Does colonoscopic polypectomy reduce the incidence of colorectal carcinoma?

Should Assessment of Quality Indicator of Colonoscopy Be Varied Depending on the Colonoscopic Technique Level?

BACKGROUND/AIM

The purpose of this research was to evaluate if withdrawal time is a useful index in spite of differences in gastroenterologists' ability and if there are other quality indicators of colonoscopy.

METHODS

A total of 665 consecutive, asymptomatic individuals of average risk between 50 and 75 years of age who underwent screening colonoscopies performed by 12 gastroenterologists were included in this study. The endoscopists were classified to either the experienced group (group A, N = 6) or the under-experienced group (group B, N = 6). The endoscopists were unaware that they were being studied during the two-month study period.

RESULTS

In group A, adenoma detection rate was 0.56, while in group B it was 0.43 (P = 0.048). The mean withdrawal time ranged widely from 4.2 to 10.3 min per patient with a mean value of 6.83 for group A and 6.54 for group B. There was a significantly positive relationship between the number of adenomas detected and the withdrawal time for group B (r = 0.827, P = 0.005), but not for group A (r = -0.152, P = 0.584). In the case of group A, the ratio of cecal intubation time to withdrawal time (I/E ratio) less than 1 showed significantly correlated adenoma detection rate compared to I/E ratio greater than 1 (r = -0.308, P = 0.036). In the case of group B, mean I/E ratio was 1.7 and all endoscopists' I/E ratios were greater than 1.

CONCLUSIONS

For experienced endoscopists, a useful supplementary quality indicator of colonoscopy is to keep intubation/withdrawal time ratio less than 1 and it is necessary for under-experienced endoscopists to try to keep enough withdrawal time.

Comparing the effectiveness of competing tests for reducing colorectal cancer mortality: a network meta-analysis

BACKGROUND

Comparative effectiveness data pertaining to competing colorectal cancer (CRC) screening tests do not exist but are necessary to guide clinical decision making and policy.

OBJECTIVE

To perform a comparative synthesis of clinical outcomes studies evaluating the effects of competing tests on CRC-related mortality.

DESIGN

Traditional and network meta-analyses. Two reviewers identified studies evaluating the effect of guaiac-based fecal occult blood testing (gFOBT), flexible sigmoidoscopy (FS), or colonoscopy on CRC-related mortality.

INTERVENTIONS

gFOBT, FS, colonoscopy.

MAIN OUTCOME MEASUREMENTS

Traditional meta-analysis was performed to produce pooled estimates of the effect of each modality on CRC mortality. Bayesian network meta-analysis (NMA) was performed to indirectly compare the effectiveness of screening modalities. Multiple sensitivity analyses were performed.

RESULTS

Traditional meta-analysis revealed that, compared with no intervention, colonoscopy reduced CRC-related mortality by 57% (relative risk [RR] 0.43; 95% confidence interval [CI], 0.33-0.58), whereas FS reduced CRC-related mortality by 40% (RR 0.60; 95% CI, 0.45-0.78), and gFOBT reduced CRC-related mortality by 18% (RR 0.82; 95% CI, 0.76-0.88). NMA demonstrated nonsignificant trends favoring colonoscopy over FS (RR 0.71; 95% CI, 0.45-1.11) and FS over gFOBT (RR 0.74; 95% CI, 0.51-1.09) for reducing CRC-related deaths. NMA-based simulations, however, revealed that colonoscopy has a 94% probability of being the most effective test for reducing CRC mortality and a 99% probability of being most effective when the analysis is restricted to screening studies.

LIMITATIONS

Randomized trials and observational studies were combined within the same analysis.

CONCLUSION

Clinical outcomes studies demonstrate that gFOBT, FS, and colonoscopy are all effective in reducing CRC-related mortality. Network meta-analysis suggests that colonoscopy is the most effective test.

Colorectal cancers soon after colonoscopy: a pooled multicohort analysis

OBJECTIVE

Some individuals are diagnosed with colorectal cancer (CRC) despite recent colonoscopy. We examined individuals under colonoscopic surveillance for colonic adenomas to assess possible reasons for diagnosing cancer after a recent colonoscopy with complete removal of any identified polyps.

