Colorectal cancer screening by detection of altered human DNA in stool: feasibility of a multitarget assay panel

Flexible sigmoidoscopy for colorectal cancer screening: valid approach or short-sighted?

Flexible sigmoidoscopy is a safe, effective test that may be delivered feasibly on a large scale for mass colorectal cancer screening. Flexible sigmoidoscopy is 67% to 80% as sensitive as colonoscopy in a screening population, but is probably 10 to 20 times safer than colonoscopy in terms of complications. Several national guidelines recommend combining flexible sigmoidoscopy with fecal occult blood tests. There is limited evidence to support this practice, and the added benefit to an existing flexible sigmoidoscopy screening program although real, may be marginal. In the future, it is likely that flexible sigmoidoscopy screening among patients aged 50 to 65 will be supplemented with total colonic screening, using molecular-based fecal tests or virtual colonoscopy, after age 65.

Screening colonoscopy in balance. Issues of implementation

Although colonoscopy is currently considered an option for colon cancer screening, its choice as a preferred screening test is not supported by data, recommendations, or cost-effectiveness analysis. The use of colonoscopy in postpolypectomy surveillance constitutes a huge potential effort that should be appropriately anticipated and managed. Noninvasive methods for colon cancer screening may reduce the need for colonoscopy in the future.

The role of sigmoidoscopy and colonoscopy in the diagnosis and management of lower gastrointestinal disorders: endoscopic findings, therapy, and complications

Flexible sigmoidoscopy and colonoscopy have revolutionized the clinical management of colonic diseases. Colonoscopy is a highly sensitive and specific test. Colonic diseases often produce characteristic colonoscopic findings, as well as characteristic histologic findings, as identified in colonoscopic biopsy or polypectomy specimens. Colonoscopy is relatively safe, with a low incidence of serious complications, such as colonic perforation, hemorrhage, cardiopulmonary arrest, or sepsis. Colonoscopy is becoming more important clinically because of more widespread use of screening colonoscopy for colon cancer, application of therapeutic colonoscopy, and exciting new technical improvements.

Promoting early detection tests for colorectal carcinoma and adenomatous polyps: a framework for action: the strategic plan of the National Colorectal Cancer Roundtable

BACKGROUND

The purpose of the current study was to provide health professionals, professional organizations, policy makers, and the general public with a practical blueprint for increasing the practice of screening for colorectal carcinoma (CRC) and adenomatous polyps over the next decade. The National Colorectal Cancer Roundtable (NCCRT) was founded in 1997 by the American Cancer Society and the Centers for Disease Control and Prevention to provide strategic leadership, advocacy, long-range planning, and coordination of interventions targeted at reducing the disease burden of CRC through education, early detection, and prevention. The NCCRT and its three workgroups include CRC survivors; recognized experts in primary care, gastroenterology, radiology, colorectal surgery, nursing, public policy, epidemiology, and behavioral science; patient advocates; and representatives of health plans and insurers, government, and other organizations.

METHODS

The NCCRT performed a literature review of published and unpublished data related to CRC screening guidelines, compliance, and barriers to adherence, as well as test effectiveness and cost-effectiveness. Members of the three NCCRT workgroups developed summary reports regarding professional education, public education and awareness, and health policy. A drafting committee developed the final strategic plan from workgroup reports, which was reviewed by the entire NCCRT membership, amended, and subsequently approved in final form.

RESULTS AND CONCLUSIONS

Although the rationale for population-wide CRC screening is well established, the majority of adults in the U.S. are not currently being screened for CRC. Thus, the nation foregoes an opportunity to reduce CRC-related mortality by an estimated >or= 50%. To increase CRC screening rates, the issues of patient and physician barriers to screening, lack of universal coverage, lack of incentives to motivate adherence, and expanded infrastructure must be addressed.

Colorectal adenoma to carcinoma progression follows multiple pathways of chromosomal instability

BACKGROUND & AIMS

Current models of colorectal adenoma to carcinoma progression do not fully reflect the genetic heterogeneity and complexity of the disease. The aim of the present study was to identify genetic changes discriminating adenomas that have progressed to carcinoma from adenomas that have not progressed, and to refine the current genetic models of colorectal adenoma to carcinoma progression, based on a genome-wide analysis of chromosomal aberrations.

