Adeyinka O. Laiyemo, MD, MPH; Gwen Murphy, PhD, MPH; Paul S. Albert, PhD; Leah B. Sansbury, PhD; Zhuoqiao Wang, MS; Amanda J. Cross, PhD; Pamela M. Marcus, PhD; Bette Caan, DrPH; James R. Marshall, PhD; Peter Lance, MD; Electra D. Paskett, PhD; Joel Weissfeld, MD, MPH; Martha L. Slattery, PhD; Randall Burt, MD; Frank Iber, MD; Moshe Shike, MD; J. Walter Kikendall, MD; Elaine Lanza, PhD; Arthur Schatzkin, MD, DrPH
Grant Support: By the Intramural Research Program of the National Cancer Institute, National Institutes of Health.
Potential Financial Conflicts of Interest:Consultancies: R. Burt (Myriad Genetics), M. Shike (Stryker). Stock ownership or options (other than mutual funds): M. Shike (Stryker).
Reproducible Research Statement: Study protocol: Not available. Statistical code: Available to interested readers by contacting Dr. Laiyemo (e-mail, email@example.com). Data set: Not available.
Requests for Single Reprints: Adeyinka O. Laiyemo, MD, MPH, Cancer Prevention Fellowship Program, Biometry Research Group, Division of Cancer Prevention, National Cancer Institute, 6130 Executive Boulevard, Suite 3121, Bethesda, MD 20892; e-mail, firstname.lastname@example.org.
Current Author Addresses: Dr. Laiyemo: National Cancer Institute, 6130 Executive Boulevard, Suite 3121, Bethesda, MD 20892.
Dr. Murphy: National Cancer Institute, 6120 Executive Boulevard, Suite 7067, Bethesda, MD 20892.
Dr. Albert: National Cancer Institute, 6130 Executive Boulevard, Suite 8136, Bethesda, MD 20892.
Dr. Sansbury: National Cancer Institute, 6130 Executive Boulevard, Suite 5106, Bethesda, MD 20892.
Mr. Wang: Information Management Services Inc., 12501 Prosperity Drive, Silver Spring, MD 20904.
Dr. Cross: National Cancer Institute, 6120 Executive Boulevard, Suite 3050, Bethesda, MD 20892.
Dr. Marcus: National Cancer Institute, 6130 Executive Boulevard, Suite 3131, Bethesda, MD 20892.
Dr. Caan: Division of Research, Kaiser Permanente, 2000 Broadway, Oakland, CA 94612.
Dr. Marshall: Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263.
Dr. Lance: Arizona Cancer Center, 1515 North Campbell, Tucson, AZ 85724.
Dr. Paskett: The Ohio State University, Comprehensive Cancer Center, A356 Starling Loving, 320 West 10th Avenue, Columbus, OH 43210.
Dr. Weissfeld: Department of Epidemiology, Suite 510, Keystone Building, University of Pittsburgh, Pittsburgh, PA 15261.
Dr. Slattery: University of Utah, 375 Chipeta Way, Salt Lake City, UT 84108.
Dr. Burt: Huntsman Cancer Institute, 2000 Circle of Hope, Salt Lake City, UT 84112.
Dr. Iber: Edward Hines Jr. Hospital Veterans Affairs Medical Center, 5th and Roosevelt Road, Hines, IL 60141.
Dr. Shike: Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065.
Dr. Kikendall: Walter Reed Army Medical Center, 6900 Georgia Avenue NW, Washington, DC 20307.
Dr. Lanza: National Cancer Institute, 6116 Executive Boulevard, Suite 702, Bethesda, MD 20892.
Dr. Schatzkin: National Cancer Institute, 6120 Executive Boulevard, Suite 3040, Bethesda, MD 20892.
Author Contributions: Conception and design: A.O. Laiyemo, L.B. Sansbury, J.R. Marshall, P. Lance, M. Shike, J.W. Kikendall, E. Lanza, A. Schatzkin.
Analysis and interpretation of the data: A.O. Laiyemo, G. Murphy, P.S. Albert, L.B. Sansbury, Z. Wang, J.R. Marshall, P. Lance, M. Shike, E. Lanza.
