Use of colonoscopy for polyp surveillance in Medicare beneficiaries


  • Gregory S. Cooper MD,

    Corresponding author
    1. Division of Gastroenterology, University Hospitals Case Medical Center, Case Western Reserve University and Case Comprehensive Cancer Center, Cleveland, Ohio
    • Division of Gastroenterology, University Hospitals Case Medical Center, 11100 Euclid Avenue, Cleveland, OH 44106-5066

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    • Fax: (216) 983-0347

  • Tzuyung D. Kou PhD,

    1. Division of Gastroenterology, University Hospitals Case Medical Center and Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, Ohio
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  • Jill S. Barnholtz Sloan PhD,

    1. Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio
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  • Siran M. Koroukian PhD,

    1. Department of Epidemiology and Biostatistics, and Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio
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  • Mark D. Schluchter PhD

    1. Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio
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  • The linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database was used in this study. The interpretation and reporting of these data are the sole responsibility of the authors. The authors acknowledge the efforts of the Applied Research Program, National Cancer Institute; the Office of Research, Development, and Information, Centers for Medicare and Medicaid Services; Information Management Services, Inc.; and the SEER Program tumor registries in the creation of the SEER-Medicare database.



Professional society guidelines recommend follow-up colonoscopy for patients with resected colonic adenomas. However, adherence to guideline recommendations in routine clinical practice has not been well characterized.


The authors used a population-based sample of Medicare beneficiaries to identify all patients aged ≥70 years who had a claim for colonoscopy with polypectomy or hot biopsy during the period from 2001 to 2004. Medicare claims through 2009 identified colonoscopy within the following 5 years as well as fecal occult blood testing, sigmoidoscopy, and barium enema.


In total, 12,771 patients were included. At 5 years, 45.7% of patients underwent another colonoscopy, and 32.3% of procedures included a polypectomy. The rates of fecal occult blood testing, flexible sigmoidoscopy, and barium enema at 5 years were 54%, 3.8%, and 2.9%, respectively. There was a marked decrease in repeat colonoscopy at 1 year, 3 years, and 5 years with more recent years of index procedures. Other predictors of undergoing repeat colonoscopy were younger age, African American race, and a colonoscopy before the index examination. There was no association with physician specialty. The decreasing use of colonoscopy with time was maintained in a multivariable analysis.


In a sample of elderly Medicare beneficiaries, there was under use of follow-up colonoscopy at 5 years after polypectomy, and <50% of patients received a repeat examination. In particular, the use of this procedure decreased over the 4-year study period. Coupled with other data indicating the overuse of follow-up colonoscopy in patients without polyps, there appeared to be significant discordance between guidelines and actual practice. Cancer 2013. © 2013 American Cancer Society.


Colorectal cancer is currently the second leading cause of cancer mortality in the United States, accounting for approximately 52,000 deaths and 152,000 new cases annually.1 It is believed that the vast majority of colorectal cancers arise from colon adenomas,2 which are present is as many as 40% of patients in the targeted ages for colorectal cancer screening.

In addition to screening, patients who have adenomas removed at an index colonoscopy typically are referred for follow-up colonoscopies at a more frequent time interval than patients without adenomas. The goal of these examinations, termed surveillance, is to detect recurrent adenomas or polyps that were missed at the time of the initial colonoscopy. Colonoscopies for polyp surveillance as frequently as every 2 years have been reimbursed under Medicare since 1998 and have been recommended by clinical practice guidelines since 1997.3 The specific intervals recommended by guidelines generally have been extended in more recent versions; however, for most patients, a follow-up interval of 5 years is prescribed.4 These recommendations are supported by the National Polyp Study, which provided evidence that longer follow-up intervals were equally effective in detecting recurrent or missed polyps.5 More frequent intervals may be justified among patients with advanced adenomas, defined as polyps that measure >1 cm in greatest dimension or that contain focal high-grade dysplasia or villous features,4 because it is believed that these polyps have a higher rate of progression to cancer.6

Despite recommendations for postpolypectomy follow-up, there is evidence that clinicians may not adhere to practice guidelines. Surveys of practicing endoscopists7 and primary care physicians who refer patients for colonoscopy8 suggest that physicians may perform surveillance in excess of guidelines. In contrast, a recently published study that used Medicare claims data reported that 46% of average-risk patients who underwent a colonoscopy that was negative for polyps underwent a repeat examination within 7 years.9 In a recent audit of postpolypectomy follow-up practices in the Prostate, Lung, Colorectal, and Ovarian Cancer screening trial, the cumulative probability of a surveillance colonoscopy within 5 years was 58% for patients with an advanced adenoma and 26% for patients with no adenomas, suggesting discordance from guidelines.10

Given the evidence that receipt of follow-up colonoscopy may be discordant from practice guidelines, we conducted the current study in a population-based cohort to ascertain the use of surveillance colonoscopy among patients with a history of colonic polyps. We hypothesized that a significant proportion of patients receive follow-up colonoscopy in excess of recommended guidelines and that receipt would be associated with patient and endoscopist factors.


