Improved fecal DNA test for colorectal cancer screening

Stool DNA testing to screen for colorectal cancer in the Medicare population: a cost-effectiveness analysis

BACKGROUND

The Centers for Medicare & Medicaid Services considered whether to reimburse stool DNA testing for colorectal cancer screening among Medicare enrollees.

OBJECTIVE

To evaluate the conditions under which stool DNA testing could be cost-effective compared with the colorectal cancer screening tests currently reimbursed by the Centers for Medicare & Medicaid Services.

DESIGN

Comparative microsimulation modeling study using 2 independently developed models.

DATA SOURCES

Derived from literature.

TARGET POPULATION

A cohort of persons aged 65 years. A sensitivity analysis was also conducted, in which a cohort of persons aged 50 years was studied.

TIME HORIZON

Lifetime.

PERSPECTIVE

Third-party payer.

INTERVENTION

Stool DNA test every 3 or 5 years in comparison with currently recommended colorectal cancer screening strategies.

OUTCOME MEASURES

Life expectancy, lifetime costs, incremental cost-effectiveness ratios, and threshold costs.

RESULTS OF BASE-CASE ANALYSIS

Assuming a cost of $350 per test, strategies of stool DNA testing every 3 or 5 years yielded fewer life-years and higher costs than the currently recommended colorectal cancer screening strategies. Screening with the stool DNA test would be cost-effective at a per-test cost of $40 to $60 for stool DNA testing every 3 years, depending on the simulation model used. There were no levels of sensitivity and specificity for which stool DNA testing would be cost-effective at its current cost of $350 per test. Stool DNA testing every 3 years would be cost-effective at a cost of $350 per test if the relative adherence to stool DNA testing were at least 50% better than that with other screening tests.

RESULTS OF SENSITIVITY ANALYSIS

None of the results changed substantially when a cohort of persons aged 50 years was considered.

LIMITATION

No pathways other than the traditional adenoma-carcinoma sequence were modeled.

CONCLUSION

Stool DNA testing could be a cost-effective alternative for colorectal cancer screening if the cost of the test substantially decreased or if its availability would entice a large fraction of otherwise unscreened persons to receive screening.

Stool DNA testing to screen for colorectal cancer in the Medicare population: a cost-effectiveness analysis

BACKGROUND

The Centers for Medicare & Medicaid Services considered whether to reimburse stool DNA testing for colorectal cancer screening among Medicare enrollees.

OBJECTIVE

To evaluate the conditions under which stool DNA testing could be cost-effective compared with the colorectal cancer screening tests currently reimbursed by the Centers for Medicare & Medicaid Services.

DESIGN

Comparative microsimulation modeling study using 2 independently developed models.

DATA SOURCES

Derived from literature.

TARGET POPULATION

A cohort of persons aged 65 years. A sensitivity analysis was also conducted, in which a cohort of persons aged 50 years was studied.

TIME HORIZON

Lifetime.

PERSPECTIVE

Third-party payer.

INTERVENTION

Stool DNA test every 3 or 5 years in comparison with currently recommended colorectal cancer screening strategies.

OUTCOME MEASURES

Life expectancy, lifetime costs, incremental cost-effectiveness ratios, and threshold costs.

RESULTS OF BASE-CASE ANALYSIS

Assuming a cost of $350 per test, strategies of stool DNA testing every 3 or 5 years yielded fewer life-years and higher costs than the currently recommended colorectal cancer screening strategies. Screening with the stool DNA test would be cost-effective at a per-test cost of $40 to $60 for stool DNA testing every 3 years, depending on the simulation model used. There were no levels of sensitivity and specificity for which stool DNA testing would be cost-effective at its current cost of $350 per test. Stool DNA testing every 3 years would be cost-effective at a cost of $350 per test if the relative adherence to stool DNA testing were at least 50% better than that with other screening tests.

RESULTS OF SENSITIVITY ANALYSIS

None of the results changed substantially when a cohort of persons aged 50 years was considered.

LIMITATION

No pathways other than the traditional adenoma-carcinoma sequence were modeled.

CONCLUSION

Stool DNA testing could be a cost-effective alternative for colorectal cancer screening if the cost of the test substantially decreased or if its availability would entice a large fraction of otherwise unscreened persons to receive screening.

Molecular markers for early detection

A common belief is that the earlier that cancer is detected, the better the chance exists for reduced mortality and morbidity. The advent of new and emerging molecular, genetic, and imaging technologies has broadened the possible strategies for early detection and prevention, but a beneficial impact on mortality needs to be supported by clinical evidence. Molecular markers are being identified that are enhancing our ability to predict and detect cancer before it develops and at the earliest signs of impending carcinogenic transformation. Of the innumerable molecular markers in development, a standalone early detection marker with acceptable sensitivity and specificity is available for bladder cancer, although for most cancer sites there are promising avenues of research that will likely produce results in the next decade. The perfect molecular marker would be one that is inherently related to the disease, specifically to the processes of malignant tumorigenesis or to the defense mechanisms of the individual. For example, mutations associated with increased cancer risk often produce gene products that interfere with tumor-suppressor pathways (eg, DNA repair or cell-cycle control) or support oncogenic pathways (eg, through genetic instability or silencing the apoptotic pathway). Finding molecular markers associated with these processes, and where in the process they produce their actions, can lead to interventions based on maintaining support for the normal process and interrupting the action of the products of the mutation. The search for molecular markers for cancer prevention and early detection presents a formidable challenge that requires a systematic and scientifically sound validation process. The search encompasses a broad range of scientific disciplines, including biochemistry, genetics, histology, immunology, informatic technologies, and epidemiology; strategies to identify and understand molecular markers are approached with multidisciplinary teams focused on understanding the mechanistic basis of cancer and the processes and pathways that underlie carcinogenesis.