Drafting of the article: A.O. Laiyemo, G. Murphy, L.B. Sansbury, P.M. Marcus, A. Schatzkin.
Critical revision of the article for important intellectual content: A.O. Laiyemo, G. Murphy, P.S. Albert, L.B. Sansbury, Z. Wang, A.J. Cross, P.M. Marcus, J.R. Marshall, P. Lance, E.D. Paskett, J. Weissfeld, M.L. Slattery, F. Iber, J.W. Kikendall, E. Lanza, A. Schatzkin.
Final approval of the article: A.O. Laiyemo, G. Murphy, P.S. Albert, L.B. Sansbury, Z. Wang, A.J. Cross, P.M. Marcus, B. Caan, J.R. Marshall, P. Lance, E.D. Paskett, J. Weissfeld, M.L. Slattery, R. Burt, F. Iber, M. Shike, J.W. Kikendall, E. Lanza, A. Schatzkin.
Provision of study materials or patients: B. Caan, E.D. Paskett, J. Weissfeld, M.L. Slattery, R. Burt, F. Iber, M. Shike, J.W. Kikendall.
Statistical expertise: A.O. Laiyemo, P.S. Albert, Z. Wang, J. Weissfeld.
Obtaining of funding: B. Caan, P. Lance, E.D. Paskett, R. Burt, M. Shike, E. Lanza, A. Schatzkin.
Administrative, technical, or logistic support: A.J. Cross, E.D. Paskett, M. Shike, J.W. Kikendall, E. Lanza, A. Schatzkin.
Collection and assembly of data: B. Caan, P. Lance, R. Burt, M. Shike, J.W. Kikendall, E. Lanza, A. Schatzkin.
Laiyemo A., Murphy G., Albert P., Sansbury L., Wang Z., Cross A., Marcus P., Caan B., Marshall J., Lance P., Paskett E., Weissfeld J., Slattery M., Burt R., Iber F., Shike M., Kikendall J., Lanza E., Schatzkin A.; Postpolypectomy Colonoscopy Surveillance Guidelines: Predictive Accuracy for Advanced Adenoma at 4 Years. Ann Intern Med. 2008;148:419-426. doi: 10.7326/0003-4819-148-6-200803180-00004
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Published: Ann Intern Med. 2008;148(6):419-426.
Lack of confidence in postpolypectomy surveillance guidelines may be a factor in the observed low adherence rates among providers.
To assess the 2006 postpolypectomy colonoscopy surveillance guidelines, which recommend 3-year follow-up colonoscopy for individuals with high-risk adenomas (defined as â‰¥3 adenomas or any advanced adenomas) and 5- to 10-year follow-up for patients with 2 or fewer nonadvanced adenomas, who are considered to be at low risk.
Analysis of prospective data from the Polyp Prevention Trial.
1905 patients who had colorectal adenomas removed at baseline screening or diagnostic colonoscopy and completed the trial.
Baseline adenoma characteristics, risk-stratified according to definitions used in the guidelines, were examined as predictors for advanced adenoma recurrence.
125 patients (6.6%) had advanced and 629 (33.0%) had nonadvanced adenoma recurrence; 1151 (60.4%) had no recurrence within 4 years of follow-up. The probability of advanced adenoma recurrence was 0.09 (95% CI, 0.07 to 0.11) among patients with high-risk adenomas at baseline and 0.05 (CI, 0.04 to 0.06) among those with low-risk adenomas at baseline. The relative risk for advanced adenoma recurrence for patients with high-risk adenomas versus those with low-risk adenomas at baseline was 1.68 (CI, 1.19 to 2.38) when advanced adenoma recurrence was compared with no advanced adenoma recurrence and 1.76 (CI, 1.26 to 2.46) when advanced adenoma recurrence was compared with no adenoma recurrence. The c-statistics for these 2 comparisons were 0.68 and 0.72, respectively.
Participants were self-selected and had restrictions on the degree of obesity.