METHODS

Sixty-six nonprogressed colorectal adenomas, 46 progressed adenomas (malignant polyps), and 36 colorectal carcinomas were screened for chromosomal aberrations by comparative genomic hybridization, and for mutations in the adenomatous polyposis coli (APC) and K-ras gene. Data analysis focused on cancer-associated genetic changes in adenomas.

RESULTS

Accumulation of losses in 8p21-pter, 15q11-q21, 17p12-13, and 18q12-21, and gains in 8q23-qter, 13q14-31, and 20q13 were strongly associated with adenoma-to-carcinoma progression, independent of the degree of dysplasia. Hierarchic cluster analysis demonstrated the presence of 3 distinct subgroups of adenomas, characterized by unique combinations of genetic aberrations in the adenomas (17p loss and K-ras mutation, 8q and 13q gain, and 18q loss and 20q gain, respectively).

CONCLUSIONS

The presence of 2 or more of the aforementioned 7 chromosomal changes was associated with progressed colorectal adenomas and colorectal cancer. In addition, evidence was found that these chromosomal abnormalities occurred in specific combinations of a few abnormalities rather than as a mere accumulation of events, indicating the existence of multiple independent chromosomal instability pathways of colorectal cancer progression.

Colon cancer screening strategies

Screening has been shown to reduce morbidity and mortality related to colorectal cancer. However, the optimal strategy for population screening for colorectal cancer has been a topic of heated debate. Recent studies have challenged the efficacy and cost-effectiveness of current population screening practices. Novel approaches to improve the assessment of an individual's colorectal cancer risk and advances in technology are changing our approach to colorectal screening. This review covers current guidelines for screening for colorectal cancer, recent advances in cancer risk assessment, and the role of endoscopy, virtual colonoscopy, and fecal DNA testing in colorectal cancer screening.

Development of a fecal occult blood test using a monoclonal antibody to haptoglobin

Monoclonal antibodies (mAbs) were produced to human haptoglobin by immunising with fecal extracts from patients with colon cancer. An enzyme-linked immunosorbent assay was developed with one of the mAbs (FE14.1), and its ability to diagnose colorectal carcinoma evaluated. Patients with colorectal cancer were positive (43/46 = 93.5%) compared to normal individuals (4/211 = 1.9%). The assay has a specificity 93.5% and sensitivity 98.1% and has several advantages over current fecal occult blood tests. The test is potentially useful for bowel cancer diagnosis and to quantitate the level of haptoglobin in other body fluids such as urine and in effusions.

The genetic pathogenesis of colorectal cancer

Research over the past decade has established that the progression from normal colonic epithelium to colon cancer is in every case a step-wise process in which specific pathologic and molecular markers can be identified for study and clinical therapy. Genetic and epigenetic instability appears fundamentally important to this process. We have now determined that this neoplastic progression occurs along a limited set of pathways, in which specific tumor suppressors are inactivated or oncogenes activated in a defined order. Although incomplete, our new understanding of the process of carcinogenesis in the colon has already significantly impacted patient care and will continue to do so for the foreseeable future. Increasingly rapid research developments and technologic advances will transform the way we prevent, diagnose, and treat this common and deadly form of cancer.

Biomarkers in cancer screening: a public health perspective

The last three decades have witnessed a rapid advancement and diffusion of technology in health services. Technological innovations have given health service providers the means to diagnose and treat an increasing number of illnesses, including cancer. In this effort, research on biomarkers for cancer detection and risk assessment has taken a center stage in our effort to reduce cancer deaths. For the first time, scientists have the technologies to decipher and understand these biomarkers and to apply them to earlier cancer detection. By identifying people at high risk of developing cancer, it would be possible to develop intervention efforts on prevention rather than treatment. Once fully developed and validated, then the regular clinical use of biomarkers in early detection and risk assessment will meet nationally recognized health care needs: detection of cancer at its earliest stage. The dramatic rise in health care costs in the past three decades is partly related to the proliferation of new technologies. More recent analysis indicates that technological change, such as new procedures, products and capabilities, is the primary explanation of the historical increase in expenditure. Biomarkers are the new entrants in this competing environment. Biomarkers are considered as a competing, halfway or add-on technology. Technology such as laboratory tests of biomarkers will cost less compared with computed tomography (CT) scans and other radiographs. However, biomarkers for earlier detection and risk assessment have not achieved the level of confidence required for clinical applications. This paper discusses some issues related to biomarker development, validation and quality assurance. Some data on the trends of diagnostic technologies, proteomics and genomics are presented and discussed in terms of the market share. Eventually, the use of biomarkers in health care could reduce cost by providing noninvasive, sensitive and reliable assays at a fraction of the cost of definitive technology, such as CT scan. The National Cancer Institute's Early Detection Research Network (EDRN) has begun an innovative, investigator-initiated project to improve methods for detecting the biomarkers of cancer cells. The EDRN is a consortium of more than 32 institutions to link discovery of biomarkers to the next steps in the process of developing early detection tests. These discoveries will lead to early clinical validation of tests with improved accuracy and reliability.

