Estimation of screening test (Hemoccult) sensitivity in colorectal cancer mass screening

Contribution of the OC Sensor® immunoassay in comparison to the Hemoccult II® guaiac-test in organized colorectal cancer screening

Colorectal cancer (CRC) is a major cause of cancer-related death of worldwide with high incidence and mortality rate, accessible to a screening program in France, first with guaiac- based fecal occult blood test (g-FOBT) then with fecal immunochemical tests (FIT), since 2015, because of better accuracy. The aim of our study was to compare the characteristics of screen-detected lesions in two successive CRC screening campaigns, using two different tests (Hemoccult II^® and OC Sensor^®) in the department of Maine-et-Loire, and to precise the performance of these tests [participation rate, detection rates (DR), positive predictive value (PPV)]. Participants, invited by CAP SANTE 49, with polyps or cancer at the colonoscopy after a positive screening test between 01/01/2013 and 31/12/2016 were included. A guaiac-based fecal occult blood test (g-FOBT) was used from January 2013 to December 2014 and a FIT was used from June 2015 to December 2016). 2575 participants, 642 in g-FOBT group and 1933 in FIT group had lesions. Participation rate was not different between tests (p = 0.104), whereas DR and PPV were statistically higher in FIT for all lesions (2.61, 95% CI [2.50-2.70] vs 0.93, 95% CI [0.90-1.00], p < 0.0001 and 64.84, 95% CI [63.10-66.60], 50.00, 95% CI [47.30-52.70], p < 0.0001 respectively). FIT detects more precancerous lesions (adenomas, p < 0.001, and advanced adenomas, p < 0.001) than g-FOBT but g-FOBT detects more serrated polyps (p = 0.025). AAs were more in right colon in FIT than g-FOBT (p = 0.035). No different participation rate was detected between FIT and g-FOBT but DR and PPV of all lesions was higher with FIT.

Temporal trends in postcolonoscopy colorectal cancer rates in 50- to 74-year-old persons: a population-based study

BACKGROUND AND AIMS

Colorectal cancers (CRCs) diagnosed between 6 and 36 months after colonoscopy, termed postcolonoscopy CRCs (PCCRCs), arise primarily due to missed or inadequately treated neoplasms during colonoscopy. Introduction of multiple quality indicators and technological advances to colonoscopy practice should have reduced the PCCRC rate over time. We assessed temporal trends in the population rate of PCCRC as a measure of changing colonoscopy quality.

METHODS

We conducted a population-based retrospective cohort study of persons aged 50 to 74 years without advanced risk factors for CRC who underwent complete colonoscopy in Ontario, Canada between 1996 and 2010. We defined the PCCRC rate as the proportion of individuals diagnosed with CRC within 36 months of colonoscopy that had PCCRC. We compared age-adjusted and sex-adjusted rates of PCCRC over time based on 3 periods (1996-2001, 2001-2006 and 2006-2010) and assessed the independent association between time period and PCCRC risk through multivariable regression, with respect to all PCCRCs, proximal PCCRC and distal PCCRC.

RESULTS

There was a marked increase in colonoscopy volumes over the study period, particularly in younger age groups and non-hospital settings. Among 1,093,658 eligible persons the PCCRC rate remained stable at approximately 8% over the 15-year study period. The adjusted odds of PCCRC, distal PCCRC and proximal PCCRC, comparing the 2006 to 2010 period with the 1996 to 2001 period, were 1.14 (95% confidence interval [CI], 1.0-1.31), 1.11 (95% CI, 0.91-1.34), and 1.14 (95% CI, 0.94-1.38), respectively. Temporal trends in PCCRC risk did not differ by endoscopist specialty or institutional setting after covariate adjustment.

CONCLUSION

The PCCRC rate in Ontario has remained consistently high over time. Widespread initiatives are needed to improve colonoscopy quality.

Predicting the effectiveness of the Finnish population-based colorectal cancer screening programme

Objective

Because colorectal cancer (CRC) has a long natural history, estimating the effectiveness of CRC screening programmes requires long-term follow-up. As an alternative, we here demonstrate the use of a temporal multi-state natural history model to predict the effectiveness of CRC screening.