Performance improvements of stool-based screening tests

Stool testing is a widely accepted, non-invasive, technique for colorectal cancer (CRC) screening. Guaiac-based faecal occult blood test (gFOBT) screening has been proven to decrease CRC-related mortality; however gFOBT is hampered by a low sensitivity. Faecal immunochemical tests (FITs) have several advantages over gFOBT. First of all, FIT has a better sensitivity and higher uptake. Furthermore, the quantitative variant of the FIT allows choices on cut-off level for test-positivity according to colonoscopy resources available, personal risk profile, and/or intended detection rate in the screened population. Stool-based DNA (sDNA) tests aiming at the detection of specific DNA alterations may improve detection of CRC and adenomas compared to gFOBT screening, but large-scale population based studies are lacking. This review focuses on factors influencing test performance of those three stool based screening tests.

Stool studies: tried, true, and new

Much information can be obtained about a patient's gastrointestinal and overall nutritional status through stool samples. Important infectious processes and neoplastic processes are initially identified through diagnostic tests and screening of stool samples. Although in some arenas they are a source of embarrassment and distaste, the value of correctly obtained samples is unquestionable. Patient collaboration with a critical care nurse is integral to obtaining stool samples.

Molecular detection of colorectal neoplasia

A variety of noninvasive molecular approaches to colorectal cancer screening are emerging with potential to improve screening effectiveness and user-friendliness. These approaches are based on the sensitive assay of molecular markers in stool, blood, and urine samples. New methods, especially next generation stool-based tests, have been shown to detect both colorectal cancers and precancerous lesions with high accuracy. Validation of these technologies in average-risk populations are needed to establish their role for general colorectal cancer screening. This review addresses the biological rationale, technical advances, recent clinical performance data, and remaining issues with molecular screening for colorectal cancer.

DNA methylation markers in colorectal cancer

Colorectal cancer (CRC) arises as a consequence of the accumulation of genetic and epigenetic alterations in colonic epithelial cells during neoplastic transformation. Epigenetic modifications, particularly DNA methylation in selected gene promoters, are recognized as common molecular alterations in human tumors. Substantial efforts have been made to determine the cause and role of aberrant DNA methylation ("epigenomic instability") in colon carcinogenesis. In the colon, aberrant DNA methylation arises in tumor-adjacent, normal-appearing mucosa. Aberrant methylation also contributes to later stages of colon carcinogenesis through simultaneous methylation in key specific genes that alter specific oncogenic pathways. Hypermethylation of several gene clusters has been termed CpG island methylator phenotype and appears to define a subgroup of colon cancer distinctly characterized by pathological, clinical, and molecular features. DNA methylation of multiple promoters may serve as a biomarker for early detection in stool and blood DNA and as a tool for monitoring patients with CRC. DNA methylation patterns may also be predictors of metastatic or aggressive CRC. Therefore, the aim of this review is to understand DNA methylation as a driving force in colorectal neoplasia and its emerging value as a molecular marker in the clinic.

Sources of bias in specimens for research about molecular markers for cancer

Claims about the diagnostic or prognostic accuracy of markers often prove disappointing when "discrimination" found between cancers versus normals is due to bias, a systematic difference between compared groups. This article describes a framework to help simplify and organize current problems in marker research by focusing on the role of specimens as a source of bias in observational research and using that focus to address problems and improve reliability. The central idea is that the "fundamental comparison" in research about markers (ie, the comparison done to assess whether a marker discriminates) involves two distinct processes that are "connected" by specimens. If subject selection (first process) creates baseline inequality between groups being compared, then laboratory analysis of specimens (second process) may erroneously find positive results. Although both processes are important, subject selection more fundamentally influences the quality of marker research, because it can hardwire bias into all comparisons in a way that cannot be corrected by any refinement in laboratory analysis. An appreciation of the separateness of these two processes-and placing investigators with appropriate expertise in charge of each-may increase the reliability of research about cancer biomarkers.

Advances in colorectal cancer screening

Colorectal cancer (CRC) remains the third most commonly diagnosed cancer and second leading cause of cancer death in the United States. Declines in CRC incidence and mortality over the past 20 years were attributed to CRC screening. Yet, only slightly more than half of the eligible at-risk population acknowledge being screened. To effectively meet the demands of screening in an enlarging, ethnically diverse, and aging population, a variety of modalities are needed. This article provides a focused assessment of effectiveness, limitations, and alternative available screening methods. New modalities endorsed in the updated guidelines (eg, fecal immunochemical tests, fecal DNA, and CT colonography) are reviewed. In addition, advances and updates in existing tests (eg, guaiac-based fecal occult blood tests and colonoscopy) are evaluated.

DNA/RNA markers for colorectal cancer risk in preserved stool specimens: a pilot study

AIMS AND BACKGROUND

Exfoliated cells in human stool offer excellent opportunities to non-invasively detect molecular markers associated with colorectal tumorigenesis, and to evaluate the effects of exposures to exogenous and endogenous carcinogenic or chemopreventive substances. This pilot study investigated the feasibility of determining DNA methylation and RNA expression simultaneously in stool specimens treated with a single type of nucleic acid preservatives.

METHODS

Stool specimens from 56 volunteers that were preserved up to a week with RNA later were used in this study. Bisulfite sequencing was used to determine methylation at 27 CpG loci on the estrogen receptor 1 (ESR1) promoter. Taqman assay was used for quantitative reverse transcription polymerase chain reactions to measure cyclooxygenase 2 (COX2) and epidermal growth factor receptor (EGFR) mRNA expression. Subjects' basic demographic and other selected risk factors for colorectal cancer were captured through questionnaires and correlated with the levels of these markers.

RESULTS

Less than 10% of the samples failed in individual assays. Overall, 24.0% of the CpG loci on the ESR1 promoter were methylated. COX2 expression and alcohol use were positively correlated; an inverse association was present between EGFR expression and cigarette smoking; and subjects using anti-diabetic medication had higher ESR1 methylation. In addition, higher EGFR expression levels were marginally associated with history of polyps and family history of colorectal cancer.

CONCLUSIONS

The present study demonstrates that simultaneous analyses for DNA and RNA markers are feasible in stool samples treated with a single type of nucleotide preservatives. Among several associations observed, the association between EGFR expression and polyps deserves further investigation as a potential target for colorectal cancer screening. Larger studies are warranted to confirm some of our observations.

