Molecular tests for colorectal cancer screening

Detecting and removing high-risk adenomas and early colorectal cancer (CRC) can reduce mortality of this disease. The noninvasive fecal occult blood test (FOBT; guaiac-based or immunochemical) is widely used in screening programs and although effective, it leaves room for improvement in terms of test accuracy. Molecular tests are expected to be more sensitive, specific and informative than current detection tests, and are promising future tools for CRC screening. This review provides an overview of the performances of DNA, RNA, and protein markers for CRC detection in stool and blood. Most emphasis currently is on DNA and protein markers. Among DNA markers there is trend to move away from mutation markers in favor of methylation markers. The recent boost in proteomics research leads to many new candidate protein markers. Usually in small series, some markers show better performance than the present FOBT. Evaluation in large well-controlled randomized trials is the next step needed to take molecular markers for CRC screening to the next level and warrant implementation in a screening setting.     

Novel molecular screening approaches in colorectal cancer

Traditional methods for colorectal cancer (CRC) screening have reduced rates of malignancy and death; however, low compliance and morbidities associated with invasive techniques have encouraged efforts for establishing equally effective, less invasive novel screening approaches. We review the current state of novel screening approaches in CRC to include CT colonography, fecal DNA, DNA methylation, micro-RNA, and protein and molecular markers.     

粪便DNA检测在结直肠癌筛查中的研究进展

粪便DNA检测筛查结直肠癌(colorectal cancer,CRC)具有非侵入性、患者依从性好、高敏感性和高特异性等优点,目前已从早期的单基因检测发展到多基因联合检测,可能成为CRC筛查和早期诊断的重要辅助手段。本文就粪便DNA检测在结直肠癌筛查中的研究进展作一综述。     

Nonsurgical approaches to colorectal cancer

It is time to challenge the current orthodoxy that frowns upon surgical and nonsurgical methods of tumor reduction for patients with metastatic colon cancer. Although the studies conducted with radiofrequency ablation, chemoembolization, and radiation therapy in patients with metastatic colon cancer have tended to be small and may have been subject to selection bias, they have produced survival data that require careful consideration. At the very least, it is clear that locoregional approaches to debulking tumors are feasible and that their combination with systemic chemotherapy should be investigated.     

A sensitive method to quantify human long DNA in stool: relevance to colorectal cancer screening.

Human long DNA in stool may reflect nonapoptotic exfoliation and has been used as a colorectal cancer (CRC) marker. Targeting human-specific Alu repeats represents a logical but untested approach. A real-time Alu PCR assay was developed for quantifying long human DNA in stool and evaluated in this study. The accuracy and reproducibility of this assay and the stability of long DNA during room temperature fecal storage were assessed using selected patient stools and stools added to human DNA. Thereafter, long DNA levels were determined in blinded fashion from 18 CRC patients and 20 colonoscopically normal controls. Reproducibility of real-time Alu PCR for quantifying fecal long DNA was high (r2 = 0.99; P < 0.01). Long DNA levels in nonbuffered stools stored at room temperature fell a median of 75% by 1 day and 81% by 3 days. An EDTA buffer preserved DNA integrity during such storage. Human long DNA was quantifiable in all stools but was significantly higher in stools from CRC patients than from normal controls (P < 0.05). At a specificity of 100%, the sensitivity of long DNA for CRC was 44%. Results indicate that real-time Alu PCR is a simple method to sensitively quantify long human DNA in stool. This study shows that not all CRCs are associated with increased fecal levels of long DNA. Long DNA degrades with fecal storage, and measures to stabilize this analyte must be considered for optimal use of this marker.     

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.     

Colorectal cancer screening: prospects for molecular stool analysis

Colorectal cancer is common. As many patients present with advanced disease, an effective screening test would have substantial clinical benefits. Recent progress in understanding the biology of colorectal cancer (and of cancer cells in general) has led to possible new approaches to screening. In particular, there are prospects of developing tests based on analysis of stool, which promise improved accuracy, safety, affordability and patient compliance.     