Data Sources

Data for this study were obtained from a noncancer sample of the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database, which was developed in the 1990s as a large population-based source of information for epidemiological and health services research.11, 12 The files consist of a 5% random sample of Medicare beneficiaries without cancer who reside in 1 of the geographic areas contained in the SEER registries. The SEER Program captures approximately 26% of the US population; and, within each registry, approximately 93% of patients aged >64 years are included.

Medicare claims are contained in 3 different files, the Carrier file, which includes provider claims; the Outpatient file, which includes claims from institutional outpatient providers; and the Medicare Provider Analysis and Review (MEDPAR) files, which include all hospitalizations. Each Medicare claim contains diagnoses coded by the International Classification of Diseases, ninth revision, Clinical Modification (ICD-9-CM), and procedures coded according to Common Procedural Terminology, fourth edition (CPT-4) or the ICD-9-CM. The Carrier and Outpatient claims also include physician specialty codes and an encrypted version of the physician's unique personal identifier (UPIN), which also was used to categorize practitioners according to specialty. In addition to Medicare claims, we used the Summarized Denominator (SUMDENOM) file, which contains demographic, enrollment, and entitlement information, and the ZIP Code Census File, which includes selected sociodemographic information at the ZIP code level from the 2000 Census.

The cohort of patients undergoing colonoscopy with polypectomy was identified using the 2001 through 2004 Medicare Carrier, Outpatient, and MEDPAR files. These years were selected because they include a period during which colonoscopy was reimbursed through Medicare and allowed for a minimum of 5 years of follow-up in all patients. Patients were eligible if they were aged ≥70 years (to allow ascertainment of procedure use in the previous 5 years) and were receiving Medicare benefits through Part A and Part B over the entire study period. Patients who were enrolled in Medicare-sponsored managed-care plans during the period from 1997 to 2009 were excluded because of the high likelihood of incomplete claims. Patients who had a diagnosis code for carcinoma in situ (codes 230.3 and 230.4) within 6 months (before or after) of the index colonoscopy also were excluded from the analysis. Because of the different biologic mechanisms of colon cancer and the goals of surveillance, patients with inflammatory bowel disease (ulcerative colitis and Crohn disease) were excluded. Finally, to obtain a cohort that had complete examinations in which follow-up guidelines were more uniform, examinations that were designated incomplete were excluded. Follow-up among surviving patients occurred through the end of 2009.

All claims for colonoscopy with polypectomy were identified by procedure codes for 1 or more of the following: colonoscopy with snare polypectomy (CPT-4 44393, 44394, 45383, and 45385; ICD-9-CM codes 45.42, 45.43, and 48.36), which includes both snare cautery and “cold snare” polypectomy; colonoscopy with hot biopsy of polyp (CPT-4 codes 44392 and 45384); and colonoscopy with ablation of polyps (eg, argon plasma coagulation; CPT-4 code 45383). These codes were selected based on the results from preliminary studies and previous surveys of endoscopists13 indicating that they have a high positive predictive value for the presence of a larger polyp, which is much more likely to be adenomatous. Patients were followed from the index colonoscopy through the earliest of the following events: second colonoscopy, bowel resection, death, 5-year interval after the initial examination, or the end of calendar year 2009.

