Surveillance after positive and negative colonoscopy examinations: issues, yields, and use

Case Report of Rare Type Submucosal Polyp-Angiolipofibroma of Sigmoid Colon

Most of the colonic submucosal mesenchymal polyps are benign tumors. They are formed by more than one type of mesenchymal tissue. The diagnosis of angiolipofibroma depends on the histological findings with the proliferation of vascular, fatty, and fibrous connective tissues. Majority of angiolipofibromas are arising in the kidney and have rare presentation as extra renal region. Here we report a case of 58-year-old female patient with angiolipofibroma of sigmoid colon (8.5 cm x 4 cm size) which was treated successfully with surgical resection. The clinical presentation, operative procedure, pathological features, and medical literature review are presented.

Interval colorectal cancer after colonoscopy

INTRODUCTION AND AIMS

Interval colorectal cancer (iCRC) can occur due to missed lesions or to a newly developed lesion. The present study aimed to assess the iCRC rate and its characteristics in our population and find possible explanations.

MATERIALS AND METHODS

A retrospective study was conducted on patients with colorectal cancer (CRC) diagnosed between January 2011 and January 2015 at our department. Demographics, endoscopic data, and tumor characteristics (location, histology, staging) were collected. We identified patients diagnosed with CCR who underwent colonoscopy at our department in the previous 10years and presented the disease (iCRC) before the date of their next recommended exam. The cases of iCRC were characterized and compared with other CRC cases. Possible explanations for the appearance of iCRC were analyzed.

RESULTS

A total of 266 patients presented with CRC, 61.7% were men, and mean patient age was 70.7years. We identified 10 patients with iCRC: 6 were men, and mean patient age was 71.1years. Mean time for iCRC diagnosis after index colonoscopy was 3.5±1.84years. Tumor was located in the right colon in 50% of the patients with iCRC and in 24.5% of the patients without iCRC (P=.091). More patients with iCRC had a family history of CRC (50%) than the patients with reference CRC (3.1%) (P=.000).

CONCLUSIONS

In our case series, 3.76% of all CRC were iCRC. There were no statistically significant differences between patients with or without iCRC, with the exception of family history of CRC.

Predicting the risk for colorectal cancer with personal characteristics and fecal immunochemical test

We aimed to predict colorectal cancer (CRC) based on the demographic features and clinical correlates of personal symptoms and signs from Tianjin community-based CRC screening data.A total of 891,199 residents who were aged 60 to 74 and were screened in 2012 were enrolled. The Lasso logistic regression model was used to identify the predictors for CRC. Predictive validity was assessed by the receiver operating characteristic (ROC) curve. Bootstrapping method was also performed to validate this prediction model.CRC was best predicted by a model that included age, sex, education level, occupations, diarrhea, constipation, colon mucosa and bleeding, gallbladder disease, a stressful life event, family history of CRC, and a positive fecal immunochemical test (FIT). The area under curve (AUC) for the questionnaire with a FIT was 84% (95% CI: 82%-86%), followed by 76% (95% CI: 74%-79%) for a FIT alone, and 73% (95% CI: 71%-76%) for the questionnaire alone. With 500 bootstrap replications, the estimated optimism (<0.005) shows good discrimination in validation of prediction model.A risk prediction model for CRC based on a series of symptoms and signs related to enteric diseases in combination with a FIT was developed from first round of screening. The results of the current study are useful for increasing the awareness of high-risk subjects and for individual-risk-guided invitations or strategies to achieve mass screening for CRC.

Association between the location of colon polyps at baseline and surveillance colonoscopy - A retrospective study

INTRODUCTION

Several factors are used to stratify the probability of polyp recurrence. However, there are no studies correlating the location of the initial polyps and the recurrent ones. The aim of this study was to verify whether the polyp location at the surveillance colonoscopy was correlated with the location of the previously excised polyps at the baseline colonoscopy.

METHODS

A retrospective study of patients submitted to colonoscopy with presence and excision of all polyps, followed by a surveillance colonoscopy. Polyp location was divided into proximal/distal to splenic flexure and rectum. Characteristics and recurrent rates at the same colon location were also evaluated.

RESULTS

Out of the 346 patients who underwent repeated colonoscopy, 268 (77.4%) had at least 1 polyp detected. For all the segments there was an increased risk of recurrent polyps in the same location and it was about four times higher in proximal (OR 3.5; CI 2.1-6.0) and distal colon segments (OR 3.8; CI 2.1-6.8), followed by three times higher in the rectum (OR 2.6; CI 1.5-4.6). No difference was found between the rates of recurrence at the same segment, taking into consideration the polyp morphology, size, polypectomy technique employed and histological classification.

CONCLUSION

There seems to be a significant association between polyp location at baseline and surveillance colonoscopy.

Prevalence of adenomas and sessile serrated adenomas in Chinese compared with Caucasians

BACKGROUND AND AIMS

Colonic adenomas and sessile serrated adenomas (SSA) are the most common premalignant polyps identified at colonoscopy. This study compares the prevalence of neoplastic polyps in Chinese and Caucasians in a general gastroenterology outpatient practice in Australia.

METHODS

This study included consecutive unselected colonoscopies performed for standard clinical indications by a single endoscopist (JMH). All polyps detected were measured, resected, and sent for histopathology. The prevalence of adenomas, advanced adenomas, SSA, and cancer in the Chinese and Caucasian cohorts were compared. Advanced adenomas were defined as adenomas > 10 mm, villous histology, or high-grade dysplasia.