New stool tests for colorectal cancer screening: a systematic review focusing on performance characteristics and practicalness

New stool tests may be promising tools for future colorectal cancer (CRC) screening. The aim of this review was to summarize current evidence of performance characteristics and practicalness in a population-based screening setting of recently developed stool tests. The MEDLINE database was searched for relevant articles published until July 2004. Studies were included if they comprised more than 10 cases and more than 10 controls. Details on study population, performance characteristics and stool collection procedure were taken into account. Overall, 29 studies, mostly retrospective, were included, investigating 17 different stool markers or marker combinations. Underlying study populations were very heterogeneous and mostly very small. Half of the studies reported sensitivity for adenomas in addition to sensitivity for CRC, and fewer than half reported sensitivity by tumor stage or location. Performance characteristics of stool tests varied to a large extent. For most DNA-based markers, specificity was about 95% or higher, but sensitivity was mostly low even for invasive CRC. More studies with larger sample sizes were done for protein-based markers, which typically had lower specificity. In most studies, stool samples were frozen within a rather short time period after defecation. While promising performance characteristics have been reported for some tests, more pervasive evidence from larger, prospectively designed studies, which also consider aspects of practicalness, e.g., the possibility of mailing the samples, is needed.     

Detecting K-ras mutations in stool from fecal occult blood test cards in multiphasic screening for colorectal cancer

Fecal occult blood testing (FOBT) is proven an efficient way of reducing mortality from colorectal cancer but has a relatively low positive predictive value (PPV). This study evaluated the ability to detect K-ras mutations in stool DNA from FOBT cards and to improve the PPV of the screening process. Two hundred and five consecutive positive FOBT cards and an arbitrary sample of 38 negative cards from a population-based screening program were included. K-ras mutations in FOBT card stool were sought using allele-specific hybridization. DNA was successfully amplified from 87.2% of cards. In 130 cases with positive FOBT and amplifiable DNA 23 malignancies and 25 adenomas were detected. In 34.8% of the malignancies, a mutation in K-ras was detected. The PPV for malignancies increased from 17.7% (all positive cards) to 60.0% if cards with four or more fields were positive and K-ras was positive (RR=2.66, 95% CI: 1.2-6.1). Testing for K-ras mutations in DNA extracted from stool from positive FOBT cards is feasible. Sequential detection of cancer-associated genetic markers from FOBT-based stool samples may potentially help separate true from false positives in a FOBT-based screening process.     

Fecal DNA testing for colorectal cancer screening: Molecular targets and perspectives

The early detection of colorectal cancer with effective screening is essential for reduction of cancer-specific mortality. The addition of fecal DNA testing in the armamentarium of screening methods already in clinical use launches a new era in the noninvasive part of colorectal cancer screening and emanates from a large number of previous and ongoing clinical investigations and technological advancements. In this review, we discuss the molecular rational and most important genetic alterations hallmarking the early colorectal carcinogenesis process. Also, representative DNA targets-markers and key aspects of their testing at the clinical level in comparison or/and association with other screening methods are described. Finally, a critical view of the strengths and limitations of fecal DNA tests is provided, along with anticipated barriers and suggestions for further exploitation of their use.     

Molecular methods for colorectal cancer screening: Progress with next-generation sequencing evolution

Currently, colorectal cancer(CRC) represents the third most common malignancy and the second most deadly cancer worldwide, with a higher incidence in developed countries. Like other solid tumors, CRC is a heterogeneous genomic disease in which various alterations, such as point mutations, genomic rearrangements, gene fusions or chromosomal copy number alterations, can contribute to the disease development. However, because of its orderly natural history, easily accessible onset location and high...     

A simulation model for colorectal cancer screening: potential of stool tests with various performance characteristics compared with screening colonoscopy.

OBJECTIVE: Many new stool tests intended to detect neoplastic cells or cell products are developed at present for colorectal cancer (CRC) screening. The aim of this study was to simulate a population-based screening setting to assess and compare the potential for early detection and prevention of CRC of screening based on stool tests with different sensitivity and specificity and of screening with colonoscopy as a primary screening tool. METHOD: A Markov model was developed aimed to estimate the proportion of CRC cases which are early detected or prevented due to screening as well as the number of equired stool tests and colonoscopies per early detected or prevented CRC case. Model outcomes were calculated for the offer of annual stool testing from age 55 to 74 in combination with colonoscopic follow-up of positive test results and for the offer of screening colonoscopy as a primary screening tool at ages 55 and 65. The long-lasting risk reduction of colonoscopy allowing the removal of precancerous lesions was taken into account quantitatively. RESULTS: For a variety of stool tests with different performance characteristics, the proportion of CRC cases early detected or prevented was estimated to be higher for stool testing in combination with colonoscopic follow-up of positive test results compared with screening colonoscopy assuming levels of compliance to be expected for the respective screening scheme. Optimizing performance characteristics of stool tests in terms of detecting precancerous lesions, in addition to those in terms of detecting CRC, seemed to be crucial for maximizing effectiveness of CRC screening with stool tests. CONCLUSION: Screening based on new stool tests with colonoscopic follow-up of positive test results might offer a high potential for early detection or prevention of CRC.     