Demographic characteristics, including age, sex, and race, were obtained from the SUMDENOM file. Medicare claims from the previous 5 years were searched for procedure codes for colonoscopy. Claims from the previous 5 years through the index colonoscopy date were searched for a diagnosis that constituted increased neoplasia risk or a prior history of polyp removal. These criteria included codes for a personal history of colon polyps (V12.72), family history of gastrointestinal neoplasm (code V16.0), benign neoplasm (polyp) of colon (code 211.3) or rectum (code 211.4), and previous colonoscopy or sigmoidoscopy with polypectomy (CPT-4 codes 44392, 44393, 44394, 45333, 45338, 45339, 45383, 45384, and 45385; ICD-9-CM codes 45.42, 45.43, and 48.36). Diagnosis codes according to the ICD-9-CM during the 365 day to the 30-day interval (total, 11 months) before the index colonoscopy were searched to derive a previously validated, weighted comorbidity index.14

In addition, MEDPAR, Carrier, and Outpatient files from the date of the index colonoscopy through the end of follow-up were searched for the presence of claims for other colorectal procedures including fecal occult blood testing (FOBT), flexible sigmoidoscopy, and barium enema. As a proxy for individual-level measures, which were unavailable in Medicare, the ZIP Code Census files contained ecologic measures of socioeconomic status. Relevant measures at the time of the index colonoscopy included median income and the proportion of individuals aged ≥25 years with a high school diploma. Measures for each patient in the cohort at the time of the index colonoscopy were rank ordered and divided into quartiles according to rank.

Geographic regions were divided into Northeast, South, Midwest, and West. By using the encrypted UPIN and Medicare specialty codes, physician specialty at the index colonoscopy was coded as gastroenterology, colorectal surgery, general surgery, internal medicine, family medicine, or unknown.


The major outcome of interest was repeat colonoscopy within 5 years of the index procedure. Given the variable length of follow-up because of death or disenrollment, we used Kaplan-Meier analysis. We also used Kaplan-Meier analysis to measure colonoscopy use at 1 year and 3 year of follow-up as well as the use of FOBT, flexible sigmoidoscopy, and barium enema. Variables that were examined for their association with repeat colonoscopy included demographic characteristics, geographic region, comorbidity, colonoscopy before the index examination, endoscopist specialty, and small area socioeconomic measures.

The log-rank test was used to examine the association of individual variables with receipt of colonoscopy at 1 year, 3 years, and 5 years. We then used a multivariable Cox proportional hazards model to determine the independent association of individual covariates with the time to repeat colonoscopy. Because the major outcome of interest was receipt of colonoscopy at 5 years, we censored all patients beyond 5 years of follow-up. In a secondary analysis, we also examined factors associated with FOBT use at 5 years. The protocol was approved by the Institutional Review Board of University Hospitals Case Medical Center.


From the Medicare data files, we identified 33,094 patients who underwent colonoscopy with polypectomy during the period from 2001 to 2004. Patients were excluded for the following nonmutually exclusive reasons: age <70 years (n = 15,511), lack of enrollment in Medicare Parts A and B (n = 842), enrollment in Medicare managed care plans (n = 3984), a diagnosis of inflammatory bowel disease (n = 227), and a diagnosis of carcinoma in situ (n = 34). The remaining 12,771 patients comprised the study cohort (Table 1). Consistent with the demographics of the older Medicare population, the mean age of the sample was 78.1 ± 5.0 years, 56.3% were women, and 86.4% were Caucasian. Most patients had comorbidity scores of zero, 24.6% had additional cancer risk factors (prior polyp, family history), and 22.4% underwent at least 1 colonoscopy before the index examination. Gastroenterologists performed the index colonoscopy in 65% of patients, and the procedure included 1 or more of snare polypectomy in 84.5%, hot biopsy in 14.7%, and ablation of polyps in 3.5%.

Table 1. Factors Associated With Repeat Colonoscopy at 1 Year, 3 Years, and 5 Years in 12,771 Medicare Beneficiaries
VariableNo. (%)Colonoscopy Year 1, %PColonoscopy Year 3, %PColonoscopy Year 5, %P
  • a

    Increased risk includes prior history of polyps, or family history of cancer.