Methods

In the Finnish population-based biennial CRC screening programme using faecal occult blood tests (FOBT), which was conducted in a randomised health services study, we estimated the pre-clinical incidence, the mean sojourn time (MST), and the sensitivity of FOBT using a Markov model to analyse data from 2004 to 2007. These estimates were applied to predict, through simulation, the effects of five rounds of screening on the relative rate of reducing advanced CRC with 6 years of follow-up, and on the reduction in mortality with 10 years of follow-up, in a cohort of 500,000 subjects aged 60 to 69.

Results

For localised and non-localised CRC, respectively, the MST was 2.06 and 1.36 years and the sensitivity estimates were 65.12% and 73.70%. The predicted relative risk of non-localised CRC and death from CRC in the screened compared with the control population was 0.86 (95% CI: 0.79–0.98) and 0.91 (95% CI: 0.85–1.02), respectively.

Conclusion

Based on the preliminary results of the Finnish CRC screening programme, our model predicted a 9% reduction in CRC mortality and a 14% reduction in advanced CRC.

Population-based assessment of the outcomes in patients with postcolonoscopy colorectal cancers

OBJECTIVE

The potential for cancers to not be detected on colonoscopy is increasingly recognised, but little is known about patient outcomes. The objective of this study was to assess the outcomes of patients diagnosed with postcolonoscopy colorectal cancers (PCCRCs).

DESIGN

We conducted a population-based retrospective cohort study, including all patients diagnosed with colorectal cancer (CRC) in Ontario, Canada from 2003 to 2009. Patients were categorised into three groups: DETECTED (diagnosed within 6 months of first colonoscopy), PCCRC (diagnosed 6-36 months after first colonoscopy) or NOSCOPE (no colonoscopy within 36 months of diagnosis). Univariate and multivariable analyses were conducted to study overall survival, surgical treatment, emergency presentation and surgical complications.

RESULTS

Overall, 45 104 patients were included, with 2804 being classified as having a PCCRC. Compared with the DETECTED group, PCCRC was associated with a significantly higher likelihood of stage IV disease (17.2% vs 12.9%), worse overall survival (5 year OS: 60.8% vs 68.3%, p<0.0001; adjusted HR: 1.25, 95% CI 1.17 to 1.32, p<0.0001), a higher likelihood of emergency presentation (OR: 2.86, 95% CI 2.56 to 3.13, p<0.001) and lower likelihood of surgical resection (OR: 0.61, 95% CI 0.55 to 0.67, p<0.001). However, patients with PCCRC had significantly better outcomes than those in the NOSCOPE group (stage IV: 37.1%, 5 year OS: 38.9%)

CONCLUSIONS

Compared with CRC detected by colonoscopy, PCCRCs are associated with a higher risk of emergent presentation, a lower likelihood of surgical resection and most notably, significantly worse oncological outcomes. However, they have better outcomes than patients with no recent colonoscopy.

No decrease in the rate of early or missed colorectal cancers after colonoscopy with polypectomy over a 10-year period: a population-based analysis

BACKGROUND & AIMS

It is not clear whether the incidence of missed or early colorectal cancers (CRCs) has decreased over time. We compared the rates of missed or early CRC after polypectomy between 1996 and 2006, and aimed to identify risk factors for these.

METHODS

We performed a population-based, case-control study linking data from the Dutch Pathology Registry with data from The Netherlands Cancer Registry. Of all patients with an incident CRC in 1996 and 2006, we identified whether colonic histology specimens were available in the preceding 3 years. Patients with early or missed CRC were defined as those with previous colonic histology in the 6 to 36 months preceding CRC diagnosis. We performed multivariate logistic regression analysis to identify factors associated with missed or early CRCs.

RESULTS

CRC was diagnosed in 6941 patients in 1996 and in 10,963 patients in 2006. The proportion of patients with early or missed CRC was 1.7% of all CRC patients in 1996 and 2.3% in 2006 (P = .012). Early or missed CRCs had a lower tumor, nodal, and metastasis stage than regularly diagnosed CRCs (P < .001), but rate of survival, adjusted for TNM stage, did not differ. CRCs of the right colon and transverse colon and splenic flexure were associated with a missed or early CRC (odds ratio [OR], 2.34; 95% confidence interval [CI], 1.80-3.05; and OR, 2.14; 95% CI, 1.49-3.08, respectively), as was male sex (OR, 1.31; 95% CI, 1.06-1.62).

CONCLUSIONS

Based on an analysis of the Dutch population, there has been no decrease in the occurrence of missed or early CRCs over a 10-year period. Location in the right side of the colon was an independent risk factor for missed or early CRCs.