Molecular approaches to lung cancer evaluation

The stagnation of therapeutic results in lung cancer over the last decade(s) is a matter of great concern, also due to the constantly increasing incidence of the disease. Among the reasons for this failing therapeutic progress is the lack of understanding of the molecular mechanisms underlying the disease. Presently molecular biology techniques contribute to the deciphering of these mechanisms. This review article gives an overview of the actual situation. The genetic changes leading to malignancy are successively considered at the DNA, RNA and protein levels. Alterations at the DNA level represent the bulk of the available data, being related to p53 mutations, alterations in the beta-tubulin gene, microsatellite alterations, methods for identifying individual and isolated aberrant cells, identification of epigenetic mechanisms such as methylation of the promoter region of tumor suppressor genes; alterations in pre-neoplastic lesions are also evoked. In all cases, the techniques are described and results presented. RNA based methods are critically considered, and the yeast functional assay described. Protein based methods are also considered. The use of cDNA microarrays opens new perspectives and brings the simultaneous identification of numerous DNA alterations at a grip, with hopefully significant improvements in treatment results and increased efficiency for early detection and prevention.     

A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer

This study was carried out to assess, from the viewpoint of cost-effectiveness, the optimum number of faecal specimens to collect for use in immunochemical occult blood testing as a means of screening for colorectal cancer. 3300 asymptomatic individuals were subjects of this study. They gave samples for an immunochemical faecal occult blood test, monohaem and colonoscopy was carried out during a medical check-up. For evaluation of the optimum number of sampling specimens, the results of the first day of sampling, those of the first and second days, and those of samples taken for 3 consecutive days were considered as the single-day method, the 2-day method and the 3-day method respectively. The average cost to detect 1 patient with colorectal cancer, the detection rate and the false-positive rate of these three faecal sample collection methods were evaluated. The average costs for one cancer case detected were calculated as $3,630.68 for the single-day method, $3,350.65 for the 2-day method and $4,136.36 for the 3-day method, respectively. The detection rate and the false-positive rate were calculated as 47 and 3.5% for the single-day method, 82 and 4.7% for the 2-day method and 88 and 5.3% for the 3-day method, respectively. This detection rate was significantly different between the single- and the 2-day methods, as well as between the single- and the 3-day methods (P<0. 05). No significant differences in the false-positive rate amongst the three testing methods were observed. This analysis suggests that a 2-day faecal collection method is recommended for immunochemical occult blood screening by Monohaem from the aspects of cost-effectiveness and diagnostic accuracy.     

Occult blood screening for colorectal cancer

Because of the recent increase in the incidence of colorectal cancer in Japan, attempts were made to find an effective method for screening asymptomatic patients with this cancer. In current mass screening, guaiac-impregnated slides such as the Shionogi and Hemoccult types are widely used. A screening system consisting of examination with Shionogi B slides for 3 consecutive days under mild restricted diet and a medical questionnaire, followed by re-examination under a restricted diet for persons showing a partially positive result is accepted as the most reliable screening method. As these slide tests are based on peroxidase-like activity in hemoglobin, dietary fiber, meat, peroxidase-containing foods and drugs influence the sensitivity and specificity of the test. Recently, immunological fecal occult blood tests with high sensitivity and specificity such as RPHA or Feca-EIA have been developed. We have evaluated the RPHA method and compared it with the Shionogi B slide. The positive rate of the RPHA method was rather lower than that of the Shionogi test and the detection rate of Colorectal cancer was equivalent to that of Shionogi. We are now applying the RPHA method to mass screening, and the Feca-EIA Test is also under consideration for practical use.     

Facilitating factors for colorectal cancer screening

BACKGROUND: In this retrospective study, we examined factors that facilitated receipt of colorectal cancer (CRC) screening in a sample of low-income, predominantly African Americans participating in a tailored telephone education intervention. METHODS: A total of 61 individuals who received CRC screening were matched on age and sex with 61 individuals who had not received screening. Using records collected as part of the intervention, we identified facilitating factors and compared them between groups. RESULTS: We identified 8 facilitating factors, of which there were significant bivariate relationships with 6 factors. These 6 factors were stated familiarity with CRC test, seemed to only need reminder calls, seemed ready to screen, primary care physician (PCP) encouraged CRC screening, had an upcoming PCP appointment, and being prevention oriented. CONCLUSIONS: Identifying facilitating factors in those who receive screening may lead to insights about what factors need to be cultivated in those who do not receive screening.