Age group, y       
 70-744050 (31.7)6.9.1725.3.3750.5<.0001
 75-794666 (36.5)7.7 26.7 47.3 
 80-842697 (21.1)8.9 25.4 42.7 
 ≥851358 (10.6)9.6 22.6 31.4 
 Women7196 (56.3)8.0224.7.0343.6.0001
 Men5575 (46.7)7.8 27.2 49.5 
 White11,036 (86.4)7.6.00225.4.000946.2.02
 Black666 (5.2)11.3 34.3 53.8 
 Other847 (6.6)9.1 25.7 42.6 
 Unknown222 (1.7)7.7 25.6 48.3 
Procedure year       
 20013240 (25.4)9.3.000434.7<.000157.4<.0001
 20023412 (26.7)7.9 26.3 48.6 
 20033270 (25.6)7.9 22.5 42.7 
 20042849 (22.3)6.4 19.1 36.2 
No. of comorbidities       
 07063 (55.3)7.2.000424.6<.000145.8.38
 13389 (26.5)7.9 26.3 47.7 
 ≥22319 (18.2)10 29.2 45.3 
Increased riska       
 Yes3139 (24.6)7.9.8932.8<.000161.3<.0001
 No9632 (75.4)7.9 23.6 41.2 
Prior colonoscopy       
 Yes2863 (22.4)8.6.00335.6<.000165.3<.0001
 No9908 (77.6)7.7 23.2 41.2 
 Gastroenterology8288 (64.9)7.7.1225.5.0246.1.17
 Family medicine1558 (12.2)8.9 30.5 53.5 
 Internal medicine1226 (9.6)8.8 29.2 45.1 
 General surgery1060 (8.3)6.8 26.0 42.1 
 Colorectal surgery243 (1.9)8.1 24.9 50.3 
Unknown396 (3.1)7.8 18.7 48.9 
Geographic region       
 Northeast3697 (28.9)7.4<.0000125.7.00246.1<.0001
 South2060 (16.1)8.6 31.1 53.5 
 Midwest1431 (11.2)7.5 24.6 45.2 
 West4112 (32.2)7.6 23.2 42.1 
 Other1471 (11.5)9.0 27.5 50.3 
Income quintile       
 First3113 (24.4)8.9<.000128.8.0148.2.06
 Second3130 (24.5)8.3 26.5 46.8 
 Third3120 (24.4)7.1 23.4 44.3 
 Fourth3125 (24.5)7.4 25.1 45.7 
Education quintile       
 First3122 (24.4)8.9.0229.2.00748.3.15
 Second3119 (24.4)7.4 26.1 44.5 
 Third3123 (24.5)8.5 25.2 46.8 
 Fourth3124 (24.5)6.9 23.6 45.3 

Among the eligible patients in the cohort, 7.9% underwent colonoscopy within 1 year of follow-up, 25.5% underwent a colonoscopy within 3 years, and 45.7% underwent colonoscopy within 5 years (Fig. 1). The follow-up colonoscopy was diagnostic (no procedure or biopsy alone) in 67.7% and included polypectomy in 32.3%. The use of barium enema and flexible sigmoidoscopy at 5 years was low (2.9% and 3.8%, respectively), but FOBT was used commonly (16.4% at 1 year, 42.1% at 3 years, 54% at 5 years).

Figure 1.

This Kaplan-Meier curve illustrates the proportion of patients with previous polypectomy that underwent repeat colonoscopy in follow-up stratified according to the presence or absence of previous risk factors for neoplasia (prior polyp, family history of colon cancer). There was significantly greater use of colonoscopy for patients who had risk factors (P < .0001).

Predictors of colonoscopy receipt are listed in Table 1. In general, patients with more comorbidities were more likely to receive colonoscopy early in the follow-up period, and advanced age was associated with a lower cumulative rate at 5 years. Men were more likely to undergo colonoscopy in years 3 and 5, and African Americans were more likely to undergo colonoscopy at all 3 time points. Repeat procedures were also more common in patients who underwent colonoscopy before the index examination and in patients who had additional cancer risk factors (Fig. 1). Among patients who had a prior diagnosis of colon polyps and/or a family history of cancer, the frequency of surveillance was 7.9%, 32.8%, and 61.3% at 1 year, 3 years, and 5 years, respectively, compared with 7.9%, 23.6%, and 41.2% in others. The frequency of repeat colonoscopy was highest in the southern United States, but there were no consistent differences in colonoscopy receipt according to endoscopist specialty or socioeconomic factors. It is noteworthy that the frequency of repeat colonoscopy decreased significantly in more recent periods (Fig. 2). For example, the rate of 5-year colonoscopy decreased from 57.4% for index procedures performed in 2001 to 36.2% for procedures performed in 2004.

Figure 2.

These Kaplan-Meier curves illustrate the receipt of repeat colonoscopy after polypectomy stratified by year of the index polypectomy. The frequency decreased with later years of the index colonoscopy (P < .0001).

The results of the multivariable proportional hazards analysis are provided in Table 2. Independent predictors of repeat colonoscopy at 5 years included younger age, male gender, a diagnosis of colon polyps or other risk factors before the index examination, and a colonoscopy before the index examination. Like in the univariate analysis, the likelihood of repeat colonoscopy within 5 years decreased in more recent time periods. Compared with 2001, the hazard ratio of undergoing repeat colonoscopy for 2004 index procedures was 0.61 (95% confidence interval [CI], 0.55-0.68).