Although the risk for recurrence of advanced adenoma within 4 years is greater for patients with high-risk adenomas at baseline than for those with low-risk adenomas, the discrimination of this risk stratification scheme is relatively low.
Guidelines for surveillance colonoscopy after removing a colon polyp recommend more frequent surveillance after a high-risk finding at baseline (an advanced adenoma or ≥3 adenomas).
The authors studied 1905 patients who had an adenoma at baseline colonoscopy and had follow-up colonoscopy at 1 year and 4 years. Overall, 6.6% had an advanced adenoma—considered to be high risk to become malignant—at 4 years. The advanced adenoma rates were 9% and 5% in patients with high-risk and low-risk adenomas at baseline colonoscopy, respectively.
The characteristics of an adenoma are not a reliable guide to the probability of recurrence of an advanced adenoma.
Clinical practice guidelines for postpolypectomy colonoscopy surveillance have been developed by different professional societies and updated as necessary on the basis of scientific evidence (1–4). However, surveys of gastrointestinal endoscopists (5) and primary care physicians (6, 7) have consistently shown a lack of adherence to surveillance guidelines, with repeated examinations being recommended at shorter intervals than the guidelines indicate. This suggests an overuse of surveillance colonoscopy, which already constitutes approximately 24% of procedures performed in the United States (8). Nonadherence may be due to a lack of knowledge of the guidelines, medical liability concerns, financial incentives, and differing recommendations by professional societies.
The U.S. Multi-Society Task Force on Colorectal Cancer and the American Cancer Society jointly developed and published a consensus update for postpolypectomy surveillance guidelines in 2006 to provide more consistency among guidelines (9). Patients were stratified as having high risk or low risk for subsequent development of advanced neoplasia on the basis of adenoma characteristics at baseline. The guidelines classify patients with 3 or more synchronous adenomas or any advanced adenomas (adenomas ≥1 cm in diameter or with a villous histology or high-grade dysplasia) as high risk. Individuals found to be at high risk at baseline are to have follow-up colonoscopy in 3 years, whereas those with fewer, nonadvanced, adenomatous polyps (low-risk patients) are to have repeated examination in 5 to 10 years. The guidelines recommend 10-year follow-up evaluation for average-risk individuals (those with no adenomatous polyps).
Lack of confidence in the postpolypectomy guidelines may be a common reason for nonadherence. According to Mysliwiec and colleagues (5), approximately 80% of surveyed endoscopists indicated that published evidence was very influential in their practice, but only half the respondents indicated that practice guidelines were very influential. This response highlights a perceived disconnect between published evidence and postpolypectomy guidelines. In another survey, 17% to 21% of gastroenterologists knew the guidelines but disregarded them, opting for earlier surveillance colonoscopy (10). Merritt and colleagues (11) reported that clinical practice guidelines are often fast-tracked without an adequate evaluation of their effectiveness. Therefore, validating guidelines may increase physicians' confidence and improve adherence. Our study is a step in that direction.
We sought to assess the utility of the risk-based stratification recommended by the current guidelines, using data from the dietary PPT (Polyp Prevention Trial). We measured the ability of adenoma characteristics at baseline (as defined in the 2006 consensus update on postpolypectomy surveillance guidelines) to predict subsequent advanced adenoma recurrence within 4 years.
The rationale, design, and results of the PPT are published elsewhere (12–14). In brief, the PPT was a 4-year, multicenter, randomized, controlled trial involving 2079 patients age 35 years or older who had at least 1 histologically confirmed adenoma removed during a screening or diagnostic colonoscopy within 6 months of random assignment. A total of 1663 patients reported a single reason for colonoscopy, whereas 416 had 2 or more reasons for the examination (12). Overall, approximately 9% had colonoscopy because of family history of polyps or cancer (screening), 22% for routine polyp surveillance, and 69% for diagnostic studies. The PPT sought to determine whether a low-fat, high-fiber diet affected the rate of colorectal adenoma recurrence. Patients were randomly assigned to adopt a low-fat, high-fiber diet with increased intake of fruits and vegetables or their usual diet (control). Exclusion criteria included a history of surgical resection of adenomatous polyps, bowel resection, colorectal carcinoma, the polyposis syndrome, or inflammatory bowel disease; use of lipid-lowering drugs; and body weight greater than 150% of ideal. The PPT was approved by the institutional review boards of the National Cancer Institute and each of the 8 participating clinical centers. All patients gave written informed consent. Our analysis is based on 1905 patients who completed the trial by having end point colonoscopy. The trial took place from 1991 to 1998. We included all patients in the trial because the dietary intervention had no effect on adenoma recurrence (14).
