colonoscopies in the California Medicaid population, found that the relative risk of CRC after a negative colonoscopy (compared with no screening) was 0.55 (95% CI, 0.16-0.65), but there were large differences between left- and right-sided lesions. The relative risk for left-sided tumors after a negative colonoscopy was 0.16 (95% CI, 0.09-0.28), whereas that for right-sided lesions was a far more modest 0.67 (95% CI, 0.51-0.88).33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar The beneficial effects of sigmoidoscopy were considerably smaller.33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar Baxter et al34Baxter N.N. Goldwasser M.A. Paszat M.F. et al.Association of colonoscopy and death from colorectal cancer: a population-based case-control study.Ann Intern Med. 2009; 150: 1-8Crossref PubMed Scopus (1048) Google Scholar studied the practice of colonoscopy in Ontario, Canada, in another case-control study and concluded that the beneficial effect of screening colonoscopy on mortality from CRC was confined to the left-sided tumors only.Colonoscopic CRC screening cannot eliminate all subsequent risk of developing CRC, but we can certainly improve the current effectiveness in the routine clinical practice by improving the quality of the examinations. Whether the optimal withdrawal time to allow complete visualization of colonic mucosa for an average endoscopist should be 6 or 10 minutes or another time interval still needs to be better defined. Optimal withdrawal is essential to ensure complete colonic examination. Spending 6 or 10 minutes during withdrawal is a small price to pay for improving outcomes after colonoscopy. The ultimate goal of colorectal cancer screening is to reduce the burden of disease, as measured by colorectal cancer incidence and/or cancer-related mortality.The seminal National Polyp Study (NPS) suggested that colonoscopy with polypectomy can lead to as much as a 90% reduction in the subsequent risk of developing colorectal cancer (CRC).1Winawer S.J. Zauber A.G. Ho M.N. et al.Prevention of colorectal cancer by colonoscopic polypectomy.The National Polyp Study Workgroup. N Engl J Med. 1993; 329: 1977-1981Crossref PubMed Scopus (3862) Google Scholar Many subsequent studies have found a lower magnitude of protection.2Robertson D.J. Greenberg E.R. Beach M. et al.Colorectal cancer in patients under close colonoscopic surveillance.Gastroenterology. 2005; 129: 34-41Abstract Full Text Full Text PDF PubMed Scopus (388) Google Scholar, 3Muller A.D. Sonnenberg A. Prevention of colorectal cancer by flexible endoscopy and polypectomy. A case-control study of 32,702 veterans.Ann Intern Med. 1995; 123: 904-910Crossref PubMed Scopus (561) Google Scholar, 4Schoen R.E. Surveillance after positive and negative colonoscopy examinations: issues, yields, and use.Am J Gastroenterol. 2003; 98: 1237-1246Crossref PubMed Scopus (46) Google Scholar, 5Loeve F. van Ballegooijen M. Snel P. et al.Colorectal cancer risk after colonoscopic polypectomy: a population-based study and literature search.Eur J Cancer. 2005; 41: 416-422Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar It is likely that some of the difference is owing to the missed detection of adenomas and cancers at the initial examination. The initial colonoscopies in the NPS were careful examinations performed by a select group of expert endoscopists; a number of colonoscopies were repeated within 3 months of the initial examination when there was doubt about the adequacy of clearance of the colon at the initial examination. Conversely, colonoscopies in the later studies were performed in real-world practice settings by many different endoscopists with varying levels of training and competency. The ultimate goal of colorectal cancer screening is to reduce the burden of disease, as measured by colorectal cancer incidence and/or cancer-related mortality. The ultimate goal of colorectal cancer screening is to reduce the burden of disease, as measured by colorectal cancer incidence and/or cancer-related mortality. Indeed, some studies estimate that approximately 5% of CRCs may be missed at the initial examination.6Bressler B. Paszat L.F. Chen Z. et al.Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis.Gastroenterology. 