Simultaneous Detection of Colorectal Cancer Mutations in Stool Samples with Biochip Arrays

Colorectal cancer (CRC) is the second main cause of cancer-related death in the Western world and like many other tumours is curable if detected at an early stage. Current detection options include faecal occult blood testing and invasive direct visualisation techniques such as flexible sigmoidoscopy, colonoscopy and barium enema. The availability of a more simple, non-invasive test that detects tumour specific products with optimal analytical performance might overcome barriers among patients who are not willing to undergo more sensitive but invasive tests. One such emerging technology, which has shown promise in recent years, is the analysis of DNA alterations exfoliated from tumour cells into stool. Here we report an analytical platform for non-invasive detection of 28 common mutations within CRC-related genesAPC, TP53, K-rasandBRAFin stool samples based on biochip array technology and applied to the semi-automated Evidence Investigator analyser. Mutation detection was possible in 1000-fold excess of wildtype DNA and analysis of 10 CRC-positive patient samples showed presence of targeted mutations with equivalent mutations also identified by an alternative method. This application represents an excellent tool for the multiplex detection of CRC-specific mutations using a single platform.

Colon cancer screening and surveillance controversies

PURPOSE OF REVIEW

To discuss new colorectal cancer screening tests and highlight controversies regarding colon screening and surveillance.

RECENT FINDINGS

New screening guidelines were published in 2008. Tests that primarily detect early cancer include sensitive guaiac fecal occult blood test or fecal immunochemical test. Tests that can detect both early cancer and cancer precursor lesions include sigmoidoscopy and colonoscopy. One guideline endorses the use of computed tomographic colonography. Limitations of each test are highlighted in the new guidelines. Controversies include age to start screening, age to stop screening, and appropriate interval after a negative screening colonoscopy. New work has raised some doubt about the protective effect of colonoscopy in the proximal colon. Finally, there is new emphasis on the quality of screening programs.

SUMMARY

Colorectal cancer screening can reduce both incidence and mortality of colorectal cancer if performed with high quality. New work should focus on improving the quality of all screening programs.

Analysis of fecal DNA methylation to detect gastrointestinal neoplasia

BACKGROUND

The development of noninvasive screening tests is important to reduce mortality from gastrointestinal neoplasia. We sought to develop such a test by analysis of DNA methylation from exfoliated cancer cells in feces.

METHODS

We first analyzed methylation of the RASSF2 and SFRP2 gene promoters from 788 primary gastric and colorectal tissue specimens to determine whether methylation patterns could act as stage-dependent biomarkers of gastrointestinal tumorigenesis. Next, we developed a novel strategy that uses single-step modification of DNA with sodium bisulfite and fluorescence polymerase chain reaction methodology to measure aberrant methylation in fecal DNA. Methylation of the RASSF2 and SFRP2 promoters was analyzed in 296 fecal samples obtained from a variety of patients, including 21 with gastric tumors, 152 with colorectal tumors, and 10 with non-neoplastic or inflammatory lesions in the gastrointestinal lumen.

RESULTS

Analysis of DNA from tissues showed presence of extensive methylation in both gene promoters exclusively in advanced gastric and colorectal tumors. The assay successfully identified one or more methylated markers in fecal DNA from 57.1% of patients with gastric cancer, 75.0% of patients with colorectal cancer, and 44.4% of patients with advanced colorectal adenomas, but only 10.6% of subjects without neoplastic or active diseases (difference, gastric cancer vs undiseased = 46.5%, 95% confidence interval (CI) = 24.6% to 68.4%, P < .001; difference, colorectal cancer vs undiseased = 64.4%, 95% CI = 53.5% to 75.2%, P < .001; difference, colorectal adenoma vs undiseased = 33.8%, 95% CI = 14.2% to 53.4%, P < .001).

CONCLUSIONS

Methylation of the RASSF2 and SFRP2 promoters in fecal DNA is associated with the presence of gastrointestinal tumors relative to non-neoplastic conditions. Our novel fecal DNA methylation assay provides a possible means to noninvasively screen not only for colorectal tumors but also for gastric tumors.

Genetic and epigenetic marker-based DNA test of stool is a promising approach for colorectal cancer screening

Colorectal cancer (CRC) is one of the most common malignancies and leading cause of cancer-related deaths in the world.1 However, it may be treated effectively by surgical removal of the cancerous tissue if detected at early stages. Conventional tools for screening CRC are either invasive or inaccurate. Therefore, there is an urgent need to develop a reliable screening tools for CRC to significantly reduce its morbidity. In this regard, a novel DNA markers-based detection in stool is emerging as a promising approach.

Comparative analysis of PCR-based biomarker assay methods for colorectal polyp detection from fecal DNA

BACKGROUND

Aberrantly methylated genes are promising biomarkers for the detection of colon adenomas and colorectal cancers (CRCs). The optimal assay type and specific methylated genes for these assays remain to be determined.

METHODS

We used genomewide microarray-based assays to identify methylated genes as candidate biomarkers for colon neoplasms. The frequency of aberrant methylation of these genes in primary tumors was assessed with methylation-specific PCR (MSP). The limits of detection and specificities for different types of PCR-based assays were then assessed with the most promising genes identified in this screen. Finally, we assessed the best-performing MSP assay as an early-detection marker using fecal DNA samples.

RESULTS

ITGA4 [integrin, alpha 4 (antigen CD49D, alpha 4 subunit of VLA-4 receptor)] was identified as a novel gene frequently methylated in CRC. Methylated ITGA4 is present in 75% of colon adenomas (n = 36) and 92% of colon adenocarcinomas (n = 75). Comparison of end point MSP, end point MSP with clamped primers, and quantitative fluorescent MSP (qMSP) approaches revealed that both types of end point MSP assays could routinely detect as little as 70 pg DNA, whereas the qMSP assay could routinely detect as little as 7 pg. A fecal DNA qMSP assay for methylated ITGA4 can detect 69% of individuals with colon adenomas (n = 13) with a diagnostic specificity of 79% (n = 28).