At baseline and at every annual follow-up visit, the investigators used direct interview to obtain information on each patient's demographic characteristics, health-related lifestyle, diet, and use of medication and dietary supplements. The patients had a clearing colonoscopy approximately 1 year after random assignment (1-year colonoscopy) to remove any lesion that the baseline colonoscopy missed. Patients were followed for approximately 4 years after random assignment and had a surveillance colonoscopy at the end of follow-up (4-year colonoscopy). We defined any histologically confirmed adenoma detected on colonoscopy after the 1-year colonoscopy as recurrent. For the 137 patients who did not have 1-year colonoscopy, we defined any histologically confirmed adenomatous polyps occurring at least 2 years after randomization as recurrent. We used the endoscopists' colonoscopy reports as the source for size, number, and location of polyps. Histology and degree of atypia were confirmed by 2 trial pathologists who were masked to the randomization. We defined adenomas removed from the rectosigmoid to the splenic flexure as distal and those removed from the transverse colon to cecum as proximal.
We examined adenoma characteristics at baseline as predictors of advanced adenoma recurrence for up to 3 years after clearance colonoscopy as our primary analysis, similar to that of van Stolk and colleagues (15). We repeated our analyses after including adenomas found during clearance colonoscopy, as well as the recurrent adenomas defined above, even though the National Polyp Study (16) has reported that surveillance colonoscopy at 3 years was as effective as follow-up colonoscopy at both 1 and 3 years.
We used SAS software (SAS Institute, Cary, North Carolina) for all analyses. We compared the baseline characteristics by using the t test and chi-square tests for continuous and categorical variables, respectively. We used log-binomial modeling (a binary regression model in which the probability of a recurrence is parameterized on the log scale) to assess baseline adenoma characteristics, as defined by the guidelines, as predictors of advanced adenomas through 4-year colonoscopy. This modeling method expresses association in terms of relative risks and 95% CIs. When the model did not converge, which is known to occur with log-binomial modeling, we used the SAS nonlinear programming procedure to find the maximum likelihood estimates (17). We used a Wald test to test whether the relative risks were equal to 1. We included age, sex, body mass index, nonsteroidal anti-inflammatory drug use, location of adenomas, and family history of colorectal cancer in the multivariable models. We calculated the probability of advanced adenoma recurrence as a function of baseline adenoma characteristics; this is mathematically equivalent to the positive predictive value associated with the baseline characteristics. We used the c-statistic (equivalent to the area under the receiver-operating characteristic curve) to measure discrimination (the ability of the predictive model to distinguish between patients with and those without the outcome of interest) (18, 19). The c-statistic is 0.5 if a prediction is no better than random and 1.0 for a perfectly predictive model.
For all analyses of outcome, we compared recurrence of advanced adenomas versus no recurrence of advanced adenomas and versus no adenoma recurrence. We stratified baseline adenomas by size (≥1 cm vs. <1 cm in diameter), number (≤2 vs. ≥3 adenomas, and 1, 2, or ≥3 adenomas), degree of atypia (presence or absence of high-grade dysplasia), histology (villous or tubulovillous vs. no villous characteristics), advanced versus nonadvanced, and high-risk versus low-risk at baseline.