2007; 132: 96-102Abstract Full Text Full Text PDF PubMed Scopus (518) Google Scholar, 7Leaper M. Johnston M.J. Barclay M. et al.Reasons for failure to diagnose colorectal carcinoma at colonoscopy.Endoscopy. 2004; 36: 499-503Crossref PubMed Scopus (129) Google Scholar There are inherent limitations of the optical colonoscopy, with a higher chance of missing lesions behind colonic folds, as suggested by computed tomography colonography.8Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google Scholar However, more intriguing and concerning is the occurrence of a wide variation in the performance and outcomes of colonoscopy among different endoscopists and different settings.9Rex D.K. Maximizing detection of adenomas and cancers during colonoscopy.Am J Gastroenterol. 2006; 101: 2866-2877Crossref PubMed Scopus (237) Google Scholar In Ontario, Canada, the rates of completion of colonoscopy to the cecum are lower if the colonoscopy is performed by family physicians or general internists or if it is performed in ambulatory care centers.10Shah H.A. Paszat L.F. Saskin R. et al.Factors associated with incomplete colonoscopy: a population-based study.Gastroenterology. 2007; 132: 2297-2303Abstract Full Text Full Text PDF PubMed Scopus (291) Google Scholar Endoscopists who perform fewer than 100 colonoscopies each year are less likely to complete the examination to the cecum.11Wexner S.D. Garbus J.E. Singh J.J. A prospective analysis of 13,580 colonoscopies. Reevaluation of credentialing guidelines.Surg Endosc. 2001; 15: 251-261Crossref PubMed Scopus (218) Google Scholar In some series, the missed cancer rate is higher for colonoscopies performed by primary care physicians or in an office or in rural setting.6Bressler B. Paszat L.F. Chen Z. et al.Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis.Gastroenterology. 2007; 132: 96-102Abstract Full Text Full Text PDF PubMed Scopus (518) Google Scholar, 12Singh H. Turner D. Xue L. et al.Colorectal Cancers after a negative colonoscopy.Gastroenterology. 2007; 132 ([abstract]): A-149Google Scholar Even among gastroenterologists, there may be a difference in the sensitivity of colonoscopy for CRC detection.13Rex D.K. Rahmani E.Y. Haseman J.H. et al.Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer in clinical practice.Gastroenterology. 1997; 112: 17-23Abstract Full Text PDF PubMed Scopus (515) Google Scholar Furthermore, recent studies suggest that there is a higher risk of associated complications if endoscopy is performed by low-volume endoscopists.14Rabeneck L. Paszat L.F. Hilsden R.J. et al.Bleeding and perforation after outpatient colonoscopy and their risk factors in usual clinical practice.Gastroenterology. 2008; 135: 1899-1906Abstract Full Text Full Text PDF PubMed Scopus (366) Google Scholar, 15Singh H. Penfold R.B. De Coster C. et al.Colonoscopy and its complications across a Canadian regional health authority.Gastrointest Endosc. 2009; 69: 665-671Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar The ultimate goal of CRC screening is to reduce the burden of disease, as measured by CRC incidence and/or cancer-related mortality. However, because a very large sample size of colonoscopies performed by each endoscopist would be required to demonstrate the potential variation in the detection of CRC, studies evaluating differences in lesion detection rates among individual endoscopists have usually focused on polyp or adenoma detection rates. The individual endoscopist can be a more important predictor of detecting adenomas of any size than even the age and sex of the individuals undergoing the procedures.16Chen S.C. Rex D.K. Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy.Am J Gastroenterol. 2007; 102: 856-861Crossref PubMed Scopus (334) Google Scholar Over the past few years, several investigators have tried to determine the reasons for the differences in detection rates of colorectal lesions among different endoscopists. Withdrawal time during colonoscopy is a relatively easily measurable variable and has therefore become a focus. In this issue of GIE, Imperiale et al17Imperiale T.F. Glowinski E.A. Juliar B.E. et al.Variation in polyp detection rates at screening colonoscopy.Gastrointest Endosc. 