DESIGN

Primary data were pooled from eight large (>800 patients) North American studies in which participants with adenoma(s) had a baseline colonoscopy (with intent to remove all visualised lesions) and were followed with subsequent colonoscopy. We used an algorithm based on the time from previous colonoscopy and the presence, size and histology of adenomas detected at prior exam to assign interval cancers as likely being new, missed, incompletely resected (while previously an adenoma) or due to failed biopsy detection.

RESULTS

9167 participants (mean age 62) were included in the analyses, with a median follow-up of 47.2 months. Invasive cancer was diagnosed in 58 patients (0.6%) during follow-up (1.71 per 1000 person-years follow-up). Most cancers (78%) were early stage (I or II); however, 9 (16%) resulted in death from CRC. We classified 30 cancers (52%) as probable missed lesions, 11 (19%) as possibly related to incomplete resection of an earlier, non-invasive lesion and 14 (24%) as probable new lesions. The cancer diagnosis may have been delayed in three cases (5%) because of failed biopsy detection.

CONCLUSIONS

Despite recent colonoscopy with intent to remove all neoplasia, CRC will occasionally be diagnosed. These cancers primarily seem to represent lesions that were missed or incompletely removed at the prior colonoscopy and might be avoided by increased emphasis on identifying and completely removing all neoplastic lesions at colonoscopy.

Korean guidelines for postpolypectomy colonoscopy surveillance

Postpolypectomy surveillance has become a major indication for colonoscopy as a result of increased use of screening colonoscopy in Korea. In this report, a careful analytic approach was used to address all available evidences to delineate the predictors for advanced neoplasia at surveillance colonoscopy and we elucidated the high risk findings of the index colonoscopy as follows: 3 or more adenomas, any adenoma larger than 10 mm, any tubulovillous or villous adenoma, any adenoma with high-grade dysplasia, and any serrated polyps larger than 10 mm. Surveillance colonoscopy should be performed five years after the index colonoscopy for those without any high-risk findings and three years after the index colonoscopy for those with one or more high risk findings. However, the surveillance interval can be shortened considering the quality of the index colonoscopy, the completeness of polypectomy, the patient's general condition, and family and medical history.

Colorectal cancers detected after colonoscopy frequently result from missed lesions

BACKGROUND & AIMS

Colorectal cancers (CRCs) that are detected in patients who have received colonoscopies (interval cancers) arise from missed lesions, incomplete resections of adenomas, or de novo. We estimated rates of interval cancer from missed lesions.

METHODS

Adenoma miss rates, cancer prevalence among patients with adenoma (based on size), and rates of adenoma-to-cancer transitions were estimated from the literature. We used a model to apply these risk estimates to a hypothetical average-risk population that received screening colonoscopies. We calculated the proportion of individuals with tumors missed at the baseline colonoscopy and tumors that arose from missed adenomas during a 5-year follow-up period. Sensitivity analyses were performed to assess robustness.

RESULTS

We found that 0.7 per 1000 persons undergoing a screening colonoscopy had a cancer that was missed at the baseline colonoscopy and an additional 1.1 per 1000 subsequently developed cancer from a missed adenoma. Therefore, the expected rate of individuals with CRC, based on missed adenomas, was 1.8 per 1000 persons within 5 years. By using the most conservative assumptions-a low miss rate and low prevalence of cancer in adenomas-0.5 per 1000 persons would have a detectable CRC within 5 years after a screening colonoscopy. In contrast, using the highest reported miss rates and cancer prevalence, CRCs from missed lesions would occur in 3.5 per 1000 screened persons.

CONCLUSIONS

A significant number of patients undergoing a screening colonoscopy that did not detect cancer actually have a malignant lesion or adenoma that could progress in a short interval. Most interval cancers might reflect missed rather than new lesions. Improving adenoma detection could reduce the rate of interval cancers.