CONCLUSIONS

Methylated ITGA4 is a promising marker gene for the early detection of colonic neoplasms. qMSP has the lowest limit of detection of the MSP assay types tested, and a qMSP assay that detects methylated ITGA4 has potential as an early-detection assay for colon neoplasms.

N-Myc downstream-regulated gene 4 (NDRG4): a candidate tumor suppressor gene and potential biomarker for colorectal cancer

BACKGROUND

Identification of hypermethylated tumor suppressor genes in body fluids is an appealing strategy for the noninvasive detection of colorectal cancer. Here we examined the role of N-Myc downstream-regulated gene 4 (NDRG4) as a novel tumor suppressor and biomarker in colorectal cancer.

METHODS

NDRG4 promoter methylation was analyzed in human colorectal cancer cell lines, colorectal tissue, and noncancerous colon mucosa by using methylation-specific polymerase chain reaction (PCR) and bisulfite sequencing. NDRG4 mRNA and protein expression were studied using real-time-PCR and immunohistochemistry, respectively. Tumor suppressor functions of NDRG4 were examined by colony formation, cell proliferation, and migration and invasion assays in colorectal cancer cell lines that were stably transfected with an NDRG4 expression construct. Quantitative methylation-specific PCR was used to examine the utility of NDRG4 promoter methylation as a biomarker in fecal DNA from 75 colorectal cancer patients and 75 control subjects. All P values are two-sided.

RESULTS

The prevalence of NDRG4 promoter methylation in two independent series of colorectal cancers was 86% (71/83) and 70% (128/184) compared with 4% (2/48) in noncancerous colon mucosa (P < .001). NDRG4 mRNA and protein expression were decreased in colorectal cancer tissue compared with noncancerous colon mucosa. NDRG4 overexpression in colorectal cancer cell lines suppressed colony formation (P = .014), cell proliferation (P < .001), and invasion (P < .001). NDRG4 promoter methylation analysis in fecal DNA from a training set of colorectal cancer patients and control subjects yielded a sensitivity of 61% (95% confidence interval [CI] = 43% to 79%) and a specificity of 93% (95% CI = 90% to 97%). An independent test set of colorectal cancer patients and control subjects yielded a sensitivity of 53% (95% CI = 39% to 67%) and a specificity of 100% (95% CI = 86% to 100%).

CONCLUSIONS

NDRG4 is a candidate tumor suppressor gene in colorectal cancer whose expression is frequently inactivated by promoter methylation. NDRG4 promoter methylation is a potential biomarker for the noninvasive detection of colorectal cancer in stool samples.

Sensitive and specific detection of early gastric cancer with DNA methylation analysis of gastric washes

BACKGROUND & AIMS

Aberrant DNA methylation is an early and frequent process in gastric carcinogenesis and could be useful for detection of gastric neoplasia. We hypothesized that methylation analysis of DNA recovered from gastric washes could be used to detect gastric cancer.

METHODS

We studied 51 candidate genes in 7 gastric cancer cell lines and 24 samples (training set) and identified 6 for further studies. We examined the methylation status of these genes in a test set consisting of 131 gastric neoplasias at various stages. Finally, we validated the 6 candidate genes in a different population of 40 primary gastric cancer samples and 113 nonneoplastic gastric mucosa samples.

RESULTS

Six genes (MINT25, RORA, GDNF, ADAM23, PRDM5, MLF1) showed frequent differential methylation between gastric cancer and normal mucosa in the training, test, and validation sets. GDNF and MINT25 were most sensitive molecular markers of early stage gastric cancer, whereas PRDM5 and MLF1 were markers of a field defect. There was a close correlation (r = 0.5-0.9, P = .03-.001) between methylation levels in tumor biopsy and gastric washes. MINT25 methylation had the best sensitivity (90%), specificity (96%), and area under the receiver operating characteristic curve (0.961) in terms of tumor detection in gastric washes.

CONCLUSIONS

These findings suggest MINT25 is a sensitive and specific marker for screening in gastric cancer. Additionally, we have developed a new method for gastric cancer detection by DNA methylation in gastric washes.

Noninvasive detection of candidate molecular biomarkers in subjects with a history of insulin resistance and colorectal adenomas

We have developed novel molecular methods using a stool sample, which contains intact sloughed colon cells, to quantify colonic gene expression profiles. In this study, our goal was to identify diagnostic gene sets (combinations) for the noninvasive classification of different phenotypes. For this purpose, the effects of a legume-enriched, low glycemic index, high fermentable fiber diet was evaluated in subjects with four possible combinations of risk factors, including insulin resistance and a history of adenomatous polyps. In a randomized crossover design controlled feeding study, each participant (a total of 23; 5-12 per group) consumed the experimental diet (1.5 cups of cooked dry beans) and a control diet (isocaloric average American diet) for 4 weeks with a 3-week washout period between diets. Using prior biological knowledge, the complexity of feature selection was reduced to perform an exhaustive search on all allowable feature (gene) sets of size 3, and among these, 27 had (unbiased) error estimates of 0.15 or less. Linear discriminant analysis was successfully used to identify the best single genes and two- to three-gene combinations for distinguishing subjects with insulin resistance, a history of polyps, or exposure to a chemoprotective legume-rich diet. These results support our premise that gene products (RNA) isolated from stool have diagnostic value in terms of assessing colon cancer risk.

[Colorectal cancer screening programme in France, role of the National Institute of Cancer]

With almost 37,500 new cases per year and 17,000 deaths, colorectal cancer represents a major public health problem in France. A new stage in the fight against this cancer should be marked in 2009 with the widespread implementation of the colorectal cancer screening programme over the whole of the French territory. This population-based screening programme targets an eligible population of 16 million persons. The evaluation of the first 23 pilot districts allowed a standardization of the main quality and efficacy indicators. The implementation of the colorectal cancer screening programme relies on monitoring centres, usually one per district, set up for the national breast cancer screening programme. The programme refers to quality assurance guidelines and includes explicit policy with specified age categories, method, and interval for screening. A national screening training programme for newly districts joining the programme was implemented. A small number of laboratories have been selected for the programme on quality criteria. The French National Cancer Institute contributes to organization, information, guidelines, and research. The replacement of the guaiac test used in the French programme by an immunochemical test should be effective in the next few years.