2009; 69: 1288-1295Abstract Full Text Full Text PDF PubMed Scopus (116) Google Scholar report on the analysis of the correlation of procedure time and polyp detection rates from the Eli Lily's CRC screening program in Indiana. They excluded endoscopists with the lowest volume of colonoscopies in the program (40 endoscopists who performed colonoscopies on 261 patients) and assessed the mean polyp detection rate as a function of the mean total procedure time and estimated withdrawal time. The overall polyp (and adenoma) detection rate was dependent on the procedure time; the detection rate for larger advanced neoplastic lesions did not reach statistical significance (P = .07). They did not analyze the results separately for intermediate-size (6-10 mm) polyps. Of note, the study has a serious limitation in that only aggregate data per endoscopist were analyzed and individual patient-level colonoscopy data were not reported. Thus, patient and procedure characteristics cannot be adequately analyzed. In addition, the regression analyses presented may not accurately estimate the statistical significance or fractions of variance explained by procedure time because the inherent variations in individual patient characteristics and outcomes are not taken into account. Another limitation is that the primary variable of interest, the withdrawal time, was not measured directly, but was extrapolated from the total procedure time by subtracting 8 minutes, which was arbitrarily assumed to be the insertion time for each colonoscopy. It is possible that some endoscopists may have a faster insertion time but then take longer to withdraw the colonoscope compared with others who may have the same overall total procedure time but spend a larger proportion of time on insertion. The authors did not adjust the P values for multiple comparisons, which would also tend to exaggerate statistical significance. Conversely, although their findings should be considered exploratory in nature, the data are based on a large number of colonoscopies. In contrast to the current study, Barclay et al,18Barclay R.L. Vicari J.J. Doughty A.S. et al.Colonoscopic withdrawal times and adenoma detection during screening colonoscopy.N Engl J Med. 2006; 355: 2533-2541Crossref PubMed Scopus (1074) Google Scholar using individual patient data, found a significant association between variation in the advanced neoplasia detection rate and withdrawal time. Moreover, Barclay et al,19Barclay R.L. Vicari J.J. Greenlaw R.L. Effect of a time-dependent colonoscopic withdrawal protocol on adenoma detection during screening colonoscopy.Clin Gastroenterol Hepatol. 2008; 6: 1091-1098Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar in a follow-up study, demonstrated an increased detection rate of advanced neoplasia by implementing a protocol of a minimum of 8 minutes for colonoscope withdrawal. In another recent study, there was a significant association of polyp detection rate with withdrawal time for polyps smaller than 5 mm.20Simmons D.T. Harewood G.C. Baron T.H. et al.Impact of endoscopist withdrawal speed on polyp yield: implications for optimal colonoscopy withdrawal time.Aliment Pharmacol Ther. 2006; 24: 965-971Crossref PubMed Scopus (198) Google Scholar However, when the baseline polyp detection rate is high, implementing a policy of a minimum of 7 minutes for colonoscope withdrawal in an academic medical center may not lead to improved polyp detection rates.21Sawhney M.S. Cury M.S. Neeman N. et al.Effect of institution-wide policy of colonoscopy withdrawal time > or = 7 minutes on polyp detection.Gastroenterology. 2008; 135: 1892-1898Abstract Full Text Full Text PDF PubMed Scopus (145) Google Scholar The value of removing small adenomas, the detection rate of which varies the most among endoscopists, needs to be better defined. However, the current recommendations are to remove all adenomatous polyps found at colonoscopy.22Lieberman D. Nadel M. Smith R.A. et al.Standardized colonoscopy reporting and data system: report of the Quality Assurance Task Group of the National Colorectal Cancer Roundtable.Gastrointest Endosc. 