RESULTS

The study included 346 Chinese and 654 Caucasians. There was no significant difference in the baseline characteristics including age, gender, and indications of colonoscopy, although Chinese were more likely to present with rectal bleeding (22.8% vs 15.9%, P = 0.01). The prevalence of adenomatous polyps was similar in both Caucasians (34.3%) and Chinese (35.3%). However, advanced adenomas were more significantly common in Caucasians (11.3%) compared with Chinese (4.6%) (P < 0.001). SSA was rare in Chinese (2%) but present more frequently in Caucasians (7%) (P = 0.001). Multivariate analysis showed that Caucasian ethnicity (odds ratio 2.4, 95% confidence interval 1.6-3.6) and the presence of SSA (odds ratio 4.4, 95% confidence interval 2.3-8.6) were independent predictors for the detection of an advanced adenoma.

CONCLUSIONS

The prevalence of significant colorectal lesions, including advanced adenomas, large adenomas, and SSA, were lower in Chinese compared with Caucasians. These findings may influence the guidelines for colonic cancer screening in Chinese populations.

Predictors of colorectal polyp recurrence after the first polypectomy in private practice settings: a cohort study

Background

Supplementary observational data in the community setting are required to better assess the predictors of colorectal polyp recurrence and the effectiveness of colonoscopy surveillance under real circumstances.

Aim

The goal of this study was to identify patient characteristics and polyp features at baseline colonoscopy that are associated with the recurrence of colorectal polyps (including hyperplastic polyps) among patients consulting private practice physicians.

Patients and Methods

This cohort study was conducted from March 2004 to December 2010 in 26 private gastroenterology practices (France). It included 1023 patients with a first-time diagnosis of histologically confirmed polyp removed during a diagnostic or screening colonoscopy. At enrollment, interviews were conducted to obtain data on socio-demographic variables and risk factors. Pathology reports were reviewed to abstract data on polyp features at baseline colonoscopy. Colorectal polyps diagnosed at the surveillance colonoscopy were considered as end points. The time to event was analyzed with an accelerated failure time model assuming a Weibull distribution.

Results

Among the 1023 patients with colorectal polyp at baseline, 553 underwent a surveillance colonoscopy. The mean time interval from baseline colonoscopy to first surveillance examination was 3.42 (standard deviation, 1.45) years. The recurrence rates were 50.5% and 32.9% for all polyps and adenomas, respectively. In multivariate models, the number of polyps at baseline was the only significant predictor for both polyp recurrence (hazard ratio [HR] 1.19, 95% CI 1.06 to 1.33), and adenoma recurrence (HR 1.17, 95% CI 1.03 to 1.34).

Conclusion

The efficacy of surveillance colonoscopy in community gastroenterology practice compared favorably with academic settings. This study provides further evidence that the number of initial colorectal polyps is useful for predicting the risk of polyp recurrence, even in the community setting.

Colorectal cancers not detected by screening flexible sigmoidoscopy in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

BACKGROUND AND OBJECTIVE

Diagnosis of colorectal cancer after negative findings on endoscopic evaluation raises concern about the effectiveness of endoscopic screening. We contrast screening-detected cancers with cancers not detected by screening among participants assigned to flexible sigmoidoscopy (FSG) in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to determine the reasons for the lack of detection of prevalent lesions.

DESIGN

Cancers detected within 1 year of a screening FSG with abnormal findings were classified as screening detected. All other cancers were categorized, based on cancer stage and years until detection, as either not detectable or prevalent but not detected at the time of screening.

SETTING/PATIENTS

A total of 77,447 subjects in the multicenter PLCO trial.

MAIN OUTCOME MEASUREMENTS

A total of 977 colorectal cancers were diagnosed with a mean follow-up of 11.5 years.

RESULTS

A total of 243 (24.9%) cancers were screening detected, 470 (48.1%) were not detectable at screening, and 264 (27.0%) were considered prevalent but not detected. Among prevalent nondetected lesions, 35.6% (n = 94) were attributed to problems in patient compliance (58 never screened, 34 delayed colonoscopy follow-up, and 2 inadequate bowel preparation), 43.9% (n = 116) were attributable to a limitation in the FSG procedure (97 beyond the reach of the sigmoidoscope and 19 inadequate depth of insertion on FSG), and 20.5% (n = 54) were caused by endoscopist limitation (33 missed on FSG, 21 missed at initial colonoscopy) (P < .0001). Had colonoscopy instead of FSG been used for screening, an additional 15.6% and as many as 19.0% of cancers may have been screening-detected.

LIMITATIONS

These estimates are reasonable approximations, but biological variability precludes precise determinations.

CONCLUSIONS

Prevalent nondetected cancers were more often attributable to problems with patient compliance or limitations in the FSG procedure than to missed lesions. Colonoscopy instead of FSG could have moderately increased the detection of cancer via screening.

Flexible sigmoidoscopy in the randomized prostate, lung, colorectal, and ovarian (PLCO) cancer screening trial: added yield from a second screening examination

BACKGROUND

Among randomized trials evaluating flexible sigmoidoscopy (FSG) for its effect on colorectal cancer mortality, only the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial screened its participants more than one time. We report outcomes from the PLCO screening FSG program and evaluate the increased yield produced by a second FSG.