Estimated mean sojourn time associated with hemoccult SENSA for detection of proximal and distal colorectal cancer

BACKGROUND

Sojourn time is the length of the preclinical screen-detectable phase, a period when a test can detect asymptomatic disease. Mean sojourn time (MST) is an important factor in determining appropriate screening intervals. Available estimates of MST for colorectal cancer (CRC) are imprecise and are associated with the older Hemoccult II test. This article presents MST estimates associated with the newer Hemoccult SENSA test and describes differences in MST by the location of cancer in the colorectum and age at the time of screening.

METHODS

MST was estimated from a cohort of 42,079 patients who underwent Hemoccult SENSA between January 1, 1997 and December 31, 2010. The precision of MST estimates was improved by incorporating information from a meta-analysis of the sensitivity of Hemoccult SENSA into the analytic model.

RESULTS

Estimated MST for cancers in the proximal and distal colorectum, with 95% credible intervals (CrI) in years, were: 3.86 (1.55-6.91) and 3.35 (2.11-4.93) among 45- to 54-year olds; 3.78 (2.18-5.77) and 2.24 (1.48-3.17) among 55- to 64-year olds; and 2.70 (1.41-4.31) and 2.10 (1.34-3.04) among 65- to 74-year olds.

CONCLUSIONS

MST associated with Hemoccult SENSA was longer for CRC in the proximal versus distal colon. We found no evidence that MST increases with age and some evidence that it may decrease.

IMPACT

These results add new information about the natural history of CRC and information about the performance of Hemoccult SENSA.

Colonoscopic polypectomy and long-term prevention of colorectal-cancer deaths

BACKGROUND

In the National Polyp Study (NPS), colorectal cancer was prevented by colonoscopic removal of adenomatous polyps. We evaluated the long-term effect of colonoscopic polypectomy in a study on mortality from colorectal cancer.

METHODS

We included in this analysis all patients prospectively referred for initial colonoscopy (between 1980 and 1990) at NPS clinical centers who had polyps (adenomas and nonadenomas). The National Death Index was used to identify deaths and to determine the cause of death; follow-up time was as long as 23 years. Mortality from colorectal cancer among patients with adenomas removed was compared with the expected incidence-based mortality from colorectal cancer in the general population, as estimated from the Surveillance Epidemiology and End Results (SEER) Program, and with the observed mortality from colorectal cancer among patients with nonadenomatous polyps (internal control group).

RESULTS

Among 2602 patients who had adenomas removed during participation in the study, after a median of 15.8 years, 1246 patients had died from any cause and 12 had died from colorectal cancer. Given an estimated 25.4 expected deaths from colorectal cancer in the general population, the standardized incidence-based mortality ratio was 0.47 (95% confidence interval [CI], 0.26 to 0.80) with colonoscopic polypectomy, suggesting a 53% reduction in mortality. Mortality from colorectal cancer was similar among patients with adenomas and those with nonadenomatous polyps during the first 10 years after polypectomy (relative risk, 1.2; 95% CI, 0.1 to 10.6).

CONCLUSIONS

These findings support the hypothesis that colonoscopic removal of adenomatous polyps prevents death from colorectal cancer. (Funded by the National Cancer Institute and others.).

Rate and predictors of early/missed colorectal cancers after colonoscopy in Manitoba: a population-based study

OBJECTIVES

Many of the colorectal cancers (CRCs) diagnosed within 3 years after a colonoscopy are likely because of lesions missed on the initial colonoscopy. In this population-based study, we investigated the rate and predictors of CRCs diagnosed within 3 years of a colonoscopy.

METHODS

We identified individuals 50-80 years of age diagnosed with CRC between 1992 and 2008 from the provincewide Manitoba Cancer Registry. Performance of colonoscopy and history of co-morbidities was determined by linkage to the provincial universal health care insurance provider's physician billing claims and hospital discharges databases. CRCs diagnosed within 6 months of a colonoscopy were categorized as detected CRCs and those 6-36 months after a colonoscopy as early/missed CRCs. Logistic regression analysis was performed to identify the patient, endoscopist, colonoscopy, and CRC factors associated with early/missed CRCs.