Secondary prevention: screening and surveillance of persons at average and high risk for colorectal cancer

Secondary prevention of colorectal cancer with FOBT and endoscopy with polypectomy decreases cancer deaths. Other available modalities include genetic tests and imaging studies, but outcomes data are not yet available. Issues remain concerning the most appropriate test, the optimal intervals, and cost-efficacy. Patients may be stratified by personal and family risk, and specific strategies may be used. Newer developments in genetic tests and imaging, including virtual colonoscopy, hold promise for the future. The most important issue at present is to have people screened or surveilled by any of the recommended modalities.

The promise of biomarkers in cancer screening and detection

Despite the recent decline in the incidence of cancer, long-term mortality rates remain unchanged. One of the most important factors in the survival of cancer is detection at an early stage. Clinical assays that detect the early events of cancer offer an opportunity to intervene and prevent cancer progression. Biomarkers are important molecular signatures of the phenotype of a cell that aid in early cancer detection and risk assessment. Although new information and technologies are clearly important for new biomarker discovery, we face major hurdles in translating new findings into clinical application. Here, we discuss examples of recent advances and limitations in cancer biomarker identification and validation, and the implications for cancer prevention.

Colon cancer: detection and prevention

Recent data have advanced our ability to detect, survey, and manage patients with colonic neoplasia. Current studies and consensus statements increasingly support the role of colonoscopic screening over less invasive testing such as FOBT or FS for appropriately selected individuals. There are many issues, however, that remain unresolved. What is the appropriate surveillance of an individual with a single family member who had colon cancer at an early age? How should family members of suspected HNPCC kindreds be managed? There has yet to be a prospective cohort validation of the Bethesda criteria in directing clinical practice, with the endpoint of mortality reduction. Questions regarding prophylaxis with dietary supplements and medications are exciting areas that are currently under study. As newer technologies become clinically available for molecular diagnostics and screening, and virtual colonoscopy with computed tomography and magnetic resonance disseminates, there will undoubtedly be new questions to be answered regarding their ability to aid in the detection and management of colon cancer.

Cellular and molecular mechanisms of carcinogenesis

Our understanding of the cellular and molecular mechanisms of cancer of the gastrointestinal tract has increased dramatically over the last several decades. We are identifying new players in the pathways toward cancer with increasing frequency. In addition, we have come to understand that no single pathway acts by itself; in vivo, the effects are combinatorial. As new and better cell culture and animal models of carcinogenesis arise, our knowledge will continue to grow. As we learn more, we will be able to translate the results of our research into new and better techniques for the diagnosis and treatment of gastrointestinal cancers.

Colorectal cancer screening: an overview of current trends

Colorectal cancer can be cured and, in some cases, even prevented if detected early through screening. Studies have demonstrated that regular screening for colorectal cancer with fecal occult blood testing, sigmoidoscopy, or colonoscopy can reduce mortality from this disease. Unfortunately, rates of participation in these screening tests are unacceptably low among the U.S. population. Nurses have a significant role to play in assisting individuals to incorporate regular colorectal cancer screening into their health maintenance routines.

Prognosis and response to therapy in colorectal cancer

Colorectal cancer is Europe's second biggest cancer killer. Yet despite advances in knowledge and changes in chemotherapy practice, we have not seen great strides in improved survival. Histopathological staging is at present the most accurate prognostic factor for survival and recurrence. Improvements in staging have led to the recognition of the importance of the circumferential resection margin (CRM) and how the quality of surgery influences local recurrence rates. Further refinements in staging and increasing knowledge of tumour biology will have a large contribution to play in the future.