METHODS

Participants were screened by 60-cm FSG in 10 regional screening centers at study entry and 3 or 5 years later, depending on the time of random assignment. Results from subsequent diagnostic intervention were tracked and recorded in a standardized fashion, and outcomes were compared according to sex and age. The protocol discouraged repeat FSG in persons with colorectal cancer or adenoma diagnosed after the initial FSG.

RESULTS

Of 77 447 enrollees, 67 073 (86.6%) had at least one FSG and 39 443 (50.9%) had two FSGs. Diagnostic intervention occurred in 74.9% after a positive first FSG and in 78.7% after a positive repeat FSG. The second FSG increased the screening yield by 32%: Colorectal cancer or advanced adenoma was detected in 37.8 per 1000 persons after first screening and in 49.8 per 1000 persons after all screenings. The second FSG increased the yield of cancer or advanced adenoma by 26% in women and by 34% in men. Of 223 subjects who received a diagnosis of colorectal carcinoma within 1 year of a positive FSG, 64.6% had stage I and 17.5% had stage II disease.

CONCLUSIONS

Repeat FSG increased the detection of colorectal cancer or advanced adenoma in women by one-fourth and in men by one-third. Screen-detected carcinomas were early stage (stage I or II) in greater than 80% of screened persons. Colorectal cancer mortality data from the PLCO, as the definitive endpoint, will follow in later publications.

Risk prediction models for colorectal cancer: a review

Risk prediction models are important to identify individuals at high risk of developing the disease who can then be offered individually tailored clinical management, targeted screening and interventions to reduce the burden of disease. They are also useful for research purposes when attempting to identify new risk factors for the disease. In this article, we review the risk prediction models that have been developed for colorectal cancer and appraise their applicability, strengths, and weaknesses. We also discuss the factors to be considered for future development and improvement of models for colorectal cancer risk prediction. We conclude that there is no model that sufficiently covers the known risk factors for colorectal cancer that is suitable for assessment of people from across the full range of risk and that a new comprehensive model is needed.

An alerting system improves adherence to follow-up recommendations from colonoscopy examinations

BACKGROUND & AIMS

Systems are available to ensure that results of tests are communicated to patients. However, lack of adherence to recommended follow-up evaluation increases risk for adverse health outcomes and medical or legal issues. We tested the effectiveness of a novel follow-up system for patients due for surveillance colonoscopy examinations.

METHODS

Electronic medical records from colonoscopies performed 5 years prior were reviewed to identify individuals due for a repeat surveillance colonoscopy examination. Patients were assigned to groups that received the standard of care or a newly developed follow-up system that included a letter to the primary care provider, 2 letters to the patient, and a telephone call to patients who had not yet scheduled an examination by the procedure due date. The primary end point was the percentage of patients who scheduled or completed the colonoscopy examination within 6 months of the due date. Secondary end points included detection rate for adenomas, sex- and ethnicity-specific follow-up rates, and patient satisfaction.

RESULTS

Of 2609 patient records reviewed, 830 (31.8%) were found to be due for a surveillance colonoscopy examination in the study period. At the conclusion of the study, 241 (44.7%) patients in the intervention arm had procedures scheduled or completed, compared with 66 (22.6%) in the control group (P < .0001). The follow-up system appeared particularly effective among non-white patients; patients reported general satisfaction with the reminder program.

CONCLUSIONS

A simple protocol of letters and a telephone call to patients who are due for colonoscopy examinations significantly improved adherence to endoscopic follow-up recommendations. This work provides justification for the creation of reminder systems to improve patient adherence to medical recommendations.

Estimated long-term effects of the initial 6 years of the German screening colonoscopy program

BACKGROUND

Colorectal cancer is the most common cancer in Germany. Screening colonoscopies have been offered as a primary screening tool in Germany since the end of 2002.

OBJECTIVE

To estimate the numbers of clinically manifest colorectal cancers prevented by detection and removal of advanced adenomas in the initial 6 years of the program.

DESIGN

Markov model with single-year transitions.

SETTING

German screening colonoscopy program.

PATIENTS

Participants in the screening colonoscopy program from 2003 to 2008.

INTERVENTIONS

Screening colonoscopy with the removal of advanced colorectal neoplasms.

MAIN OUTCOME MEASUREMENTS

The expected numbers of incident colorectal cancers prevented by detection and removal of advanced adenomas.

RESULTS

An estimated total number of 73,024 cases of colorectal cancer might have developed from the removed advanced adenomas and become clinically manifest between 55 and 84 years of age in the absence of screening colonoscopy. This number exceeds the number of colorectal cancers diagnosed in 2002 by 27%. Among prevented cancers, 8%, 43%, and 49% would have occurred at ages 55 to 64, 65 to 74, and 75 to 84 years (median age 74 years), respectively; 60% and 40% would have occurred among men and women, respectively; and 22%, 32%, 25%, and 20% would have occurred within 1 to 5, 6 to 10, 11 to 15, and 16 to 30 years, respectively, after colonoscopy (median 10 years).

LIMITATIONS

Diagnoses of advanced adenomas are based on records from a large number of endoscopists and pathology laboratories.