RESULTS

Of the 4,883 CRCs included in the study, 388 (7.9%) were early/missed CRCs, with a range of 4.5% of rectum/rectosigmoid cancers in men to 14.4% of transverse colon/splenic flexure cancers in women. Independent risk factors associated with early/missed CRCs included prior colonoscopy, performance of index colonoscopy by family physicians, recent year of CRC diagnosis, and proximal site of CRC.

CONCLUSIONS

This study suggests that approximately 1 in 13 CRCs may be an early/missed CRC, diagnosed after an index colonoscopy in usual clinical practice. Women are more likely to have early/missed CRC. It is unclear if this relates to differences in procedure difficulty, bowel preparation issues, or tumor biology between men and women.

Gastroscopy following a positive fecal occult blood test and negative colonoscopy: systematic review and guideline

BACKGROUND

A sizeable number of individuals who participate in population-based colorectal cancer (CRC) screening programs and have a positive fecal occult blood test (FOBT) do not have an identifiable lesion found at colonoscopy to account for their positive FOBT screen.

OBJECTIVE

To evaluate the evidence and provide recommendations regarding the use of routine esophagogastroduodenoscopy (EGD) to detect upper gastrointestinal (UGI) cancers in patients participating in a population-based CRC screening program who are FOBT positive and colonoscopy negative.

METHODS

A systematic review was used to develop the evidentiary base and to inform the evidence-based recommendations provided.

RESULTS

Nine studies identified a group of patients who were FOBT positive and colonoscopy negative. Three studies found no cases of UGI cancer. Four studies reported cases of UGI cancer; three found UGI cancer in 1% or less of the population studied, and one study found one case of UGI cancer that represented 7% of their small subgroup of FOBT-positive/colonoscopy-negative patients. Two studies did not provide outcome information that could be specifically related to the FOBT-positive/colonoscopy-negative subgroup.

CONCLUSION

The current body of evidence is insufficient to recommend for or against routine EGD as a means of detecting gastric or esophageal cancers for patients who are FOBT positive/colonoscopy negative, in a population-based CRC screening program. The decision to perform EGD should be individualized and based on clinical judgement.

Predictors of colorectal cancer after negative colonoscopy: a population-based study

OBJECTIVES

A higher proportion of colorectal neoplasia among women occurs in the proximal colon, which might be more frequently missed by colonoscopy. There are no data on predictors of developing colorectal cancer (CRC) after a negative colonoscopy in usual clinical practice. We evaluated gender differences and predictors of CRC occurring after a negative colonoscopy.

METHODS

All individuals 40 years or older with negative colonoscopy were identified from Manitoba's provincial physicians' billing claims database. Individuals with less than 5 years of coverage by the provincial health plan, earlier CRC, inflammatory bowel disease, resective colorectal surgery, or lower gastrointestinal endoscopy were excluded. CRC risk after negative colonoscopy was compared to that in the general population by standardized incidence ratios. Cox regression analysis was performed to determine the independent predictors of CRC occurring after negative colonoscopy.

RESULTS

A total of 45,985 individuals (18,606 men; 27,379 women) were followed up for 229,090 person-years. After a negative colonoscopy, men had a 40-50% lower risk of CRC diagnosis through most of the follow-up time. Risk among women was similar to that of women in the general population in the first 3 years and then was 40-50% lower. Older subject age and performance of index colonoscopy by non-gastroenterologists were independent predictors for early/missed CRC (cancers occurring within 3 years of negative colonoscopy).

CONCLUSIONS

Women may have a higher rate of missed/early CRCs after negative colonoscopy. Predictors of missed/early CRCs after negative colonoscopy include older age and performance of index colonoscopy by a non-gastroenterologist.

Cost-effectiveness of screening for colorectal cancer in France using a guaiac test versus an immunochemical test

Objectives: The aim of this study was to compare the cost and the effectiveness of two biennial fecal occult blood screening tests for colorectal cancer: a guaiac nonrehydrated test (G-FOBT) and an immunochemical test (I-FOBT) with the absence of screening.

Methods: A Markov model was developed to compare these strategies in a general population of subjects aged 50 to 74 over a 20-year period.

Results: Compared with the absence of screening, G-FOBT and I-FOBT were associated with a decrease in colorectal cancer mortality of 17.4 percent and 25.2 percent, respectively. With regard to cost-effectiveness, expressed as cost per life-year gained, I-FOBT was the most effective and most costly alternative. Compared with no screening, G-FOBT and I-FOBT presented similar discounted incremental cost-effectiveness ratios: €2,739 and €2,819 respectively per life-year gained. When compared with G-FOBT, I-FOBT presented an incremental cost-effectiveness ratio of €2,988 per life-year gained. Sensitivity analyses showed the strong influence of the I-FOBT lead time, of the participation rate to screening for I-FOBT, and of the purchase price of the I-FOBT on the discounted incremental cost-effectiveness ratios.