Table 2. Multivariable Analysis for Predicting Repeat Colonoscopy at Five Years
VariableHR (95% CI)
  1. Abbreviations: CI, confidence interval; HR, hazard ratio.

Age group, y 
 75-790.95 (0.89-1.02)
 80-840.89 (0.82-0.97)
 ≥850.70 (0.62-0.80)
 Women0.90 (0.84-0.97)
 Black1.21 (1.02-1.44)
 Other/unknown1.19 (0.89-1.59)
Procedure year 
 20020.82 (0.74-0.91)
 20030.72 (0.65-0.80)
 20040.61 (0.55-0.68)
No. of comorbidities 
 11.01 (0.94-1.09)
 ≥21.05 (0.96-1.15)
Increased risk 
 Yes1.47 (1.31-1.66)
Prior colonoscopy 
 Yes1.23 (1.09-1.38)
 Family medicine1.15 (0.96-1.38)
 Internal medicine1.09 (0.95-1.24)
 General surgery1.02 (0.85-1.21)
 Colorectal surgery1.04 (0.95-1.13)
 Unknown1.23 (1.00-1.52)
Geographic region 
 South1.16 (1.03-1.32)
 Midwest0.96 (0.83-1.11)
 West0.93 (0.83-1.04)
 Other1.13 (0.99-1.30)
Income quintile 
 Second1.04 (0.93-1.16)
 Third0.98 (0.87-1.10)
 Fourth1.02 (0.90-1.14)
Education quintile 
 Second0.91 (0.81-1.02)
 Third0.99 (0.88-1.11)
 Fourth1.00 (0.88-1.14)

In a secondary analysis, we examined factors that were associated with FOBT at 5 years. In a univariate analysis, older age and increased comorbidity were inversely associated with FOBT use (ages 75-79 years: odds ratio [OR], 1.03; 95% CI, 0.94-1.12; ages 80-84 years: OR, 0.89; 95% CI, 0.80-0.99; aged ≥85 years: OR, 0.69; 95% CI, 0.60-0.79) and with comorbidity scores (1 comorbidity: OR, 0.88; 95% CI, 0.81-0.96; ≥2 comorbidities: OR, 0.70; 95% CI, 0.63-0.77). Similar to what we observed with colonoscopy, the use of FOBT declined with more recent years of the index colonoscopy (2002: OR, 0.94; 95% CI, 0.85-1.03; 2003: OR, 0.79; 95% CI, 0.72-0.88; 2004: OR, 0.66; 95% CI, 0.59-0.73). None of the other patient or provider factors were associated with FOBT.


Colonoscopy is a commonly recommended procedure for screening in the asymptomatic at-risk population as well as for the follow-up or surveillance of patients with adenomatous polyps. Studies that have included medical record review,15 data from clinical trials,10, 16 and surveys of endoscopists7 and referring physicians8 all have reported discordance between guideline recommendations and surveillance practices. In addition, the findings of a recently published study that used Medicare claims data9 were suggestive of the overuse of follow-up colonoscopy in polyp-free individuals. The current study, which also included Medicare data, highlights another problem with colonoscopic practice: the under use of surveillance in patients with polyps. We observed that <50% of eligible patients underwent repeat colonoscopy within 5 years, a rate that was even lower than in previous studies. The frequency also appeared to diminish with more recent study years. This is a patient population believed to be at increased risk for development of advanced neoplasia and colorectal carcinoma; thus, more frequent colonoscopic intervals than the average-risk population are recommended. Indeed, we observed that >30% of the follow-up colonoscopies included polypectomy, suggesting a relatively high yield of surveillance in this patient population. We also noted that the frequency of a nonrecommended surveillance procedure, FOBT, exceeded that of colonoscopy. The latter practice is not recommended by guidelines and would serve little purpose in the detection of recurrent polyps.

Our study also indicated a somewhat greater frequency of polyp surveillance in African Americans, which differs from lower reported rates of screening colonoscopy in the general Medicare population17 and in beneficiaries undergoing surveillance colonoscopy after cancer resection.18 The underlying reasons for this difference are not evident but potentially may be attributed to more advanced polyp characteristics in African Americans. These factors, which were not available in the database, may be associated with earlier recall for surveillance. The differences in surveillance use among SEER regions also are consistent with other studies in colon cancer survivors18 as well as in the general Medicare population.19, 20 The potential reasons for geographic variation probably are multifactorial; however, because surveillance colonoscopy is universally reimbursed, local practice patterns are likely important.

