Survival benefit in a randomized clinical trial of faecal occult blood screening for colorectal cancer

Factors that contribute to faecal cyclooxygenase-2 mRNA expression in subjects with colorectal cancer

Background:

We previously reported that a faecal cyclooxygenase-2 (COX-2) mRNA assay was useful for identifying colorectal cancer (CRC). This study sought to investigate the factors that contribute to faecal COX-2 mRNA expression in subjects with CRC.

Methods:

The study cohort comprised 78 patients with CRC and 36 control subjects. The expressions of COX-2, β-2-microglobulin (B2M), carcinoembryonic antigen (CEA), E-cadherin (E-cad), and CD45 mRNA in faeces and COX-2 mRNA expression in tissue were determined by quantitative real-time RT–PCR.

Results:

The level of faecal expression of COX-2 mRNA in CRC was significantly higher than that in controls. A significant correlation was found between faecal COX-2 mRNA expression and faecal B2M, CEA, E-cad, or CD45 mRNAs, markers of exfoliated total cells, colonocytes, and leukocytes, respectively. A significant correlation was found between the expression of COX-2 mRNA in faeces and tumour surface area, COX-2 mRNA expression in primary tumour. There was no difference in faecal COX-2 mRNA expression between proximal CRC and distal CRC.

Conclusion:

COX-2 mRNA expression in faeces seems to originate from tumour lesion and to be affected by factors such as the number of exfoliated cells, exfoliation of inflammatory cells, COX-2 mRNA expression in tumour, and tumour size.

[Chemical or immunological tests for the detection of fecal occult blood in colorectal cancer screening?]

Colorectal cancer (CRC) can be prevented by screening programs in the population at average risk (men and women aged between 50 and 74 years) and at high risk (first degree relatives, CRC hereditary syndromes and chronic inflammatory bowel disease). Early CRC (with submucosal invasion) and advanced adenomas (size > or =10mm, with severe dysplasia or >20% villous component) produce intermittent microscopic blood losses that can be detected through chemical and immunological testing for fecal occult blood (C-FOBT and I-FOBT). Among the screening strategies in the population at average risk, annual or biannual fecal occult blood testing is the most widely used due to its non-invasiveness and low cost. Four randomized clinical trials have shown that annual or biannual screening with guaiac-based tests (C-FOBT) reduces overall mortality due to CRC by 16% and CRC incidence by 20% and 17% respectively. However, these tests have major drawbacks, especially their low sensitivity in detecting early CRC and advanced adenoma, their lack of specificity in detecting human hemoglobin (Hb), and their high fecal Hb detection threshold (>300microgHb/gfeces). In the last few years, major developments have occurred in immunological tests (I-FOBT), based on an antigen-antibody reaction that specifically detects human Hb, and these tests are currently available as an alternative to C-FOBT. Their main advantages are as follows: firstly, I-FOBT specifically detect human Hb in stools and at much lower levels (40-300microgHb/gfeces) than C-FOBT; secondly, automated analysis avoids subjectivity in reading qualitative tests and allows large population groups to be studied in a short time, making I-FOBT ideal for population-based screening; thirdly, I-FOBT fairly accurately selects individuals for colonoscopy so that approximately half of patients with an I-FOBT test show clinically significant colorectal neoplasia (advanced adenoma or invasive CRC); fourthly, the cut-off point for fecal Hb detection can be modified, depending on the availability of endoscopic resources; fifthly, when cut-off points for fecal Hb of 50-150microgHb/gfeces are used, more than twice the number of CRC and advanced adenomas are detected than with C-FOBT, with a reasonable false-positive rate; and sixthly, I-FOBT are better accepted by the population due to their simplicity and ease of use, increasing participation in screening programs. For all these reasons, the current recommendation is that the new quantitative I-FOBT tests replace C-FOBT tests when the strategy of population-based screening through annual or biannual fecal occult blood testing is considered.