We evaluated baseline adenoma location as distal only, proximal only, both proximal and distal, and unspecified. We excluded 41 patients from analyses involving adenoma location because the location could not be determined. Because we were interested in whether the presence of any proximal adenoma is associated with advanced adenoma recurrence, we analyzed baseline adenoma location by comparing any proximal adenoma (proximal only and both) with distal only. In another analysis of the risk associated with adenoma location, we included only patients with baseline low-risk adenomas (1 or 2 nonadvanced adenomas) and categorized them as having 1 distal, 1 proximal, 2 distal, or 2 adenomas (with at least 1 proximal adenoma).
The study was funded by the Intramural Research Program of the Center for Cancer Research and Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health; and the Division of Cancer Prevention, National Cancer Institute, National Institutes of Health. The funding source had a role in the design and reporting of the study and in the decision to submit the manuscript for publication and approved the final version of the manuscript.
Of the 2079 patients randomly assigned in the PPT, only 1905 (91.6%) completed the trial (Figure). The patients who did not complete the trial were older and more likely to have a history of smoking (Appendix Table). Table 1 shows selected baseline characteristics of patients who completed the PPT. Individuals with high-risk adenomas at baseline were slightly older and less likely to take nonsteroidal anti-inflammatory drugs. Of the patients who completed the PPT, 715 (37.5%) had advanced adenomas at baseline (Table 2); 282 (14.8%) had ≥3 adenomas and 142 (7.4%) had ≥3 adenomas of which at least 1 was advanced. At baseline, 855 patients (44.9%) had high-risk (advanced or ≥3) adenomas. A total of 1218 patients (63.9%) had 1 adenoma. One thousand thirty patients (54.1%) had only distal adenomas, and 504 (26.5%) had only proximal adenomas.
One hundred seventy-four patients did not complete the trial. Four patients were excluded late (no baseline adenoma), 88 died before the end of the trial (from causes unrelated to the trial), and 82 withdrew (72 did not have follow-up colonoscopy, 9 declined to participate, and 1 withdrew because of ill health).
During follow-up, 1151 patients (60.4%) had no adenoma recurrence, 125 (6.6%) had advanced adenoma, and 629 (33.0%) had nonadvanced adenoma at follow-up. Patients with adenoma recurrence were older and predominantly male (data not shown).
The probability of advanced adenoma recurrence was 0.09 (95% CI, 0.07 to 0.11) among patients with baseline high-risk adenoma and 0.05 (CI, 0.04 to 0.06) among those with baseline low-risk adenoma, as defined by current guidelines. The recurrence rates were similar for both definitions of high-risk adenoma: 0.09 (CI, 0.07 to 0.11) among those with baseline advanced adenomas and 0.10 (CI, 0.07 to 0.14) among those with 3 or more adenomas at baseline (Table 2). In analyses with 1 baseline adenoma characteristic in each regression model (Table 2), the presence of 1 or more advanced adenomas, size 1 cm or greater, high-grade dysplasia, and villous histology were each associated with advanced adenoma recurrence regardless of the comparison group, whereas the presence of 3 or more adenomas was a risk factor only when the comparison group was no adenoma recurrence. However, the predictive ability of the log-binomial models with these baseline adenoma characteristics is relatively low. The c-statistics for the models ranged from 0.67 to 0.73. A c-statistic of 0.7 is considered to have limited discriminatory ability, whereas a c-statistic greater than 0.8 has discrimination thought to be adequate for real clinical utility (20).
In multivariable analyses that included all individual baseline adenoma characteristics in the model, only villous histology and proximal location were independent predictors of advanced adenoma recurrence in the primary analysis, which used only the 4-year colonoscopy data (Table 3). The c-statistics for the multivariable models were 0.71 and 0.74. The results were similar when we included 1-year colonoscopy as well as 4-year colonoscopy results in our analysis, except that polyp size of 1 cm or greater became a significant risk factor for advanced adenoma recurrence when no advanced adenoma recurrence was used as the reference group (relative risk, 1.56 [CI, 1.13 to 2.14]) but not when no adenoma recurrence was the comparison category (relative risk, 1.25 [CI, 0.92 to 1.69]). The c-statistics for the multivariable models were 0.69 when advanced adenoma was compared with nonadvanced adenoma recurrence and 0.73 when advanced adenoma was compared with no adenoma recurrence.