CONCLUSIONS

Despite relatively low screening participation, the German screening colonoscopy program is expected to make a major contribution to the prevention of colorectal cancer, even though most of the impact will only be seen in the longer run.

Protection from right- and left-sided colorectal neoplasms after colonoscopy: population-based study

BACKGROUND

Colonoscopy is used for early detection and prevention of colorectal cancer, but evidence on the magnitude of overall protection and protection according to anatomical site through colonoscopy performed in the community setting is sparse. We assessed whether receiving a colonoscopy in the preceding 10-year period, compared with no colonoscopy, was associated with prevalence of advanced colorectal neoplasms (defined as cancers or advanced adenomas) at various anatomical sites.

METHODS

A statewide cross-sectional study was conducted among 3287 participants in screening colonoscopy between May 1, 2005, and December 31, 2007, from the state of Saarland in Germany who were aged 55 years or older. Prevalence of advanced colorectal neoplasms was ascertained by screening colonoscopy and histopathologic examination of any polyps excised. Previous colonoscopy history was obtained by standardized questionnaire, and its association with prevalence of advanced colorectal neoplasms was estimated, after adjustment for potential confounding factors by log-binomial regression.

RESULTS

Advanced colorectal neoplasms were detected in 308 (11.4%) of the 2701 participants with no previous colonoscopy compared with 36 (6.1%) of the 586 participants who had undergone colonoscopy within the preceding 10 years. After adjustment, overall and site-specific adjusted prevalence ratios for previous colonoscopy in the previous 10-year period were as follows: overall, 0.52 (95% confidence interval [CI] = 0.37 to 0.73); cecum and ascending colon, 0.99 (95% CI = 0.50 to 1.97); hepatic flexure and transverse colon, 1.21 (95% CI = 0.60 to 2.42); right-sided colon combined (cecum to transverse colon), 1.05 (95% CI = 0.63 to 1.76); splenic flexure and descending colon, 0.36 (95% CI = 0.16 to 0.82); sigmoid colon, 0.29 (95% CI = 0.16 to 0.53); rectum, 0.07 (95% CI = 0.02 to 0.40); left colon and rectum combined (splenic flexure to rectum, referred to as left-sided elsewhere), 0.33 (95% CI = 0.21 to 0.53).

CONCLUSION

Prevalence of left-sided advanced colorectal neoplasms, but not right-sided advanced neoplasms, was strongly reduced within a 10-year period after colonoscopy, even in the community setting.

Utilization of surveillance colonoscopy in community practice

BACKGROUND & AIMS

The recommended timing of surveillance colonoscopy for individuals with adenomatous polyps is based on adenoma histology, size, and number. The burden and cost of surveillance colonoscopy are significant. The aim of this study was to examine the use of surveillance colonoscopy on a community-wide basis.

METHODS

We retrospectively queried participants in the Prostate, Lung, Colorectal, and Ovarian Cancer screening trial in 9 US communities about use of surveillance colonoscopy. Subjects whose initial colonoscopy showed advanced adenoma (AA), nonadvanced adenoma (NAA), or no adenoma (NA) findings were included. Colonoscopy examinations were confirmed by reviewing colonoscopy reports.

RESULTS

Of 3876 subjects selected for inquiry, 3627 (93.6%) responded. The cumulative probability of a surveillance colonoscopy within 5 years was 58.4% (n = 1342) in the AA group, 57.5% in those with >or=3 NAAs (n = 117), 46.7% in those with 1-2 NAAs (n = 905), and 26.5% (n = 1263) in subjects with NAs. Within 7 years, 33.2% of subjects with AAs received >or=2 surveillance examinations versus 26.9% for those with >or=3 NAAs, 18.2% for those with 1 or 2 NAAs, and 10.4% for those with NAs. Incomplete colonoscopy, family history of colorectal cancer, or interval adenomatous findings could explain only a minority of surveillance colonoscopy in low-risk subjects.

CONCLUSIONS

In community practice, there is substantial overuse of surveillance colonoscopy among low-risk subjects and underuse among subjects with AAs. Interventions to better align use of surveillance colonoscopy with risk for advanced lesions are needed.

Using the results of a baseline and a surveillance colonoscopy to predict recurrent adenomas with high-risk characteristics

BACKGROUND

Suggested intervals for postpolypectomy surveillance colonoscopy are currently based on the adenoma findings from the most recent examination.

OBJECTIVE

To determine the risk for clinically significant adenoma recurrence on the basis of the results of 2 previous colonoscopies.

DESIGN

Prospective cohort study.

SETTING

Academic and private centers in North America.

PATIENTS

Participants in an adenoma chemoprevention trial in which all participants had 1 or more adenoma found on complete colonoscopy at entry. For this analysis, only participants whose qualifying adenoma was their first were included. All participants then underwent second and third study colonoscopies at roughly 3-year intervals.

MEASUREMENTS

Proportion of patients with high-risk findings at the third study colonoscopy--either at least 1 advanced (> or = 1 cm or advanced histology) adenoma or multiple (> or = 3) adenomas.

RESULTS

Fifty-eight of 564 participants (10.3%) had high-risk findings at the third study examination. If the second examination showed high-risk findings, then results from the first examination added no significant information about the probability of high-risk findings on the third examination (18.2% for high-risk findings on the first examination vs. 20.0% for low-risk findings on the first examination; P = 0.78). If the second examination showed no adenomas, then the results from the first examination added significant information about the probability of high-risk findings on the third examination (12.3% if the first examination had high-risk findings vs. 4.9% if the first examination had low-risk findings; P = 0.015).