2007; 65: 757-766Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar Although most small polyps are benign and will take years to grow, many individuals will not return for repeat colonoscopy. Moreover, the results of NPS and the modeling studies are based on removal of all detected adenomas at baseline. Adequate withdrawal time is only one of the characteristics of complete colonic examination. Colonoscopy completion to the cecum, adequate bowel preparation (features that were not commented on in the current study description), and adequate visualization of colonic mucosa are well-recognized important additional features. Adequate colonic distention and removal of residual fluid allow better visualization of colonic mucosa, improving the adenoma detection rates.23Rex D.K. Colonoscopic withdrawal technique is associated with adenoma miss rates.Gastrointest Endosc. 2000; 51: 33-36Abstract Full Text Full Text PDF PubMed Scopus (333) Google Scholar However, there are no large studies evaluating the variation in different aspects of withdrawal technique and mucosal examination among different endoscopists. The Quality Assurance Task Group of the National Colorectal Cancer Roundtable recently developed a standardized colonoscopy reporting system to document variation in performance of colonoscopy and to develop benchmarks for the various indicators.22Lieberman D. Nadel M. Smith R.A. et al.Standardized colonoscopy reporting and data system: report of the Quality Assurance Task Group of the National Colorectal Cancer Roundtable.Gastrointest Endosc. 2007; 65: 757-766Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar This system will likely evolve; for example, one recommendation is to obtain cecal photographs to document the cecal intubation, even though video recording provides much more convincing evidence for the uninvolved reviewers.24Rex D.K. Still photography versus videotaping for documentation of cecal intubation: a prospective study.Gastrointest Endosc. 2000; 51: 451-459Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar The perceived adequacy of the endoscopic examination not only affects the subsequent risk of developing CRC, but also the recommendation for the screening intervals. In the United States, the Multisociety Task Force recommends flexible sigmoidoscopy at 5-year intervals because of the concern about the adequacy of the examination in the usual clinical practice, even though there is evidence to suggest that longer intervals may be adequate.25Winawer S. Fletcher R. Rex D. et al.Colorectal cancer screening and surveillance: clinical guidelines and rationale-Update based on new evidence.Gastroenterology. 2003; 124: 544-560Abstract Full Text PDF PubMed Scopus (1972) Google Scholar Two case-control studies suggest that the protective effect of sigmoidoscopy persists for at least 10 years.26Selby J.V. Friedman G.D. Quesenberry Jr., C.P. et al.A case-control study of screening sigmoidoscopy and mortality from colorectal cancer.N Engl J Med. 1992; 326: 653-657Crossref PubMed Scopus (1564) Google Scholar, 27Newcomb P.A. Storer B.E. Morimoto L.M. et al.Long-term efficacy of sigmoidoscopy in the reduction of colorectal cancer incidence.J Natl Cancer Inst. 2003; 95: 622-625Crossref PubMed Scopus (175) Google Scholar Flexible sigmoidoscopies are performed at 10-year intervals in the Colon Cancer Prevention Program of Kaiser Permanente. The Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial in the United States is evaluating flexible sigmoidoscopy every 5 years. In contrast, in Europe, once-in-a-lifetime flexible sigmoidoscopy is being evaluated in 2 clinical trials.28Benson V.S. Patnick J. Davies A.K. et al.Colorectal cancer screening: a comparison of 35 initiatives in 17 countries.Int J Cancer. 2008; 122: 1357-1367Crossref PubMed Scopus (220) Google Scholar There is evidence to suggest that benefits of colonoscopy may last longer than 10 years.29Singh H. Turner D. Xue L. et al.Risk of developing colorectal cancer following a negative colonoscopy examination: evidence for a 10-year interval between colonoscopies.JAMA. 2006; 295: 2366-2373Crossref PubMed Scopus (362) Google Scholar, 30Brenner H. Chang-Claude J. Seiler C.M. et al.Does a negative screening colonoscopy ever need to be repeated?.Gut. 2006; 55: 1145-1150Crossref PubMed Scopus (159) Google Scholar Modeling with data from the NPS suggests that the initial colonoscopy is the most important examination.31Zauber A. Winawer S.J. Lansdorp-Vogelaar I. et al.Effect of initial polypectomy versus surveillance polypectomy on colorectal cancer mortality reduction: micro-simulation modeling of the National Polyp Study.Am J Gastroenterol. 