Conclusions: Compared with the absence of screening and with G-FOBT, the biennial two-stool immunochemical test can be considered a promising method for mass screening for colorectal cancer.

[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.

Sensitivity of latex agglutination faecal occult blood test in the Florence District population-based colorectal cancer screening programme

We evaluated the sensitivity for colorectal cancer (CRC) of the latex agglutination test (LAT), an immunochemical test routinely used in the Florence District screening programme since 2000. Sensitivity was calculated by the proportional interval cancer incidence method in a population of 27,503 consecutive subjects screened in 2000-2002, interval cancers being identified by linkage to the Tuscany Cancer Registry files. Sensitivity was calculated overall and by gender, age, time since last negative LAT, CRC site, and rank of screening. Overall 1- and 2-year sensitivity estimates were 80.7 and 71.5%, respectively, suggesting that faecal occult blood testing screening sensitivity may be suboptimal due to testing or programme quality problems. Increasing screening sensitivity might be achieved if the detection rate of advanced adenomas could be increased without unacceptable loss in specificity.

Evaluation of a combined screening programme for breast, cervical and colorectal cancers in France

A combined breast, cervical and colorectal cancer screening programme was set up in 1990 in Isère, for women aged 50-69 years (target population 100,000) comprising an initial medical visit. The programme was evaluated in 1997. The evaluation covered uptake results, sensitivity, specificity, two opinion surveys among 1025 physicians and 400 women to measure the impact, and three surveys regarding radiologists', gastroenterologists' and pathologists' attitudes. Sensitivity and specificity rates were 74 and 87% for breast, 83 and 99% for cervical and 43 and 97% for colorectal screening. The number of cervical smears completed by women aged 60-69 years doubled with the programme. Acceptability of the faecal occult blood test was 88%. Eighty percent of physicians were in favour of the programme but 67% said that they often prescribed outside the programme. Overall, 71% of the interviewed women said they had had a breast screen, 69% a Pap smear and 53% a faecal occult blood test when only 25-35% of the target population was actually recorded in the programme. This programme increased the uptake of women not previously screened both within and outside the programme. It showed discrepancies between beliefs and practices of physicians. Protocol changes were implemented after this evaluation.

Rates of new or missed colorectal cancers after colonoscopy and their risk factors: a population-based analysis

BACKGROUND & AIMS

The rate of new or missed colorectal cancer (CRC) after colonoscopy and their risk factors in usual practice are unknown. Our objective was to evaluate the rate and risk factors in a population-based study.

METHODS

We analyzed data from the Canadian Institute for Health Information, the Ontario Health Insurance Program, and Ontario Cancer Registry for all patients (> or =20 years of age) with a new diagnosis of right-sided, transverse, splenic flexure/descending, rectal or sigmoid CRC in Ontario from April 1, 1997 to March 31, 2002, who had a colonoscopy within the 3 years before their diagnosis. Patients with new or missed cancers were those whose most recent colonoscopy was 6 to 36 months before diagnosis. We examined characteristics that might be risk factors for new or missed CRC.

RESULTS

We identified a diagnosis of CRC in 3288 (right sided), 777 (transverse), 710 (splenic flexure/descending), and 7712 (rectal or sigmoid) patients. The rates of new or missed cancers were 5.9%, 5.5%, 2.1%, and 2.3%, respectively. Independent risk factors for these cancers in men and women were older age; diverticular disease; right-sided or transverse CRC; colonoscopy by an internist or family physician; and colonoscopy in an office.

CONCLUSIONS

Because having an office colonoscopy and certain patient, procedure, and physician characteristics are independent risk factors for new or missed CRC, physicians must inform patients of the small risk (2% to 6%) of these cancers after colonoscopy. The influence of type of physician and setting on the accuracy of colonoscopy, potentially modifiable risk factors, warrants further study.

Low compliance with colonoscopic screening in first-degree relatives of patients with large adenomas

BACKGROUND

Little is known about compliance with colonoscopy as a screening method in first-degree relatives of patients with large adenomas. Aims To evaluate the compliance with screening colonoscopy among this population, and its determinants.