[Colorectal cancer: from diagnosis to screening]

Colorectal cancer fulfils the conditions required for mass screening. Data from controlled studies indicate that it is possible to reduce colorectal cancer mortality at a population level using faecal occult blood testing. Screenings rely on biennial testing in between 50 and 74average risk subjects. Compliance must be over 50%. Colorectal cancer mortality decrease in this case between 15 and 18% in the general population, 33 and 39% among participants to screening. The European Commission, on the basis of available data recommended to organise colorectal cancer screening in the European Union. Generalisation of screening has become a reality in France. Epidemiological studies allow us to define subjects at very high risk (genetic origin) and high risk for colorectal cancer. Colonoscopy screening is recommended in first degree relatives of patients with colorectal cancer or large adenoma diagnosed before 60years or with two affected first-degree relatives, in subjects with an extended inflammatory bowel disease, or with a personal history of large bowel cancer or large adenoma. Promising research strategies are arising: immunochemical tests in the short term, stool-based DNA tests in stools and proteome-based approach in the long term.

Influence of long-term colonoscopic surveillance on incidence of colorectal cancer and death from the disease in patients with precursors (adenomas)

Case-control studies and short term prospective studies have suggested that selected groups of patients with precursors of colorectal cancer may benefit from colonoscopic surveillance after initial removal of adenomas. The aim of the present study was to demonstrate such a possible benefit from long term (1-24 years) colonoscopic surveillance in a population of patients with all types of adenomas regardless of size and way of removal. Two thousand and forty-one patients with a first time diagnosis of colorectal adenoma were included in prospective surveillance between year 1978 and 2002. All adenomas were considered. Incidence of CRC and mortality from CRC was calculated, using age, sex, and calendar specific number of person years of follow-up for comparison with the standard Danish population. CRC was found in 27 patients, the expected number being 41 (RR 0.65, 95% CI 0.43-0.95). Three of the 27 patients died from CRC, the expected number being 25 (RR 0.12, 95% CI 0.03-0.36). A total of 6 289 colonoscopies resulted in severe complications in 20 patients and two died from complications. Long-term colonoscopic surveillance may reduce incidence of CRC as well as mortality in patients with sporadic adenomas. The benefit is reduced to a minor degree by complications from surveillance.

Chromoendoscopy detects more adenomas than colonoscopy using intensive inspection without dye spraying

Conventional colonoscopy misses some neoplastic lesions. We compared the sensitivity of chromoendoscopy and colonoscopy with intensive inspection for detecting adenomatous polyps missed by conventional colonoscopy. Fifty subjects with a history of colorectal cancer or adenomas underwent tandem colonoscopies at one of five centers of the Great Lakes New England Clinical Epidemiology and Validation Center of the Early Detection Research Network. The first exam was a conventional colonoscopy with removal of all visualized polyps. The second exam was randomly assigned as either pan-colonic indigocarmine chromoendoscopy or standard colonoscopy with intensive inspection lasting >20 minutes. Size, histology, and numbers of polyps detected on each exam were recorded. Twenty-seven subjects were randomized to a second exam with chromoendoscopy and 23 underwent intensive inspection. Forty adenomas were identified on the first standard colonoscopies. The second colonoscopies detected 24 additional adenomas: 19 were found using chromoendoscopy and 5 were found using intensive inspection. Chromoendoscopy found additional adenomas in more subjects than did intensive inspection (44% versus 17%) and identified significantly more missed adenomas per subject (0.7 versus 0.2, P < 0.01). Adenomas detected with chromoendoscopy were significantly smaller (mean size 2.66 +/- 0.97 mm) and were more often right-sided. Chromoendoscopy was associated with more normal tissue biopsies and longer procedure times than intensive inspection. After controlling for procedure time, chromoendoscopy detected more adenomas and hyperplastic polyps compared with colonoscopy using intensive inspection alone. Chromoendoscopy detected more polyps missed by standard colonoscopy than did intensive inspection. The clinical significance of these small missed lesions warrants further study.