Patients with proximal adenomas at baseline were less likely than patients with only distal adenomas at baseline to have large (≥1 cm) adenomas at baseline (25.8% vs. 37.7%; P < 0.001), villous histology (16.4% vs. 23.8%; P < 0.001), high-grade dysplasia (5.7% vs. 9.5%; P = 0.002), and advanced adenoma (32.0% vs. 43.3%; P < 0.001). Proximal adenomas at baseline were associated with advanced adenoma recurrence during follow-up in all models. We subsequently evaluated the effect of proximal location on advanced adenoma recurrence among patients with low-risk adenomas (1 or 2 nonadvanced adenomas) at baseline. The presence of 2 adenomas with at least 1 in the proximal colon was significantly associated with an increased risk for advanced adenoma recurrence (relative risk, 2.62 [CI, 1.29 to 5.29]) compared with 1 distal adenoma (Table 4). The c-statistics for all predictive models in our analyses ranged from 0.64 to 0.74.
In our study, only the villous histology component of the definition of an advanced adenoma was an independent predictor at baseline of recurrent advanced adenomas within 4 years. Adenoma size, high-grade dysplasia, and presence of 3 or more synchronous nonadvanced adenomas were not independent risk factors. Overall, we found the current postpolypectomy guidelines to have limited predictability for advanced adenoma recurrence within 4 years, even when individual baseline adenoma characteristics were statistically significant risk factors.
In addition, patients with 2 nonadvanced adenomas were at increased risk for advanced adenomas if they had any proximal adenoma. The current postpolypectomy guidelines do not make any surveillance recommendations based on adenoma location at baseline. However, when we incorporated adenoma location into the definition of baseline high-risk adenoma, the probability of advanced adenoma recurrence with this new high-risk definition was 0.09 (CI, 0.07 to 0.11), compared with 0.04 (CI, 0.03 to 0.06) for the new low-risk category. The relative risk estimates were 2.02 (CI, 1.38 to 2.96) and 2.12 (CI, 1.46 to 3.07), but the c-statistic for the multivariable models remained only 0.68 and 0.71 for distinguishing recurrence of advanced adenomas versus no recurrence of advanced adenomas and no adenoma recurrence, respectively. Therefore, inclusion of another baseline adenoma characteristic associated with a statistically significant relative risk for recurrence did not materially improve the limited predictability that we observed in the current guidelines' risk stratification scheme.
We evaluated the diagnostic accuracy of the multivariable risk models (which incorporated baseline adenoma and demographic variables) for predicting advanced adenoma recurrence, thereby assessing the utility of the current postpolypectomy guidelines. Our study suggests that statistically significant risk factors—both adenoma features and demographic and lifestyle characteristics—do not necessarily translate into clinically useful predictive guidelines. If other studies confirm our findings, a review of the postpolypectomy guidelines to improve their ability to predict recurrence of important colorectal lesions may be warranted.
Many of our findings confirm those from other studies. The 39.6% overall rate of adenoma recurrence in our study was similar to that in previous reports, which ranged from 35% to 48.6% at 3 to 4 years (15, 16, 21–25). Unlike previous investigations (16, 26, 27), we did not find multiple adenomas at baseline to be a risk factor for subsequent advanced adenomas; however, similar to other studies (28, 29), we did find that an advanced adenoma at baseline was a risk factor—albeit one with limited predictability.
In a recent study by Lieberman and colleagues (30), 895 patients with neoplasia detected on screening colonoscopy and 298 neoplasia-free control participants from a Veterans Affairs population were followed for approximately 5.5 years and had repeated colonoscopy during this period. After adjustment for age and family history of colorectal cancer, the investigators found that adenoma size of 1 cm or greater, villous adenoma, and high-grade dysplasia were associated with an increased risk for advanced adenoma recurrence compared with participants without adenomas at baseline. For most baseline adenoma characteristics, Lieberman and colleagues (30) reported slightly higher probabilities of advanced adenoma recurrence than we found: 1 or 2 adenomas regardless of histology, 6.5% versus 6.0%; adenoma size of 1 cm or greater, 15.5% versus 7.9%; villous adenoma, 16.1% versus 12.2%; and high-grade dysplasia, 17.4% versus 10.3%. The exception was 1 or 2 nonadvanced adenomas at baseline, for which we and Lieberman and colleagues found a similar probability (4.9% vs. 4.6%, respectively). On the basis of high-risk adenoma characteristics, the probability of advanced adenoma recurrence in Lieberman and colleagues' sample ranged from 0.12 to 0.17 through 5.5 years of follow-up; this range is similar to ours (0.08 to 0.12).