Microsatellite analysis of fecal DNA for colorectal cancer detection

BACKGROUND AND OBJECTIVES

The advent of noninvasive methods of testing for colorectal cancer that have a high level of specificity and sensitivity is eagerly awaited.

METHODS

Thirty patients with sporadic colorectal cancer and 11 patients with hereditary nonpolyposis colon cancer (HNPCC) enrolled in this study. We analyzed the loss of heterozygosity (LOH) in matched genomic DNA extracted from blood and surgical specimens (tumor and tumor-free colonic mucosa), and the corresponding oral rinse and stool specimens using seven microsatellite loci (APC, p53, DCC, hMLH1, D9S162, D9S171, and IFNA). To reduce the normal colonocyte DNA contamination of the stool samples, we compared three different methods for fecal genomic DNA extraction. As normal controls, we analyzed the LOH using the oral rinse and stool samples from 15 individuals without cancer.

RESULTS

The LOH determined from the oral rinse and the stool samples matched those determined from the blood and the neoplastic tissue. All patients with HNPCC had microsatellite alterations at hMLH-1 in tumor DNA and corresponding fecal DNA. There were significant differences in the frequency of p53-LOH and D9S171-LOH between the group with sporadic disease and those with HNSCC (P = 0.0031 and 0.0294, respectively). Two cases with D9S162-LOH were detected in individuals without cancer. For the patients with sporadic disease, using p53 and adenomatous polyposis coli (APC), the sensitivity of the fecal DNA analysis was 96.7% (95% CI, 83-100) with a specificity of 100%.

CONCLUSION

We demonstrate that LOH analysis using oral rinse and stool samples may be a suitable screening tool for colorectal cancer.

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.

Emerging molecular markers of cancer

Alterations in gene sequences, expression levels and protein structure or function have been associated with every type of cancer. These 'molecular markers' can be useful in detecting cancer, determining prognosis and monitoring disease progression or therapeutic response. But what is the best way to identify molecular markers and can they be easily incorporated into the clinical setting?

Isolation of exfoliated colonocytes from human stool as a new technique for colonic cytology

Cell exfoliation in the gut is an important cell renewal mechanism. To approach its investigation we applied a novel immunomagnetic technique for isolation of exfoliated cells from human stool. Exfoliated colonocytes were isolated from 168 stool samples. The cells were assessed microscopically using conventional stains and immunohistochemistry. The technique allowed us to obtain well-preserved colonocytes displaying characteristic features of well-differentiated colonic epithelium and positive immunostaining for cytokeratin 5/8. No mucin-producing cells were found. Exfoliated cells did not produce inducible nitric oxide synthase, albeit cultured colon carcinoma cells HT-29 analysed in parallel showed strong immunostaining. Analysis of exfoliated cell numbers in consecutive stool samples from the same subjects revealed considerable interindividual variation. Overall exfoliated colonocyte numbers were relatively low, isolation being unaffected by addition during the procedure of excessive amounts of HT-29 cells. Apoptosis was extremely rare among exfoliated colonocytes. Well-preserved exfoliated colonocytes can be consistently isolated from human faeces using a simple procedure. Our findings suggest that the actual process of cell exfoliation in the human colon may be much less intense than is generally accepted. Exfoliated cell isolation from human stool constitutes a convenient non-invasive approach that can be used for diagnostic and research purposes.

Detection of tumor mutations in the presence of excess amounts of normal DNA

Mutations are important markers in the early detection of cancer. Clinical specimens such as bodily fluid samples often contain a small percentage of mutated cells in a large background of normal cells. Thus, assays to detect mutations leading to cancer need to be highly sensitive and specific. In addition, they should be possible to carry out in an automated and high-throughput manner to allow large-scale screening. Here we describe a screening method, termed PPEM (PNA-directed PCR, primer extension, MALDI-TOF), that addresses these needs more effectively than do existing methods. DNA samples are first amplified using peptide nucleic acid (PNA)-directed PCR clamping reactions in which mutated DNA is preferentially enriched. The PCR-amplified DNA fragments are then sequenced through primer extension to generate diagnostic products. Finally, mutations are identified using matrix-assisted laser-desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. This method can detect as few as 3 copies of mutant alleles in the presence of a 10,000-fold excess of normal alleles in a robust and specific manner. In addition, the method can be adapted for simultaneous detection of multiple mutations and is amenable to high-throughput automation.