LIMITATION

This observational study cannot specifically examine adenoma recurrence risk at intervals suggested for patients with low-risk adenomas (for example, 5 years vs. 10 years).

CONCLUSION

Information from 2 previous examinations may help identify low-risk populations that benefit little from intense surveillance. Surveillance guidelines might be tailored in selected patients to use information from 2 previous examinations, not just the most recent one.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Utilization and yield of surveillance colonoscopy in the continued follow-up study of the polyp prevention trial

BACKGROUND AND AIMS

Prospective information on the use and yield of surveillance colonoscopy is limited. We examined the use and yield of surveillance colonoscopy among participants in the Polyp Prevention Trial (PPT) after the 4-year dietary intervention trial ended.

METHODS

We followed a cohort of 1297 participants. We calculated the cumulative probability of posttrial colonoscopy and investigated the yield and predictive factors for adenoma and advanced adenoma recurrence over a mean time of 5.9 years.

RESULTS

Seven-hundred seventy-four subjects (59.7%) had a repeat colonoscopy. Among 431 subjects with low-risk adenomas (1-2 nonadvanced adenomas) at baseline and no adenoma recurrence at the end of the PPT (lowest-risk category), 30.3% underwent a repeat colonoscopy within 4 years. Among 55 subjects who had high-risk adenomas (advanced adenoma and/or > or =3 nonadvanced adenomas) at baseline and again at the final PPT colonoscopy (highest-risk category), 41.3% had a colonoscopy within 3 years and 63.5% had an examination within 5 years. The cumulative yield of advanced adenoma through 6 years was 3.6% for the lowest-risk category, 38.9% for the highest-risk category, and ranged from 6.6% to 13.8% for intermediate-risk categories. An advanced adenoma at the final PPT colonoscopy was associated significantly with an advanced adenoma recurrence during surveillance (hazard ratio, 6.2; 95% confidence interval, 2.5-15.4).

CONCLUSIONS

Surveillance colonoscopy was overused for low-risk subjects and underused for high-risk subjects. Advanced adenoma yield corresponded with the adenoma risk category. Resource consumption can be better managed by aligning use with the risk of adenoma recurrence.

Can calcium chemoprevention of adenoma recurrence substitute or serve as an adjunct for colonoscopic surveillance?

OBJECTIVES

The aim of this study was to examine the potential cost-effectiveness of calcium chemoprevention post-polypectomy as a substitute or adjunct for surveillance.

METHODS

We constructed a Markov model of post-polypectomy adenoma recurrence and colorectal cancer (CRC) development, calibrated to data from prospective chemoprevention trials of fiber, calcium, antioxidants, and aspirin. We modeled four scenarios for 50-year-old patients immediately after polypectomy: (i) natural history with no further intervention; (ii) elemental calcium 1,200 mg/day from age 50-80; (iii) surveillance colonoscopy from age 50-80 every 5 years, or 3 years for large adenoma; (iv) calcium + surveillance. Patients were followed up until age 100 or death.

RESULTS

Calcium was cost-effective compared to natural history ($49,900/life-year gained). However, surveillance was significantly more effective than calcium (18.729 versus 18.654 life-years/patient; 76 percent versus 14 percent reduction in CRC incidence) at an incremental cost of $15,900/life-year gained. Calcium + surveillance yielded a very small benefit (0.0003 incremental life-years/patient) compared with surveillance alone, at a substantial incremental cost of $3,090,000/life-year gained.

CONCLUSION

Post-polypectomy calcium chemoprevention is unlikely to be a reasonable substitute for surveillance. It may be cost-effective in patients unwilling or unable to undergo surveillance.

High detection rates of colorectal neoplasia by stool DNA testing with a novel digital melt curve assay

BACKGROUND & AIMS

Current stool DNA tests identify about half of individuals with colorectal cancers and miss most individuals with advanced adenomas. We developed a digital melt curve (DMC) assay to quantify low-abundance mutations in stool samples for detection of colorectal neoplasms and compared this test with other approaches.

METHODS

We combined a melt curve assay with digital polymerase chain reaction and validated the quantitative range. We then evaluated its ability to detect neoplasms in 2 clinical studies. In study I, stool samples from patients with colorectal tumors with known mutations (KRAS, APC, BRAF, TP53) were assayed. In study II, archived stool samples from patients with advanced adenomas containing known KRAS mutations were assayed, along with controls. Results were compared with those from the stool DNA test PreGenPlus (Exact Sciences, Marlborough, MA), Hemoccult, and HemoccultSensa (both Beckman-Coulter, Fullerton, CA).

RESULTS

The DMC assay detected samples in which only 0.1% of target genes were mutated. In study I, the DMC assay detected known mutations in 28 (90%) of 31 tumor samples and 6 (75%) of 8 advanced adenoma samples. In study II, the DMC assay detected 16 (59%) of 27 advanced adenoma samples that contained KRAS mutations, compared with 7% with the Hemoccult, 15% with the HemoccultSensa, and 26% with the PreGenPlus assays (P < .05 for each, compared with the DMC assay); specificities did not differ significantly.