Although the PPT was a dietary intervention trial, it provided an opportunity to investigate baseline factors associated with adenoma recurrence in a large population. Studying the PPT population contributed several potential strengths. The PPT is a large, randomized, controlled trial in which all patients had at least 1 baseline adenoma removed during colonoscopy; trial pathologists were used; information on candidate risk factors was prospectively gathered; and all patients had planned colonoscopic assessment for recurrence after 4 years of follow-up.
However, our study also has limitations. Participants in the PPT were self-selected and may have been healthier than similar members of the general population (the healthy volunteer effect). First, because the PPT studied a specific dietary pattern, the investigators excluded patients who needed to follow a strict dietary regimen, such as diabetics, and those with cholesterol levels high enough to require medication. Second, the design of the PPT excluded people who weighed more than 150% of their ideal body weight. This exclusion affects the generalizability of our results, because obesity may be associated with an increased risk for adenoma recurrence (31). Finally, the PPT population had clearing colonoscopies approximately 1 year after random assignment to remove missed lesions from qualifying colonoscopy; adenoma recurrence in our study may therefore be lower than that in usual practice.
The focus of colonoscopy guidelines should be to identify individuals at the highest risk and target them for surveillance, similar to the risk prediction recommendations for cardiovascular disease (32). Our study suggests that the adenoma-based risk stratification used in the current postpolypectomy surveillance guidelines have limited predictability for advanced adenoma recurrence. Misclassification of high-risk patients as low-risk may lead to missing potentially preventable colorectal cancer, and misclassification of low-risk patients as high-risk may impose further burden on our limited endoscopic resources. To achieve the overarching goals of practice guidelines—widespread adoption of recent clinical advances, improvement in quality of care through reduction in inappropriate practice pattern variation, and promotion of health care cost-effectiveness (11, 33, 34)—we need to improve the predictive ability of the guidelines' recommendations.
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Douglas K. Rex
Indiana University Hospital
April 18, 2008
Post-polypectomy Surveillance Guideline
To the editors,
Laiyemo et al were critical of the discriminatory value of current post-polypectomy surveillance guidelines (1). The history of post- polypectomy practice has been to expand intervals, first from 1 to 3 years, then from 3 to 5 years in the cohort considered at lowest risk. The rationale for interval expansion is that surveillance has risk, cost, and less value in preventing cancer than baseline clearing examinations (2). We are concerned that colonoscopists will react to Laiyemo et al's findings by shortening intervals.
Several factors warrant comment. First, the guideline was based on the totality of literature relating baseline colonoscopy findings to subsequent advanced neoplasia (3). Contrary to the accompanying editorial claiming that the guideline is based on 5 studies, we identified and summarized 12 relevant studies (3). No predictor of higher risk was found in all studies (3). This may reflect that multiplicity of baseline adenomas depends on efficacy of clearing (4), that polyp size is subject to endoscopist interpretation, and that villous elements and high grade dysplasia are subject to marked interobserver variation. Thus, no single study (1) would be expected to confirm each risk factor in the guideline or to represent a definitive study. Second, the guideline does not recommend major differences in follow-up for higher vs lower risk baseline findings, consistent with mixed evidence. Thus, patients with higher risk findings are recommended to undergo colonoscopy at 3 years, and the lower risk group at 5 to 10 years. Most of the latter group undergoes colonoscopy at <= 5 years in the U.S. Third, while advanced adenomas are an accepted surrogate endpoint, they do not kill people. Shortening intervals from 5 years to 3 years to detect a 5% incidence of advanced adenomas in a lower risk cohort will not clearly reduce cancer incidence or deaths at acceptable cost and risk.