METHODS

Data were obtained from the family part of the GEADE study, a study on genetic factors of colorectal adenomas. Index cases were 306 patients with adenomas > or = 10 mm. All living first-degree relatives aged 40-75 who could be contacted by the index case were asked to undergo a colonoscopy, unless they had had one in the previous 5 years.

RESULTS

Among 674 eligible relatives, 56 had had a colonoscopy within the preceding 5 years and 114 underwent a screening colonoscopy resulting in a compliance with screening colonoscopy of 18%. This was not related to most characteristics of index cases. Compliance was significantly lower when the index case lived in the Greater Paris area than when he/she lived in other areas (12% vs. 21%). It was higher in siblings (18%) and offspring (23%) than in parents (9%) and in relatives under 55 years old (22%) than in relatives aged 55 and over (15%).

CONCLUSIONS

Compliance with colonoscopy was low in first-degree relatives of patients with large adenomas. The reasons for this should be determined and appropriate strategies developed to increase compliance.

Cost-effectiveness analysis of colorectal cancer screening with stool DNA testing in intermediate-incidence countries

Background

The aim of this study is to compare the cost-effectiveness of screening with stool DNA testing with that of screening with other tools (annual fecal occult blood testing, flexible sigmoidoscopy every 5 years, and colonoscopy every 10 years) or not screening at all.

Methods

We developed a Markov model to evaluate the above screening strategies in the general population 50 to 75 years of age in Taiwan. Sensitivity analyses were performed to assess the influence of various parameters on the cost-effectiveness of screening. A third-party payer perspective was adopted and the cost of $13,000 per life-year saved (which is roughly the per capita GNP of Taiwan in 2003) was chosen as the ceiling ratio for assessing whether the program is cost-effective.

Results

Stool DNA testing every three, five, and ten years can reduce colorectal cancer mortality by 22%, 15%, and 9%, respectively. The associated incremental costs were $9,794, $9,335, and $7,717, per life-year saved when compared with no screening. Stool DNA testing strategies were the least cost-effective with the cost per stool DNA test, referral rate with diagnostic colonoscopy, prevalence of large adenoma, and discount rate being the most influential parameters.

Conclusion

In countries with a low or intermediate incidence of colorectal cancer, stool DNA testing is less cost-effective than the other currently recommended strategies for population-based screening, particularly targeting at asymptomatic subjects.

Evaluation of an immunochemical fecal occult blood test with automated reading in screening for colorectal cancer in a general average-risk population

Colorectal cancer screening is a high public health priority in all industrialized countries. However, the low sensitivity of the common guaiac screening test (HemoccultII) makes practitioners and public health decision makers reluctant to set up a national screening program. In recent years, immunochemical tests based on the use of a specific antibody have been found to be more sensitive than the HemoccultII test. However, for screening purposes, any gain in sensitivity is of interest only if specificity and positive predictive value are satisfactory. Our aim was to assess the performance of an immunochemical test with an automated reading technique (Magstream 1000) for different hemoglobin content cut-off points. The study was carried out in the general population aged 50-74 years in the geographic area of Cotentin (Normandy, France). From 1 January 2001 to 31 December 2002, 7,421 one-time screening tests (Magstream) were administered by general practitioners and occupational physicians to patients at the end of regular consultations. Colonoscopy was proposed to the 434 people with a positive test. All cancers occurring in the study population between 1 January 2001 and 31 December 2003 were collected by general practitioners, gastroenterologists and the local registry. At the usual positivity threshold (20 ng hemoglobin/ml), screening sensitivity and specificity at 2 years of follow-up with 95% CIs were, respectively, 0.85 (0.72-0.98) and 0.94 (0.94-0.95). If the hemoglobin content cut-off point had been set at 50 ng/ml instead of the usual cut-off, positivity would have been 3.1% and positive predictive value for a cancer or a large adenoma would have been 0.49, with sensitivity of 0.68-0.83 and specificity of 0.97. Our results suggest that use of an immunochemical test with an automated reading technique could improve the prospects for mass-screening for colorectal cancer since it offers a promising alternative to guaiac tests.