CONCLUSIONS

The DMC assay has a high level of sensitivity in detecting individuals with colon neoplasms and is better than current stool screening methods in detecting those with advanced adenomas. Further studies are indicated.

The yield of surveillance colonoscopy by adenoma history and time to examination

BACKGROUND & AIMS

Surveillance colonoscopy is recommended for subjects with a history of adenomas but there is limited information on the yield of surveillance.

METHODS

A sample of subjects in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial with abnormal flexible sigmoidoscopy and follow-up colonoscopy were queried about subsequent surveillance colonoscopy over a 10-year period. Medical records were obtained to verify procedure dates and histologic findings. Subjects with advanced adenomas, nonadvanced adenoma, nonadenomatous polyps, and no polyps at baseline were included.

RESULTS

At the first surveillance, 10.5% had advanced adenoma and 37% had any adenoma in the advanced adenoma group (n = 1057), compared with rates of 6.8% and 32% (nonadvanced adenoma: n = 765), 4.9% and 22% (nonadenomatous polyps: n = 658), and 3.1% and 16% (no polyps: n = 127) (P < .0001, linear trend test). Mean (SD) time intervals (years) from baseline colonoscopy to first surveillance were 3.4 (2.0) for advanced adenoma, 4.3 (2.0) for nonadvanced adenoma, 4.5 (2.0) for nonadenomatous polyps, and 4.7 (2.0) for no polyps. There were no increasing (or decreasing) trends in the observed rate of advanced adenoma or any adenoma with time to the initial surveillance examination in any baseline group. Among subjects with a second surveillance examination, adenoma findings at both baseline and first surveillance influenced the rates of advanced adenoma and any adenoma at second surveillance.

CONCLUSIONS

Subjects with baseline advanced adenomas are more likely to have recurrent advanced adenomas at initial surveillance. The lack of association between recurrence rates and time to surveillance suggests limitations in our understanding of the biology of adenoma development.

Yield of advanced adenoma and cancer based on polyp size detected at screening flexible sigmoidoscopy

BACKGROUND & AIMS

Observational screening of the colon with subsequent referral for colonoscopy raises questions about the threshold of polyp size that necessitates referral. To examine the yield at colonoscopy when a given size lesion is observed, we assessed the yield of advanced adenoma and cancer at colonoscopy based on the size of the abnormality detected at flexible sigmoidoscopy (FSG).

METHODS

We used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a randomized, controlled, community-based study of FSG.

RESULTS

Subsequent colonoscopy was performed on 10,850 subjects (60.4% male; mean age, 62.9 years) with a polyp visualized on screening FSG. For women with a polyp 0.5-0.9 cm on FSG (n = 1426), the yield in the distal colon on colonoscopy was 0.6% for cancer (number needed to screen [NNS] = 166) and 14.5% for advanced adenoma (NNS = 7). In men (n = 2183), the yield was 0.7% (NNS = 142) for cancer and 15.9% (NNS = 6) for advanced adenoma. Among persons with polyps 0.5-0.9 cm identified on FSG, 5.5% (198/3609) had distal advanced adenomas that measured <1.0 cm but had villous histology or high-grade dysplasia, and 9.9% (357/3609) had adenomas > or =1 cm.

CONCLUSIONS

The yield for a distal advanced adenomatous lesion when a polyp 0.5-0.9 cm is observed at FSG is substantial and is due to the presence of advanced histology in polyps <1 cm and to detection of polyps that measure > or =1.0 cm on colonoscopy. Establishing thresholds for observation versus evaluation will require careful assessment of the overall yield.

Repeat colonoscopy has a low yield even in symptomatic patients

BACKGROUND

In many regions, the demand for colonoscopy exceeds its availability. Patients undergoing repeat examinations comprise a significant proportion of those on waiting lists.

OBJECTIVE

To assess the yield of repeat colonoscopy in varied clinical settings.

DESIGN

Cohort study.

SETTING

Endoscopic database of an Australian tertiary referral hospital.

PATIENTS

Adults who had >/=2 colonoscopies between 1992 and 2004. Patients were excluded if the repeat procedure was for completion or for high-risk surveillance.

MAIN OUTCOME MEASUREMENTS

Yield for neoplasia by indication, interval to repeat examination, and appropriateness for surveillance (determined by National Australian guidelines).

RESULTS

A total of 4974 colonoscopies in 2075 patients were studied. The mean age was 63.1 years (range, 19.2-92.4 years). The mean number of examinations was 2.4 (range, 2-8), with a mean interval between examinations of 2.9 years. Colorectal cancer (CRC) was significantly more prevalent at initial colonoscopy compared with subsequent colonoscopies (7.9% vs 0.6%; prevalence ratio 14.2, 95% confidence interval [CI] 8.5-23.7, P < .001), as were advanced adenomas (15.3% vs 4.8%; prevalence ratio 3.2, 95% CI 2.6-3.9, P < .001). No CRCs were detected in symptomatic patients undergoing polyp surveillance examinations performed before the recommended interval.

LIMITATIONS

Retrospective design.

CONCLUSIONS

Yield of repeat colonoscopy is significantly lower than for initial colonoscopy, irrespective of indication. In symptomatic patients within a polyp surveillance program, the yield is negligible when a colonoscopy is performed before the recommended surveillance interval. The need for a repeat colonoscopy should be carefully considered, and patients who have never had a colonoscopy must take priority on waiting lists over those awaiting repeat examinations.