The principle limitation to the effectiveness of any surveillance guideline is variability between endoscopists in effectiveness of baseline clearing (4,5). We emphasized the importance of quality baseline examinations in the guideline (3). We believe that much more can be gained in efficacy, safety and cost reductions by improving the quality of baseline examinations than by shortening post-polypectomy intervals in patients for whom the totality of the literature indicates a low risk of advanced neoplasia over 5 years or longer.
Douglas K Rex M.D., FACP, Indiana University School of Medicine, Indianapolis, Indiana
Sidney J Winawer, M.D., FACP, Memorial Sloan-Kettering Cancer Center, New York, New York
1. Laiyemo AO, Murphy G, Albert PS, Sansbury LB, Wang Z, Cross AJ, Marcus PM, Caan B, Marshall JR, Lance P, Paskett ED, Weissfeld J, Slattery ML, Burt R, Iber F, Shike M, Kikendall JW, Lanza E, Schatzkin A. Postpolypectomy colonoscopy surveillance guidelines: predictive accuracy for advanced adenoma at 4 years. Ann Intern Med 2008;148:419-26.
2. Zauber A, Winawer SJ, Lansdorp-Vogelaar I, van Ballegooijen M, O'Brien MJ. 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:S558.
3. Winawer SJ, Zauber AG, Fletcher RH, Stillman JS, O'Brien MJ, Levin B, Smith RA, Lieberman DA, Burt RW, Levin TR, Bond JH, Brooks D, Byers T, Hyman N, Kirk L, Thorson A, Simmang C, Johnson D, Rex DK. Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society. Gastroenterology 2006;130:1872-85.
4. Chen SC, Rex DK. Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy. Am J Gastroenterol 2007;102:856-61.
5. Barclay RL, Vicari JJ, Doughty AS, Johanson JF, Greenlaw RL. Colonoscopic withdrawal times and adenoma detection during screening colonoscopy. N Engl J Med 2006;355:2533-41.
Adeyinka O. Laiyemo
National Cancer Institute
May 7, 2008
Predictive accuracy of the postpolypectomy guidelines - authors' reply
We agree with Drs. Rex and Winawer that a single study is unlikely to be definitive, especially when, as they suggest, variability in clinician judgment influences the identified predictors of higher risk for advanced adenoma.
We did not, however, recommend shortening the interval of surveillance colonoscopy for the low-risk category (1). In our study, the advanced adenoma recurrence rate was 9% among the high-risk and 5% among the low-risk category at 4 years. The c-statistics from multivariate models incorporating demographic and lifestyle factors with adenoma characteristics indicated that there was not much discrimination between the 2 risk groups. Although, these finding may be interpreted as meaning we should screen both groups at 3 years, they could just as well be viewed as suggesting we should extend the surveillance interval for both groups to 5 years.
Given the cost and risk associated with colonoscopic surveillance, the challenge becomes developing interval surveillance recommendations based on risk categorization schemes with greater predictive capacity. Combining the data from completed and ongoing adenoma trials and observational studies may help achieve this goal, especially if we conduct multivariate analyses incorporating demographic and lifestyle information along with adenoma characteristics. Whether additional colonoscopy- adenoma studies are needed to achieve the desired predictability for risk assignment remains to be seen.
Adeyinka O. Laiyemo, MD, MPH Cancer Prevention Fellowship Program, Office of Preventive Oncology and Division of Cancer Prevention, National Cancer Institute
Elaine Lanza, PhD Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute
Arthur Schatzkin, MD, DrPH Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute
1. Laiyemo AO, Murphy G, Albert PS, Sansbury LB, Wang Z, Cross AJ, et al. Postpolypectomy surveillance guidelines: predictive accuracy for advanced adenoma at 4 years. Ann Intern Med. 2008;148:419-26. [PMID: 18347350].
Gastroenterology/Hepatology, Hematology/Oncology, Colonoscopy/Sigmoidoscopy.
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