American College of Gastroenterology guidelines for colorectal cancer screening 2009 [corrected]

This document is the first update of the American College of Gastroenterology (ACG) colorectal cancer (CRC) screening recommendations since 2000. The CRC screening tests are now grouped into cancer prevention tests and cancer detection tests. Colonoscopy every 10 years, beginning at age 50, remains the preferred CRC screening strategy. It is recognized that colonoscopy is not available in every clinical setting because of economic limitations. It is also realized that not all eligible persons are willing to undergo colonoscopy for screening purposes. In these cases, patients should be offered an alternative CRC prevention test (flexible sigmoidoscopy every 5-10 years, or a computed tomography (CT) colonography every 5 years) or a cancer detection test (fecal immunochemical test for blood, FIT).

Stool testing for the early detection of pancreatic cancer: rationale and current evidence

The development of effective tools for the early detection of pancreatic cancer, or its precursors, in high-risk subjects could play a key role in reducing the burden of this disease, which is the most lethal among solid gastrointestinal tumors. Given the poor accessibility of the pancreas due to its anatomic site, and given the limitations of imaging modalities, biomarker screening might be a promising diagnostic option. This review focuses on the rationale of using stool markers for the early detection of pancreatic cancer, and systematically summarizes current evidence. Despite several potential advantages of stool testing for pancreatic cancer and its biological plausibility, only six studies investigating two genetic markers in stool (the K-ras and the p53 gene) could be identified. Even though these studies were limited in size and could hardly approximate the screening setting, both markers appear to lack sensitivity and, in particular, specificity. The investigation of further marker candidates (e.g., epigenetic markers) in adequately designed studies represents an important next step to explore the potential of stool testing for pancreatic cancer. Pertinent studies could greatly benefit from recent methodological advances gained in connection with stool testing for colorectal cancer.

Colon cancer and the elderly: from screening to treatment in management of GI disease in the elderly

Colorectal cancer is one of the commonest tumours in the Westernized world affecting mainly the elderly. This neoplasm in older individuals occurs more often in the right colon and grows more rapidly than in the young, often shows a mucinous histology and mismatch repair gene changes. Effective screening permits discovery of colorectal cancer at an early highly treatable stage and allows for detection and removal of premalignant colorectal adenomas. Screening methods that focus on cancer detection use fecal assays for the presence of blood or altered DNA, those for detection of adenomas (and early cancer) use endoscopic or computerised radiologic techniques. Broad use of screening methods has lowered colorectal cancer development by about 50%. In addition, prevention of the earliest stage of colon carcinogenesis has been shown to be effective in small prospective studies and epidemiologic surveys but have not been employed in the general population. Since 1996 the chemotherapeutic armamentarium for metastatic colorectal cancer has grown beyond 5-fluorouracil to include an oral 5-fluorouracil prodrug, capecitabine as well as irinotecan and oxaliplatin. Three targeted monoclonal antibodies (Moabs), bevacizumab (an anti-vascular endothelial growth factor Moab) and cetuximab/panitumumab, both anti-epidermal growth factor receptor inhibitors, have also earned regulatory approval. Most stage IV patients are treated with all of these drugs over 2 or 3 sequential lines of palliative chemotherapy and attain median survivals approaching 24 months. Lastly, adjuvant oxaliplatin plus 5-fluorouracil for high risk resected stage II and stage III colon cancer patient has led to substantial improvement in cure rates. With appropriate care of age associated comorbidities these treatment modalities are feasible and effective in the geriatric population.

Detection of the DNA point mutation of colorectal cancer cells isolated from feces stored under different conditions

BACKGROUND

We reported on a novel diagnostic method for colorectal cancer (CRC) using a DNA-based analysis of isolated colonocytes from feces. The aim of the present study was to investigate with real-time PCR and direct sequencing analysis whether the cancer cells could be detected in feces stored under different conditions after evacuation.

METHODS

Feces were collected from patients with CRC. Feces were divided into 21 pieces and each piece was manipulated at time after arrival (zero time) and after storage of 24, 48 and 72 h at 4 or 37 degrees C. Colonocytes were isolated from each separate fecal sample, and DNA and RNA were extracted from the colonocytes. We investigated the relationship between storage conditions and content of extracted DNA or RNA with real-time PCR. We also clarified the gene alterations regarding APC and p53 genes under different storage conditions with direct sequence analysis.

RESULTS

Though the amount of genomic DNA and total RNA recovered from colonocytes isolated from each fecal piece decreased significantly at 37 degrees C at any storage time compared with 0 h, the gene alterations were detected independent of any storage conditions.

CONCLUSIONS

The colonocytes recovery rate from feces was unchanging for 3 days as long as the feces were kept at 4 degrees C. However, the identical point mutation to one obtained in cancer tissue was detected in the corresponding exfoliated colonocytes even after storage for 72 h at 37 degrees C, which suggests that exfoliated CRC cells maintain their configuration in feces at least 3 days after evacuation.

A simplified, noninvasive stool DNA test for colorectal cancer detection

BACKGROUND

As a noninvasive colorectal cancer (CRC) screening test, a multi-marker first generation stool DNA (sDNA V 1.0) test is superior to guaiac-based fecal occult blood tests. An improved sDNA assay (version 2), utilizing only two markers, hypermethylated vimentin gene (hV) and a two site DNA integrity assay (DY), demonstrated in a training set (phase 1a) an even higher sensitivity (88%) for CRC with a specificity of 82%.

AIM

To validate in an independent set of patients (phase 1b) the sensitivity and specificity of sDNA version 2 for CRC.