Cigarette smoking, N-acetyltransferase genes and the risk of advanced colorectal adenoma

Background: Cigarette use is associated with greater risk for colorectal adenoma, a colorectal cancer precursor. N-acetyltransferases, NAT1 and NAT2, are important enzymes involved in the metabolism of aromatic amine carcinogens present in cigarette smoke. Our interest is in the polymorphisms within the NAT1 and NAT2 genes that influence the tobacco–colorectal tumor relationship by impacting on the metabolic activation and detoxification of tobacco smoke-derived carcinogens. Methods: In the Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trial, we compared NAT1 and NAT2 gene variant distributions for 772 cases with left-sided advanced adenoma and 777 gender and age-matched controls. Individual NAT1 and NAT2 diplotypes were assigned and NAT2 acetylator phenotypes were derived. Results: Risks for advanced colorectal adenoma were significantly increased among recent smokers (current smokers or those who quit less than 10 years ago) (odds ratio [OR] = 2.3, 95% confidence interval [CI]: 1.7–3.1) and among those who smoked more than 20 cigarettes per day (OR = 1.7, 95% CI: 1.3–2.2), compared with nonsmokers. Risk decreased with increasing NAT2 phenotypic activity (0: slow, 1: intermediate, and 2: rapid) (OR trend: 0.8; 95% CI: 0.7–1.0, p-trend = 0.04) overall. When stratified by smoking status, significant phenotype-associated trends were observed among recent smokers (OR trend = 0.4, 95% CI: 0.3–0.7, p trend <0.001) (p-interaction = 0.02), but not among past or nonsmokers. Diplotypes most strongly associated with lower risks in smokers were NAT2*4/*5B (OR = 0.3, 95% CI: 0.1–0.8, p = 0.01) and NAT2*4/*4 (OR = 0.2, 95% CI: 0.04–0.7, p = 0.02), categorized as intermediate and rapid acetylators, respectively. One NAT1 diplotype, NAT1*4/*10 (OR = 0.5, 95% CI: 0.3–0.9, p = 0.03), was also associated with a decreased risk in smokers. Conclusions: Our study indicated that NAT2 gene variants associated with a slow acetylator phenotype were more susceptible to the effects of tobacco smoking with respect to adenoma risk, providing leads for disease prevention.

Visceral fat analysis at CT colonography

RATIONALE AND OBJECTIVES

Obesity is associated with increased risks for colorectal neoplasia. Few studies have examined quantitative body fat measurements as predictors of colorectal polyps. The objective is to determine whether visceral fat is associated with colorectal polyps at computed tomography (CT) colonography.

MATERIALS AND METHODS

Case (n = 25) and control (n = 25) subjects with proven large (>1 cm) colorectal adenomas or normal colons respectively were randomly selected from among an established CT colonography research study cohort. Using supine CT colonography data, the body wall was traced at three levels: top of the right kidney, iliac crest, and superior acetabulum. Total area from the three slices and each slice area were determined within the visceral fat range (-170 to -45 Hounsfield units) and recorded within the selected region. Visceral fat measures were compared between patient groups with and without polyps.

RESULTS

None of the single slice visceral fat area measures or summed measures predicted case or control status. The most informative visceral fat measure was obtained at the top of the right kidney with a maximum area under the received operator characteristic curve of 0.77 (0.05 SE). For a selected sensitivity of 75%, the maximum specificity for a large (>or=1 cm) polyp was 64%.

CONCLUSION

In this pilot study, visceral fat measures at CT colonography were not significantly associated with the presence of large colorectal adenomas. However, odd ratios were elevated by a factor of 2. This suggests that a larger study may be justified.

Colorectal cancer screening: today and tomorrow

Colorectal cancer remains a disease with significant morbidity and mortality. However, the prognosis can be greatly improved with early detection. Here, we review the current screening modalities and guidelines for patients at average, moderate, and high risk for colorectal cancer. New experimental modalities are also introduced.

Projected national impact of colorectal cancer screening on clinical and economic outcomes and health services demand

BACKGROUND & AIMS

Colorectal cancer (CRC) screening is effective and cost-effective, but the potential national impact of widespread screening is uncertain. It is controversial whether screening colonoscopy can be offered widely and how emerging tests may impact health services demand. Our aim was to produce integrated, comprehensive estimates of the impact of widespread screening on national clinical and economic outcomes and health services demand.

METHODS

We used a Markov model and census data to estimate the national consequences of screening 75% of the US population with conventional and emerging strategies.

RESULTS

Screening decreased CRC incidence by 17%-54% to as few as 66,000 cases per year and CRC mortality by 28%-60% to as few as 23,000 deaths per year. With no screening, total annual national CRC-related expenditures were 8.4 US billion dollars. With screening, expenditures for CRC care decreased by 1.5-4.4 US billion dollars but total expenditures increased to 9.2-15.4 US billion dollars. Screening colonoscopy every 10 years required 8.1 million colonoscopies per year including surveillance, with other strategies requiring 17%-58% as many colonoscopies. With improved screening uptake, total colonoscopy demand increased in general, even assuming substantial use of virtual colonoscopy.