A deterministic model for estimating the reduction in colorectal cancer incidence due to endoscopic surveillance

There is evidence that the removal of adenomas, by endoscopy, from the large bowel can prevent the occurrence of colorectal cancer (CRC). However, the reduction in cancer incidence due to endoscopic surveillance is difficult to estimate. Studies of cohorts of adenoma patients typically rely on comparisons with groups of historical controls. We present a model for disease progression which enables estimation of this quantity without direct comparison to a reference group. Models are applied to data from the National Polyp Study. Rates of adenoma recurrence and progression to carcinoma are estimated based on study data and relevant literature. This allows calculation of the number of cancers expected in the absence of surveillance and, thus, the number of cancers prevented. Results are compared with the original analysis. Models estimate that surveillance reduced CRC incidence by at least 97% in this cohort. The majority of the effect was due to the initial removal of adenomas rather than the follow-up surveillance. These results are similar to those produced in the original analysis when using the most appropriate reference groups. They indicate that polypectomy and follow-up surveillance can lead to large reductions in cancer incidence which may have been under-estimated in previous studies.

Colorectal cancer risk after colonoscopic polypectomy: a population-based study and literature search

Adenoma patients are considered to be at an elevated risk for colorectal cancer, even after their adenomas have been removed. The aim of this study was to estimate the colorectal cancer risk after colonoscopic polypectomy compared with age- and gender-matched general population controls. Colorectal cancer incidence was studied in 553 consecutive patients without cancer whose adenomas were colonoscopically removed in the endoscopy department of a general hospital. The colorectal cancer relative risk in these patients was 0.9 (0.3-2.0). A literature search was performed to identify all published studies on relative colorectal cancer risk after polypectomy. The relative risk estimates in seven other studies ranged from 0.2 (0.1-0.6) to 1.3 (0.6-2.3). The difference can, be explained partially by the inclusion or exclusion of patients with large sessile polyps and other factors. Our review shows that colorectal cancer risk after colonoscopic polypectomy does not exceed the risk in the general population.

Colorectal cancer screening at a Veterans Affairs hospital

BACKGROUND

Because of limited resources and common barriers to widespread screening, the Surgery Service of the Indianapolis Veterans Affairs Medical Center has focused its colorectal screening program on patients undergoing hernia repair. Our objective was to examine the success, safety, pathology results, and educational benefit of this nontraditional screening program.

METHODS

The study was a retrospective analysis of a prospectively collected database (1991 to 2002). Initial screening colonoscopy was performed on 263 average-risk Veterans Affairs patients, 217 (83%) in conjunction with hernia repair. Visualized polyps were removed or biopsied during colonoscopy and pathology reports for all specimens were examined. Results were compared with published screening studies.

RESULTS

Complete colonoscopy, defined as cecal intubation, was performed in 93% of initial screening colonoscopies. There were no major complications, including perforation, excessive bleeding, or death, from colonoscopy. Initial colonoscopy showed adenomas in 67 patients (25%), hyperplastic polyps in 34 (13%), and invasive cancer in 4 (1.5%). Follow-up endoscopies revealed cancer in 2 additional patients, 3 and 5 years after initial screening.

CONCLUSIONS

This program is an important training resource for surgical residents. Screening colonoscopy performed in conjunction with hernia repair has produced results consistent with more conventional methods. The Surgery Service at the Indianapolis Veterans Affairs Medical Center is providing colorectal cancer screening with a high degree of safety and success in the face of limited resources and common barriers to implementation of widespread screening.

Cost-utility of one-time colonoscopic screening for colorectal cancer at various ages

OBJECTIVE

One-time colonoscopy has been recommended as a possible colorectal cancer (CRC) screening strategy. Because the incidence of colorectal neoplasia increases with age, the effectiveness and cost of this strategy depend on the age at which screening occurs. The purpose of this study was to investigate the age-dependent cost-utility of one-time colonoscopic screening.

METHODS

We constructed a computer simulation model of the natural history of colorectal neoplasia. This model was used to compare the cost-utility of no screening and age-based strategies employing one-time colonoscopic screening (age ranges evaluated: 45-49, 50-54, 55-59, and 60-64 yr).