METHODS

Forty-two patients with CRC and 241 subjects with normal colonoscopy (NC) provided stool samples, to which they immediately added DNA stabilizing buffer, and mailed their specimen to the laboratory. DNA was purified using gel-based capture, and analyzed for hV and DY using methods identical to those previously published.

RESULTS

Using the same cutpoints as the 1a training set (N = 162; 40 CRCs, 122 normals), hV demonstrated a higher and DY a slightly lower sensitivity, for a combined sensitivity of hV + DY of 86%. Optimal cutpoints based on the combined phase 1a + 1b dataset (N = 445; 82 CRCs, 363 normals) yielded a CRC sensitivity of 83%. The vast majority of cancers were detected regardless of tumor stage, tumor location, or patient age. Assay specificity in the phase 1b dataset for hV, DY, and hV + DY was 82%, 85%, and 73%, respectively, using the phase 1a cutpoints. Optimal cutpoints based on the combined phase 1a + 1b dataset yield a specificity of 82%.

CONCLUSIONS

This study provides validation of a simplified, improved sDNA test that incorporates only two markers and that demonstrates high sensitivity (83%) and specificity (82%) for CRC. Test performance is highly reproducible in a large set of patients. The use of only two markers will make the test easier to perform, reduce the cost, and facilitate distribution to local laboratories.

Stool DNA and occult blood testing for screen detection of colorectal neoplasia

BACKGROUND

Stool DNA testing is a new approach to colorectal cancer detection. Few data are available from the screening setting.

OBJECTIVE

To compare stool DNA and fecal blood testing for detection of screen-relevant neoplasia (curable-stage cancer, high-grade dysplasia, or adenomas >1 cm).

DESIGN

Blinded, multicenter, cross-sectional study.

SETTING

Communities surrounding 22 participating academic and regional health care systems in the United States.

PARTICIPANTS

4482 average-risk adults.

MEASUREMENTS

Fecal blood and DNA markers. Participants collected 3 stools, smeared fecal blood test cards and used same-day shipment to a central facility. Fecal blood cards (Hemoccult and HemoccultSensa, Beckman Coulter, Fullerton, California) were tested on 3 stools and DNA assays on 1 stool per patient. Stool DNA test 1 (SDT-1) was a precommercial 23-marker assay, and a novel test (SDT-2) targeted 3 broadly informative markers. The criterion standard was colonoscopy.

RESULTS

Sensitivity for screen-relevant neoplasms was 20% by SDT-1, 11% by Hemoccult (P = 0.020), 21% by HemoccultSensa (P = 0.80); sensitivity for cancer plus high-grade dysplasia did not differ among tests. Specificity was 96% by SDT-1, compared with 98% by Hemoccult (P < 0.001) and 97% by HemoccultSensa (P = 0.20). Stool DNA test 2 detected 46% of screen-relevant neoplasms, compared with 16% by Hemoccult (P < 0.001) and 24% by HemoccultSensa (P < 0.001). Stool DNA test 2 detected 46% of adenomas 1 cm or larger, compared with 10% by Hemoccult (P < 0.001) and 17% by HemoccultSensa (P < 0.001). Among colonoscopically normal patients, the positivity rate was 16% with SDT-2, compared with 4% with Hemoccult (P = 0.010) and 5% with HemoccultSensa (P = 0.030).

LIMITATIONS

Stool DNA test 2 was not performed on all subsets of patients without screen-relevant neoplasms. Stools were collected without preservative, which reduced detection of some DNA markers.

CONCLUSION

Stool DNA test 1 provides no improvement over HemoccultSensa for detection of screen-relevant neoplasms. Stool DNA test 2 detects significantly more neoplasms than does Hemoccult or HemoccultSensa, but with more positive results in colonoscopically normal patients. Higher sensitivity of SDT-2 was particularly apparent for adenomas.

Improved diagnosis of colorectal cancer using a combination of fecal occult blood and novel fecal protein markers

BACKGROUND & AIMS

Annual testing for fecal occult blood is recommended as first-line screening for the detection of colorectal cancer (CRC), but is affected by limited sensitivity. We initiated a proteomics-based search for novel biomarkers to improve the sensitivity of detection of CRC in stool samples.

METHODS

Six markers, including immunologic fecal occult blood test (iFOBT), were evaluated in a collective of 551 samples (186 CRC, 113 advanced adenoma, and 252 control patients) to establish the diagnostic performance of each marker and marker combinations.

RESULTS

We tested the known stool markers hemoglobin (iFOBT), hemoglobin-haptoglobin, calprotectin, carcinoembryogenic antigen, and the novel fecal markers tissue inhibitor of metalloproteinase-1 (TIMP-1) and S100A12. The best diagnostic performance was found for S100A12 with an area under the curve of 0.95, followed by TIMP-1 (0.92), hemoglobin-haptoglobin (0.92), hemoglobin (0.91), calprotectin (0.90), and carcinoembryogenic antigen (0.66). By using Bayes logistic regression as a mathematic model, the highest sensitivity (88%) for the detection of CRC at 95% specificity was obtained with the marker pair S100A12 and hemoglobin-haptoglobin. Increasing the specificity to 98%, the combination of S100A12, hemoglobin-haptoglobin, and TIMP-1 resulted in a sensitivity of 82%, with the highest increase of sensitivity found in early tumor stages (international union against cancer stage I: 74% sensitivity vs 57% of the best single marker).

CONCLUSIONS

Depending on the specificity selected, a marker pair, S100A12 and hemoglobin-haptoglobin, or a triple combination including TIMP-1, allowed the detection of CRC at significantly higher rates than can be obtained with iFOBT alone.