Cost-effectiveness analysis of fecal occult blood screening for colorectal cancer

OBJECTIVES

Clinical trials have demonstrated that fecal occult blood screening for colorectal cancer can significantly reduce mortality. However, to be deemed a priority from a public health policy perspective, any new program must prove itself to be cost-effective. The objective of this study was to assess the cost-effectiveness of screening for colorectal cancer using a fecal occult blood screening test, the Hemoccult-II, in a cohort of 100,000 asymptomatic individuals 50-74 years of age.

METHODS

A decision analysis model using a Markov approach simulates the trajectory of the cohort allocated either to screening or no screening over a 20-year period through several health states. Clinical and economic data used in the model came from the Burgundy trial, French population-based studies, and Registry data.

RESULTS

Modeling biennial screening versus the absence of screening over a 20-year period resulted in a 17.7 percent mortality reduction and a discounted incremental cost-effectiveness ratio of 3357 Euro per life-year gained among individuals 50-74 years of age. Sensitivity analyses performed on epidemiological and economic data showed the strong impact on the results of colonoscopy cost, of compliance to screening, and of specificity of the screening test.

CONCLUSIONS

Cost-effectiveness estimates and sensitivity analyses suggest that biennial screening for colorectal cancer with fecal occult blood test could be recommended from the age of 50 until 74. Our findings support the attempts to introduce large-scale population screening programs.

Molecular stool screening for colorectal cancer

BACKGROUND

Mass screening for colorectal cancer reduces mortality and, with recent advances in molecular genetics, molecular stool-based tests have produced promising results. This article reviews this innovation and discusses its clinical significance.

METHODS

Medline searches were used to identify recent key articles relating to stool-based testing. Further articles were obtained by manual scanning of the reference lists of identified papers.

RESULTS

Current screening methods are based on endoscopic, radiological and stool-based testing. Recent recognition of the adenoma-carcinoma sequence and pathophysiological studies of colonic epithelium have enabled tumour markers to be used in the screening setting. Non-invasive molecular stool testing has now been shown to have a high sensitivity and specificity.

CONCLUSION

Recent studies on molecular stool-based testing have shown higher sensitivity and specificity than earlier studies, but larger clinical trials are required. Laboratory methods are still undergoing research, with the aim of improving sensitivity to allow large-scale testing.

Modeling recurrence in colorectal cancer

OBJECTIVE

To assess the role of recurrence in prognosis of colon cancer, we investigated several methodologic issues, including application of classic survival analysis and Markov model.

STUDY DESIGN AND SETTING

The data were recorded by the Registry of Digestive Tumors of Côte d'Or, France, for 874 patients who had been treated by surgery between 1976 and 1984 and followed for up to 11 years. Survival analyses included the Cox proportional hazards model and its two generalizations that allow recurrence to be taken into account as a time-dependent covariate or as a competing outcome. The Markov model was used to analyze simultaneously recurrence and death.

RESULTS

The competing risks approach is not appropriate because censoring is indisputably informative. The Markov model and the Cox model, with recurrence as a time-dependent covariate, provided similar results, demonstrating the impact of age and gender on recurrence and revealing a reduction in the effect of site and stage on mortality.

CONCLUSION

A Markov multistate model seems to give new insights about the course of digestive cancer progression and into the role of recurrence in this process.

A simulation model for evaluating the medical and economic outcomes of screening strategies for colorectal cancer

Mathematical models have been shown to be useful in predicting the cost-effectiveness of cancer screening programmes. We designed a computer macro-simulation model aimed at predicting the cost-effectiveness of alternative colorectal cancer screening strategies. This model was built to determine the cost-effectiveness of a biennial screening programme using the Hemoccult test in Burgundy (France). It was validated with data from the Danish randomized study. Estimates of our model showed an extremely close concordance with observed results in the Danish study. The observed mortality reduction was 18.0% and the estimated mortality reduction was 18.4%. Preliminary data from the Burgundy study predict a 14.6% colorectal cancer mortality reduction after 10 years. Sensitivity analyses were performed with different assumptions regarding the participation rates and the lead-time. This model can serve to assess the cost-effectiveness of a variety of screening modalities.

Epidemiology and screening of colorectal cancer

Knowledge of the descriptive epidemiology of colorectal cancer is essential to a better understanding of the aetiology of the disease and the development of screening strategies. Considerable research efforts have been launched over the last 15 years to evaluate the ability of screening tests to decrease the incidence and mortality of colorectal cancer. This chapter provides a worldwide update of the incidence of colorectal cancer and reviews the evidence for screening for colorectal cancer based on published studies.