CONCLUSIONS

Despite savings in CRC care, widespread screening is unlikely to be cost saving and may increase national expenditures by 0.8-2.8 US billion dollars per year with conventional tests. The current national endoscopic capacity, as recently estimated, may be adequate to support widespread use of screening colonoscopy in the steady state. The impact of emerging tests on colonoscopy demand will depend on the extent to which they replace screening colonoscopy or increase screening uptake in the population.

Analysis of colorectal cancer occurrence during surveillance colonoscopy in the dietary Polyp Prevention Trial

BACKGROUND

Interval colorectal cancer (CRC) occasionally is detected in patients who have recently undergone colonoscopy. Systematic evaluation of CRC detected after colonoscopy could identify ways to improve the quality and the outcome of colonoscopy.

METHODS

This study examined cancer diagnoses in the course of the dietary Polyp Prevention Trial, a randomized study of a dietary intervention on recurrence of adenomatous polyps. An algorithm was developed to classify each cancer into one of 4 etiologies: (1) incomplete removal (cancer at the site of previous adenoma), (2) failed biopsy detection (cancer in an area of suspected neoplasia with negative biopsy specimens), (3) missed cancer (large, advanced stage cancer found at a short interval after colonoscopy), or (4) new cancer (small, early stage cancer after a longer time interval).

RESULTS

Of 2079 patients, 13 had cancer detected over 5810 person years of observation (PYO) (2.2 cases/1000 PYO); 7/13 or 53.8% of patients had either a potentially "avoidable" cancer or one detectable at an earlier time interval because of incomplete removal (4/13) or missed cancer (3/13).

CONCLUSIONS

Interval cancer occurs despite colonoscopy. Improved quality of colonoscopy may have reduced cancer prevalence or resulted in earlier cancer detection in over 50% of prevalent cancers in the dietary Polyp Prevention Trial.

The Effect of Diagnostic Confidence on the Probability of Optical Colonoscopic Confirmation of Potential Polyps Detected on CT Colonography:Prospective Assessment in 1,339 Asymptomatic Adults

OBJECTIVE

We sought to evaluate the effect of interpreter confidence on the likelihood that a lesion detected on CT colonography (CTC) will correspond to a matched polyp seen on optical colonoscopy.

SUBJECTS AND METHODS

Same-day CTC and optical colonoscopy were performed on 1,339 asymptomatic adults. A standard matching algorithm for polyp size and location was used. For each potential polyp detected on CTC, the level of diagnostic confidence was prospectively rated on a 3-point scale (1, least certain; 2, intermediate; and 3, most certain).

RESULTS

For CTC-detected lesions 6 mm or larger, diagnostic confidence levels of 1, 2, and 3 corresponded to matched polyps on optical colonoscopy in 33.3% (45/135), 50.0% (103/206), and 66.8% (157/235) of cases, respectively (p < 0.01). Similar trends were present for categories of lesions that measured 6-7 mm, 8-9 mm, and 10 mm or larger, rising to a match rate of 82.1% (55/67) for lesions 10 mm or larger that were diagnosed with a level-3 confidence rating. The likelihood that a matched polyp was adenomatous increased with greater levels of diagnostic confidence. Of note, level-3 confidence for lesions measuring 8-9 mm on CTC more often yielded a matching neoplasm on optical colonoscopy than level-1 or level-2 confidence for lesions measuring 10 mm or larger (60.3% [35/58] vs 20.8% [10/48]; p < 0.0001).

CONCLUSION

Greater diagnostic confidence for an individual lesion detected on CTC correlates with a significantly increased likelihood that a matching polyp will be found on optical colonoscopy and that this matched polyp will be neoplastic. Although polyp size represents the primary criterion for CTC screening algorithms, this data could help guide the decision to opt for noninvasive CTC surveillance versus optical colonoscopy for polypectomy.

Relationship of visceral adipose tissue to recurrence of adenomatous polyps

OBJECTIVES

Insulin is a growth factor for colorectal cancer. Visceral adipose tissue (VAT) is strongly associated with insulin levels, and insulin and visceral obesity have been associated in cohort studies with colorectal cancer. The aim of this investigation was to determine whether VAT is associated with recurrence of adenomatous polyps, the precursor to colorectal cancer.

METHODS

As an ancillary study to the Polyp Prevention Trial, a randomized clinical trial that evaluated the effect of a low-fat, high-fiber, high vegetable and fruit diet on adenomatous polyp recurrence, subjects at one clinical center underwent measurement of VAT with a single-slice CT scan through the L4-L5 interspace. The scan was performed around the time of the subject's year 4 colonoscopy that determined adenoma recurrence.

RESULTS

Of 119 subjects, 44 of 84 men (52%) and 16 of 35 women (46%) had a recurrent adenoma (p= 0.51). Body mass index (BMI) and weight at baseline and at year 4 colonoscopy were unrelated to adenoma recurrence. In a multivariate model including visceral fat quartile, remote history of polyps, gender, age, and randomization group, only remote history of polyps was statistically significantly associated with recurrent adenoma with a relative risk of 4.6 (95% CI 1.7, 12.4, p= 0.001). There was no consistent monotonic trend of increased or decreased risk of recurrence as one ascended quartiles of adipose tissue for visceral, subcutaneous, or total abdominal fat.

CONCLUSION

In this study, no association between visceral adipose tissue and adenomatous polyp recurrence was observed. Further study and exploration of the role of VAT in adenoma progression is required.