The underlying reasons for the under use of surveillance probably are multifactorial and cannot be ascertained from this database. First, it is possible that, because of changes in providers and/or imperfect communication systems, endoscopist recommendations from the initial colonoscopy were not disseminated to the patient's primary physician. Second, for certain patient groups, such as the extreme elderly or patients with multiple comorbidities, the perceived benefit of repeat colonoscopy in prolonging life may have been limited.21 In contrast to the US Preventive Services Task Force screening guidelines, in which an upper age limit of 75 years is recommended for routine colorectal screening,22 similar guidelines do not exist for polyp surveillance. Our data used a previously validated comorbidity index,14 but Medicare claims do not include other measures of performance status such as frailty. There is also a higher risk of procedural complications in older individuals and in patients with greater comorbidity23; and for these reasons, endoscopists may have been reluctant to recommend surveillance. Third, the findings of a decreased frequency of 5-year surveillance over time may have reflected changes in guidelines to some extent. Through 2003,3 guidelines recommended a 5-year surveillance interval for single, small (<1 cm), tubular adenomas and a 3-year follow-up for all others. In 2003,24 the surveillance of 2 small adenomas was extended from 3 years to 5 years. The guidelines from 20064 suggested that individuals who had 1 or 2 small adenomas could have surveillance after 5 to 10 years, and a 3-year interval was recommended for all other scenarios. Our data did not include clinical details about polyp size or histology; thus, in some instances, the endoscopist may have adhered to a follow-up that was closer to 10 years. Fourth, despite recommendations from health care providers, patients may have declined repeat colonoscopy.

Although Medicare claims data capture a large patient population and are believed to be accurate for measurement of procedure use, there are some potential limitations of the database. First, unlike the cancer-specific pathology data contained in SEER,11, 12 we did not have access to pathology of the polyps that were removed, including number, size, and presence of villous features. Based on preliminary studies in 2 local endoscopy units25 and surveys of practicing endoscopists,13 we hypothesized that the use of snare polypectomy was relatively specific for adenomatous polyps. However, the validity of this hypothesis in the general Medicare population has not been assessed. It is possible that a large number of small, nonprecancerous, hyperplastic polyps were removed using this technique; and, thus, lack of follow-up was deemed appropriate. Second, a subset of patients without polyps removed may have been erroneously coded as having undergone polypectomy and appropriately not followed. However, an analysis that linked Medicare claims to procedure notes reported a sensitivity and specificity >97% for snare polypectomy.26 Third, the current study was limited to Medicare beneficiaries aged ≥70 years older who were receiving benefits through fee-for-service arrangements. Thus, the generalizability of the findings to younger patients and managed care recipients is unknown. Conceivably, the frequency of polyp surveillance could have been much higher in younger patients with a greater perceived life expectancy, and members of managed care plans may have received different intensity of follow-up compared with beneficiaries in fee-for-service plans. In addition, the study was limited to residents of geographic areas served by SEER registries, but it is believed that these are representative of the general US population.12 Fourth, the study was limited to beneficiaries without a previous or future cancer diagnosis. Patients who receive ongoing follow-up for cancer may have greater contact with the health care system and more opportunity for colonoscopy referral, or alternatively, they may have a lower likelihood of referral if their malignant disease is deemed incurable. In addition, patients with high-risk adenomas on index colonoscopy who subsequently develop colon cancer also would be excluded. Thus, the sample may be biased toward patients with lower risk polyps who may not require intensive follow-up. Finally, given the large sample sizes, some of the differences that achieved statistical significance may not have been clinically relevant.

In summary, the findings of this population-based study suggest the under use of follow-up colonoscopy in patients who are at increased risk for subsequent colonic neoplasia. The findings are particularly relevant given related work that is consistent with the overuse of colonoscopy in patients without a history of neoplasia. Further patient and provider-based research is needed to elucidate the underlying reasons for this discordance with clinical practice guidelines.


This study was supported by a grant from the National Cancer Institute at the National Institutes of Health (R01 CA132862) and the National Center for Advancing Translational Sciences at the National Institutes of Health (ULITR000439).


The authors made no disclosures.