Detection of colorectal cancer cells from feces using quantitative real-time RT-PCR for colorectal cancer diagnosis

Early detection of colorectal cancer (CRC) is desired for reducing its mortality rate. Recently, the feasibility of a new method for isolating colonocytes from feces was demonstrated, followed by direct sequencing analysis for detecting colorectal cancer. In the present study, gene expression analysis was conducted using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). One hundred and sixty-six patients with CRC and 134 healthy volunteers were enrolled. Messenger RNA expressions of CEA, MMP7, MYBL2, PTGS2 and TP53 in the colonocytes isolated from feces were analyzed by quantitative real-time RT-PCR. Beta-2-microglobulin, used for internal control, could not be detected in approximately 25% each of the CRC patients (39/166) and healthy volunteers (33/134). CEA expression did not differ significantly between CRC patients and healthy volunteers (P = 0.21). MMP7, MYBL2, PTGS2 and TP53 gene expressions were significantly higher in CRC patients than in healthy volunteers (P < 0.001). The overall sensitivity and specificity using these gene expressions were 58.3% (74/127, 95% CI; 49.2-67.0) and 88.1% (89/101, 95% CI; 80.2-93.7), respectively. The sensitivity was dependent on the tumor location (P = 0.01) and tumor size (P = 0.02), but not the tumor depth (P = 0.06) or cancer stage (P = 0.37). Gene expression analysis of colonocytes isolated from feces may be a useful method for CRC screening, if the number of isolated colonocytes is sufficiently high for analysis by quantitative real-time PCR. Therefore, improvement of the colonocyte retrieval system from feces may be necessary for the technique to be developed for clinical use.

Colorectal cancer in inflammatory bowel disease

Patients with long-standing inflammatory bowel disease have an increased risk of developing colorectal cancer (CRC). CRC risk increases with longer duration of colitis, greater anatomic extent of colitis, the presence of primary sclerosing cholangitis, family history of CRC and severity of inflammation of the colon. Chemoprevention includes aminosalicylates, ursodeoxycholic acid, and possibly folic acid. To reduce CRC mortality in IBD, colonoscopic surveillance remains the major way to detect early mucosal dysplasia. When dysplasia is confirmed, proctocolectomy is considered for these patients. Ulcerative colitis patients with total proctocolectomy and ileal pouch anal-anastomosis have a rather low risk of dysplasia in the ileal pouch, but the anal transition zone should be monitored periodically. New endoscopic and molecular screening approaches may further refine our current surveillance guidelines and our understanding of the natural history of dysplasia.

Analysis of mutations in DNA isolated from plasma and stool of colorectal cancer patients

BACKGROUND & AIMS

Somatic mutations provide uniquely specific markers for the early detection of neoplasia that can be detected in DNA purified from plasma or stool of patients with colorectal cancer. The primary purpose of the present investigation was to determine the parameters that were critical for detecting mutations using a quantitative assay. A secondary purpose was to compare the results of plasma and stool DNA testing using the same technology.

METHODS

We examined DNA purified from the stool of 25 patients with colorectal cancers before surgery. In 16 of these cases, plasma samples also were available. Mutations in stool or plasma were assessed with an improved version of the BEAMing technology.

RESULTS

Of the 25 stool DNA samples analyzed, 23 (92%) contained mutations that were present in the corresponding tumors from the same patients. In contrast, only 8 of the 16 (50%) plasma DNA samples analyzed had detectable levels of mutated DNA. We found that the DNA fragments containing mutations in both stool and plasma DNA typically were smaller than 150 bases in size. The sensitivity of the new method was superior to a widely used technique for detecting mutations, using single base extension and sequencing, when assessed on the same samples (92% vs 60%; P = .008, exact McNemar test).

CONCLUSIONS

When assessed with sufficiently sensitive methods, mutant DNA fragments are detectable in the stool of more than 90% of colorectal cancer patients. DNA purified from stool provides a better template for mutation testing than plasma.

Fecal DNA screening in colorectal cancer

Colorectal cancer (CRC) is the third most common type of cancer diagnosed in Canada, and is the leading cause of cancer-related deaths in nonsmokers. Although CRC is considered to be 90% curable if detected early, the majority of patients present with advanced stage III or IV disease. An effective screening test may significantly decrease disease burden. The present paper examines the rationale and potential of fecal DNA testing as an alternative and adjunct to other CRC screening tests. The most efficacious fecal DNA test developed to date has a sensitivity and specificity of 87.5% and 82%, respectively. The approach has a higher positive predictive value than the currently used fecal occult blood test and offers a noninvasive option to patients. It is not reliant on the presence of bleeding, which may be intermittent or altogether absent. The test is now commercially available and is supported by a number of American insurers. Current challenges include cost reduction and demonstration of mortality benefit in a rigorous clinical trial. Despite current challenges, fecal DNA testing is worth pursuing. Both the American Gastroenterological Society and the American Cancer Society maintain that molecular testing is in its infancy but is promising. Fecal DNA testing has the potential to be an exciting addition to the current armament of CRC screening options.

Screening, surveillance, and prevention of colorectal cancer

Colon cancer screening can be effective, but only with a high-quality program that assures adherence to all elements of the program. There is evidence in the United States of greater acceptance of screening and decreased incidence and mortality of colorectal cancer. Patient education is a key element of any effective screening program. It is hoped that future screening will develop better risk-stratification tools and enable targeting of screening to high-risk individuals.

Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology

In the United States, colorectal cancer (CRC) is the third most common cancer diagnosed among men and women and the second leading cause of death from cancer. CRC largely can be prevented by the detection and removal of adenomatous polyps, and survival is significantly better when CRC is diagnosed while still localized. In 2006 to 2007, the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology came together to develop consensus guidelines for the detection of adenomatous polyps and CRC in asymptomatic average-risk adults. In this update of each organization's guidelines, screening tests are grouped into those that primarily detect cancer early and those that can detect cancer early and also can detect adenomatous polyps, thus providing a greater potential for prevention through polypectomy. When possible, clinicians should make patients aware of the full range of screening options, but at a minimum they should be prepared to offer patients a choice between a screening test that primarily is effective at early cancer detection and a screening test that is effective at both early cancer detection and cancer prevention through the detection and removal of polyps. It is the strong opinion of these 3 organizations that colon cancer prevention should be the primary goal of screening.

As tests evolve and costs of cancer care rise: reappraising stool-based screening for colorectal neoplasia

BACKGROUND

Colorectal cancer screening and treatment are rapidly evolving. Aims To reappraise stool-based colorectal cancer screening in light of changing test performance characteristics, lower test cost and increasing colorectal cancer care costs.