RESULTS

We determined that one-time colonoscopic screening in men age <60 yr and in women age <65 yr dominates never screening and screening at older ages. For both sexes, one-time colonoscopic screening between 50 and 54 yr of age is associated with a marginal cost-utility of less than $10,000 per additional quality-adjusted life-year compared to screening between 55 and 60 yr of age. One-time colonoscopic screening between 45 and 49 yr of age is either dominated (women) or associated with a marginal cost-utility of $69,000/per quality-adjusted life-year (men) compared to screening between 50 and 54 yr of age. The marginal cost-utility of one-time colonoscopic screening is relatively insensitive to plausible changes in the cost of colonoscopy, the cost of CRC treatment, the sensitivity of colonoscopy for colorectal neoplasia, the utility values representing the morbidity associated with the CRC-related health states, and the discount rate.

CONCLUSIONS

One-time colonoscopic screening between 50 and 54 yr of age is cost-effective compared to no screening and screening at older ages in both men and women. Screening in men between 45 and 49 yr of age may be cost-effective compared to screening between 50 and 54 yr of age depending on societal willingness to pay.

Community screening for colorectal cancer in north-eastern New South Wales, 1987-1996

OBJECTIVE

To analyse results of Bowelscan, a community-based colorectal cancer screening program using Hemoccult II, and targeting people aged 40 years and over.

DESIGN

Survey of data from medical practitioners on follow-up of positive tests.

SETTING

North-eastern New South Wales (Rotary District 9650), 1987-1996.

SUBJECTS

3845 people with positive results for faecal occult blood.

OUTCOME MEASURES

Investigations performed; final diagnoses; number, site and Dukes' stage of colorectal carcinomas; number and histological diagnosis of colorectal polyps.

RESULTS

239,500 Hemoccult II kits were distributed between 1987 and 1996, with an estimated return rate of 80%-85%. Positive results for faecal occult blood were reported for 3845 tests (1.6% of those distributed), with 78% of these investigated by colonoscopy and/or barium enema. Investigation resulted in diagnosis of 260 colorectal carcinomas in 252 people (6.7%); 74 of these (29%) were in the caecum or ascending or transverse colon. Dukes' tumour stages were: A, 107 (41%); B, 86 (33%); C, 49 (19%); D, 16 (6%); and unknown, 2 (0.8%). (Corresponding figures from the NSW Central Cancer Registry were: A and B, 48%; C, 26%; D, 14% and unknown 12%) [corrected]. Colorectal polyps were found in a further 819 people (21.3%), and were adenomatous in 577 (79% of the 733 in whom histological diagnosis was available). Other gastrointestinal conditions were found in 1343 people (34.9%), while no cause was found for the positive result, despite adequate investigation, in 873 (22.7%).

CONCLUSION

Community-based screening with faecal occult blood testing detected colorectal carcinomas at earlier histological stages than colorectal carcinomas reported to the Cancer Registry and should reduce mortality from this disease. Treatment and follow-up of adenomatous polyps detected by such a program might minimise the incidence of colorectal carcinoma in this group.

What is the risk factor for metachronous colorectal carcinoma?

PURPOSE

The purpose of this study was to determine the risk factors for developing metachronous colorectal carcinoma and to determine an adequate postoperative colonoscopic surveillance.

METHODS

Two hundred eighty-four patients, examined by routine colonoscopy after resection for colorectal carcinoma, were reviewed. Clinical and pathologic factors were assessed by multiple logistic regression analysis.

RESULTS

One hundred eighty-three patients with synchronous adenoma or carcinoma at the initial operation had a significantly higher incidence of both metachronous adenoma and carcinoma than the 101 patients without a synchronous lesion. Other clinical factors including age, gender, tumor stage, tumor site, and tumor grade were not significant for an increased incidence of metachronous carcinoma. The presence of synchronous lesions proved to be the only risk factor (relative risk, 3.293; P = 0.0155) for developing metachronous carcinoma. Metachronous carcinoma was detected in 30 patients (10.6 percent) and completely removed from all patients. Mucosal carcinoma was found in 25 patients (8.8 percent) and invasive carcinoma in 5 patients (1.8 percent). All five invasive carcinomas were detected in asymptomatic patients having synchronous lesion. Four patients required a second operation for metachronous carcinoma more than 13 months following the first.

CONCLUSION

The risk factor for developing metachronous carcinoma is the presence of synchronous adenoma or carcinoma at the initial operation. To detect metachronous carcinoma at a curable stage, annual colonoscopic surveillance should be performed for high-risk patients.