2007; 102: S558Crossref PubMed Scopus (101) Google Scholar Another recent modeling study, based on autopsy data, predicts that approximately 80% of individuals presenting with CRC between the ages of 50 and 80 already have an adenoma in their colon at age 50. In this model, the majority of CRCs can be prevented by a single colonoscopy at age 50, followed by surveillance of those with adenomas.32Geul K. Habbema J.D.F. Ting C.W. et al.Prevention of colorectal cancer by early colonoscopy: a feasible perspective, deduced from autopsy data.Gastroenterology. 2007; 132 ([abstract]): A313Google Scholar For those at average risk of developing CRC and if the initial colonoscopy is negative for colorectal neoplasia, it may be time to consider the strategy of once-in-a-lifetime colonoscopy. Currently, the United States, Germany, and Poland are among the very few countries pursuing widespread screening colonoscopy outside research protocols.28Benson V.S. Patnick J. Davies A.K. et al.Colorectal cancer screening: a comparison of 35 initiatives in 17 countries.Int J Cancer. 2008; 122: 1357-1367Crossref PubMed Scopus (220) Google Scholar Once-in-a-lifetime colonoscopy (if negative) will likely make screening colonoscopy feasible for most other countries and may provide the greatest benefit, even in countries currently pursuing screening colonoscopy because resources could then be directed toward the initial screening instead of surveillance of individuals with a low risk of CRC (and hence increase screening rates, even without additional resources). However, such strategies can only be considered if the inequities in the performance of the colonoscopies can be reduced, resulting in more uniform outcomes after the procedure. In fact, at least 2 recent population-based studies have highlighted the fact that colonoscopic screening as practiced in the community does not always provide adequate protection against CRC detection or mortality, especially for right-sided tumors.33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar, 34Baxter N.N. Goldwasser M.A. Paszat M.F. et al.Association of colonoscopy and death from colorectal cancer: a population-based case-control study.Ann Intern Med. 2009; 150: 1-8Crossref PubMed Scopus (1048) Google Scholar Singh et al,33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar in a large case-control study of colonoscopies in the California Medicaid population, found that the relative risk of CRC after a negative colonoscopy (compared with no screening) was 0.55 (95% CI, 0.16-0.65), but there were large differences between left- and right-sided lesions. The relative risk for left-sided tumors after a negative colonoscopy was 0.16 (95% CI, 0.09-0.28), whereas that for right-sided lesions was a far more modest 0.67 (95% CI, 0.51-0.88).33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar The beneficial effects of sigmoidoscopy were considerably smaller.33Singh G. Mannalithara A. Wang H.J. et al.Is protection against colorectal cancer good enough: a comparison between sigmoidoscopy and colonoscopy in the general population.Gastroenterology. 2007; 132: A81Google Scholar Baxter et al34Baxter N.N. Goldwasser M.A. Paszat M.F. et al.Association of colonoscopy and death from colorectal cancer: a population-based case-control study.Ann Intern Med. 2009; 150: 1-8Crossref PubMed Scopus (1048) Google Scholar studied the practice of colonoscopy in Ontario, Canada, in another case-control study and concluded that the beneficial effect of screening colonoscopy on mortality from CRC was confined to the left-sided tumors only. Colonoscopic CRC screening cannot eliminate all subsequent risk of developing CRC, but we can certainly improve the current effectiveness in the routine clinical practice by improving the quality of the examinations. Whether the optimal withdrawal time to allow complete visualization of colonic mucosa for an average endoscopist should be 6 or 10 minutes or another time interval still needs to be better defined. Optimal withdrawal is essential to ensure complete colonic examination. Spending 6 or 10 minutes during withdrawal is a small price to pay for improving outcomes after colonoscopy. DisclosureAll authors disclosed no financial relationships relevant to this publication. All authors disclosed no financial relationships relevant to this publication." @default.
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