METHODS

Using a Markov model, we compared faecal DNA testing every 3 years, annual faecal occult blood testing or immunochemical testing, and colonoscopy every 10 years.

RESULTS

In the base case, faecal occult blood testing and faecal immunochemical testing gained life-years/person and cost less than no screening. Faecal DNA testing version 1.1 at $300 (the current PreGen Plus test) gained 5323 life-years/100 000 persons at $16 900/life-year gained and faecal DNA testing version 2 (enhanced test) gained 5795 life-years/100 000 persons at $15 700/life-year gained vs. no screening. In the base case and most sensitivity analyses, faecal occult blood testing and faecal immunochemical testing were preferred to faecal DNA testing. Faecal DNA testing version 2 cost $100 000/life-year gained vs. faecal immunochemical testing when per-cycle adherence with faecal immunochemical testing was 22%. Faecal immunochemical testing with excellent adherence was superior to colonoscopy every 10 years.

CONCLUSIONS

As novel biological therapies increase colorectal cancer treatment costs, faecal occult blood testing and faecal immunochemical testing could become cost-saving. The cost-effectiveness of faecal DNA testing compared with no screening has improved, but faecal occult blood testing and faecal immunochemical testing are preferred to faecal DNA testing when patient adherence is high. Faecal immunochemical testing may be comparable to colonoscopy every 10 years in persons adhering to yearly testing.

Hypermethylated MAL gene - a silent marker of early colon tumorigenesis

Background

Tumor-derived aberrantly methylated DNA might serve as diagnostic biomarkers for cancer, but so far, few such markers have been identified. The aim of the present study was to investigate the potential of the MAL (T-cell differentiation protein) gene as an early epigenetic diagnostic marker for colorectal tumors.

Methods

Using methylation-specific polymerase chain reaction (MSP) the promoter methylation status of MAL was analyzed in 218 samples, including normal mucosa (n = 44), colorectal adenomas (n = 63), carcinomas (n = 65), and various cancer cell lines (n = 46). Direct bisulphite sequencing was performed to confirm the MSP results. MAL gene expression was investigated with real time quantitative analyses before and after epigenetic drug treatment. Immunohistochemical analysis of MAL was done using normal colon mucosa samples (n = 5) and a tissue microarray with 292 colorectal tumors.

Results

Bisulphite sequencing revealed that the methylation was unequally distributed within the MAL promoter and by MSP analysis a region close to the transcription start point was shown to be hypermethylated in the majority of colorectal carcinomas (49/61, 80%) as well as in adenomas (45/63, 71%). In contrast, only a minority of the normal mucosa samples displayed hypermethylation (1/23, 4%). The hypermethylation of MAL was significantly associated with reduced or lost gene expression in in vitro models. Furthermore, removal of the methylation re-induced gene expression in colon cancer cell lines. Finally, MAL protein was expressed in epithelial cells of normal colon mucosa, but not in the malignant cells of the same type.

Conclusion

Promoter hypermethylation of MAL was present in the vast majority of benign and malignant colorectal tumors, and only rarely in normal mucosa, which makes it suitable as a diagnostic marker for early colorectal tumorigenesis.

Highly methylated genes in colorectal neoplasia: implications for screening

Discriminant markers are required for accurate cancer screening. We evaluated genes frequently methylated in colorectal neoplasia to identify the most discriminant ones. Four genes specifically methylated in colorectal cancer [bone morphogenetic protein 3 (BMP3), EYA2, aristaless-like homeobox-4 (ALX4), and vimentin] were selected from 41 candidate genes and evaluated on 74 cancers, 62 adenomas, and 70 normal epithelia. Methylation status was analyzed qualitatively and quantitatively and confirmed by bisulfite genomic sequencing. Effect of methylation on gene expression was evaluated in five colon cancer cell lines. K-ras and BRAF mutations were detected by sequencing. Methylation of BMP3, EYA2, ALX4, or vimentin was detected respectively in 66%, 66%, 68%, and 72% of cancers; 74%, 48%, 89%, and 84% of adenomas; and 7%, 5%, 11%, and 11% of normal epithelia (P < 0.01, cancer or adenoma versus normal). Based on area under the curve analyses, discrimination was not significantly improved by combining markers. Comethylation was frequent (two genes or more in 72% of cancers and 84% of adenomas), associated with proximal neoplasm site (P < 0.001), and linked with both BRAF and K-ras mutations (P < 0.01). Cell line experiments supported silencing of expression by methylation in all four study genes. This study shows BMP3, EYA2, ALX4, and vimentin genes are methylated in most colorectal neoplasms but rarely in normal epithelia. Comethylation of these genes is common, and pursuit of complementary markers for methylation-negative neoplasms is a rational strategy to optimize screening sensitivity.

Screening for colorectal cancer

Although there are several methods available for colon cancer screening, none is optimal. This article reviews methods for screening, including fecal occult blood tests, flexible sigmoidoscopy, colonoscopy, CT colonography, capsule endoscopy, and double contrast barium enema. A simple, inexpensive, noninvasive, and relatively sensitive screening test is needed to identify people at risk for developing advanced adenomas or colorectal cancer who would benefit from colonoscopy. It is hoped that new markers will be identified that perform better. Until then we fortunately have a variety of screening strategies that do work.

Pathophysiology, clinical presentation, and management of colon cancer

Colon cancer is believed to arise from two types of precursor polyps via two distinct pathways: conventional adenomas by the conventional adenoma-to-carcinoma sequence and serrated adenomas according to the serrated adenoma-to-carcinoma theory. Conventional adenomas arise from mutation of the APC gene; progression to colon cancer is a multistep process. The fundamental genetic defect in serrated adenomas is unknown. Environmental factors can increase the risk for colon cancer. Advanced colon cancer often presents with symptoms, but early colon cancer and premalignant adenomatous polyps commonly are asymptomatic, rendering them difficult to detect and providing the rationale for mass screening of adults over age 50.