Câncer ano-reto-cólico: aspectos atuais IV - câncer de cólon - fatores clínicos, epidemiológicos e preventivos

O câncer colorretal tem alta incidência populacional e alto índice de mortalidade, com diferenças pouco relevantes entre os povos de diversas nações, como atestam os estudos epidemiológicos dessa doença. Embora a abordagem médico-cirúrgica do câncer colorretal tenha sido favorecida pelos novos conhecimentos adquiridos com a engenharia genética, pelos progressos que aprimoraram o tratamento, principalmente na área de neo-adjuvância, com as inovações nos aparelhos de radioterapia e com a constante introdução de novas e potentes substâncias quimioterápicas, o prognóstico da doença continua sombrio. Todavia, dados colhidos em estudos sobre a biologia do tumor - sua origem, crescimento e desenvolvimento e comportamento biológico - têm acenado para a possibilidade de cura quando os métodos preventivos, em prática, facilitam a abordagem precoce da lesão. Nesse contexto, o câncer colorretal é passível de cura, podendo, inclusive dispensar, para tanto, o tratamento adjuvante ou aliviar o paciente da abordagem cirúrgica mutilante. Assim, o maior esforço posto em ação no início desse século está sendo representado pelos movimentos de educação popular em massa para a prevenção do câncer de reto e dos cólons com incentivo para o teste de sangue oculto nas fezes.

Screening for colorectal cancer using the faecal occult blood test, Hemoccult

BACKGROUND

Colorectal cancer is a leading cause of morbidity and mortality, especially in the Western world. The human and financial costs of this disease have prompted considerable research efforts to evaluate the ability of screening tests to detect the cancer at an early curable stage. Tests that have been considered for population screening include variants of the faecal occult blood test, flexible sigmoidoscopy and colonoscopy. Reducing mortality from colorectal cancer (CRC) may be achieved by the introduction of population-based screening programmes.

OBJECTIVES

To determine whether screening for colorectal cancer using the faecal occult blood test (guaiac or immunochemical) reduces colorectal cancer mortality and to consider the benefits, harms and potential consequences of screening.

SEARCH STRATEGY

Published and unpublished data for this review were identified by: Reviewing studies included in the previous Cochrane review; Searching several electronic databases (Cochrane Library, Medline, Embase, CINAHL, PsychInfo, Amed, SIGLE, HMIC); and Writing to the principal investigators of potentially eligible trials.

SELECTION CRITERIA

We included in this review all randomised trials of screening for colorectal cancer that compared faecal occult blood test (guaiac or immunochemical) on more than one occasion with no screening and reported colorectal cancer mortality.

DATA COLLECTION AND ANALYSIS

Data from the eligible trials were independently extracted by two reviewers. The primary data analysis was performed using the group participants were originally randomised to ('intention to screen'), whether or not they attended screening; a secondary analysis adjusted for non-attendence. We calculated the relative risks and risk differences for each trial, and then overall, using fixed and random effects models (including testing for heterogeneity of effects). We identified nine articles concerning four randomised controlled trials and two controlled trials involving over 320,000 participants with follow-up ranging from 8 to 18 years.

MAIN RESULTS

Combined results from the 4 eligible randomised controlled trials shows that participants allocated to screening had a 16% reduction in the relative risk of colorectal cancer mortality (RR 0.84, CI: 0.78-0.90). In the 3 studies that used biennial screening (Funen, Minnesota, Nottingham) there was a 15% relative risk reduction (RR 0.85, CI: 0.78-0.92) in colorectal cancer mortality. When adjusted for screening attendance in the individual studies, there was a 25% relative risk reduction (RR 0.75, CI: 0.66 - 0.84) for those attending at least one round of screening using the faecal occult blood test.

AUTHORS' CONCLUSIONS

Benefits of screening include a modest reduction in colorectal cancer mortality, a possible reduction in cancer incidence through the detection and removal of colorectal adenomas, and potentially, the less invasive surgery that earlier treatment of colorectal cancers may involve. Harmful effects of screening include the psycho-social consequences of receiving a false-positive result, the potentially significant complications of colonoscopy or a false-negative result, the possibility of overdiagnosis (leading to unnecessary investigations or treatment) and the complications associated with treatment.