Colorectal cancer risk: the impact of evidence of a field effect of carcinogenesis on blinded diagnosis using an anti-adenoma antibody test performed on colonoscopic effluent

To better define high-risk populations for colorectal cancer screening, we used anti-adenoma antibody Adnab-9, comparing colonic effluent and tissue field effects from 45 high-risk and 11 control patients. We included Adnab-9 binding at the tissue level to elucidate the impact of a field effect of carcinogenesis contributing to the outcome of the effluent binding test. In high-risk patients, 64% of the left-sided effluent samples were positive (P < 0.002); 67% showed a field effect (P < 0.006); 82% of combined tests were positive (P < 0.001), as compared to 9%, 18%, and 27% respectively, of controls. Adnab-9 binding correlates with increased colorectal cancer risk associated with a field effect of carcinogenesis.

Detection of APC mutations in fecal DNA from patients with colorectal tumors

BACKGROUND

Noninvasive methods for detecting colorectal tumors have the potential to reduce morbidity and mortality from this disease. The mutations in the adenomatous polyposis coli (APC) gene that initiate colorectal tumors theoretically provide an optimal marker for detecting colorectal tumors. The purpose of our study was to determine the feasibility of detecting APC mutations in fecal DNA with the use of newly developed methods.

METHODS

We purified DNA from routinely collected stool samples and screened for APC mutations with the use of a novel approach called digital protein truncation. Many different mutations could potentially be identified in a sensitive and specific manner with this technique.

RESULTS

Stool samples from 28 patients with nonmetastatic colorectal cancers, 18 patients with adenomas that were at least 1 cm in diameter, and 28 control patients without neoplastic disease were studied. APC mutations were identified in 26 of the 46 patients with neoplasia (57 percent; 95 percent confidence interval, 41 to 71 percent) and in none of the 28 control patients (0 percent; 95 percent confidence interval, 0 to 12 percent; P<0.001). In the patients with positive tests, mutant APC genes made up 0.4 to 14.1 percent of all APC genes in the stool.

CONCLUSIONS

APC mutations can be detected in fecal DNA from patients with relatively early colorectal tumors. This feasibility study suggests a new approach for the early detection of colorectal neoplasms.

Stool screening for colorectal cancer: evolution from occult blood to molecular markers

BACKGROUND

Colorectal cancer is the second leading cause of malignant death, and better preventive strategies are needed. Participation rates for colorectal cancer screening remain low due, in part, to perceived discomfort, potential harm, and high costs with available tools.

METHODS

Stool testing, unlike other conventional screening approaches, is noninvasive and requires no cathartic preparation. However, widely used fecal blood tests yield frequent false-negative and false-positive results that lower screening effectiveness and raise program costs. There is a compelling biological rationale to target DNA alterations exfoliated from neoplasms into stool, and multiple DNA markers would need to be assayed because of the genetic heterogeneity of colorectal neoplasia. Early clinical studies with this multi-target DNA-based stool assay approach suggest high sensitivity for both colorectal cancer and premalignant adenomatous polyps while maintaining high specificity.

CONCLUSIONS

This apparently accurate and user-friendly new approach holds promise to improve the effectiveness, efficiency, and appeal of colorectal cancer screening. Large-scale clinical studies are clearly warranted to corroborate the early results.

The advanced adenoma as the primary target of screening

The advanced adenoma bridges benign and malignant states and may be the most valid neoplastic surrogate marker for present and future colorectal cancer risk. We define the advanced adenoma as an adenoma with significant villous features (>25%), size of 1.0 cm or more, high-grade dysplasia, or early invasive cancer. Prevention studies should demonstrate a high efficacy in reducing the number of advanced adenomas. We should use the advanced adenoma in the evaluation of new screening technology, nutritional interventions, and chemoprevention agents because the advanced adenoma is a more desirable target for screening efficacy than is the more uncommon but life-threatening cancer stage or the more common but early, less significant small adenoma stage.

Fecal occult blood testing for colorectal cancer: a perspective

Colorectal cancer is an important health problem in western countries. Early detection of colorectal cancer reduces mortality. The best evidence for the effectiveness of screening for colorectal cancer is with annual or biennial fecal occult blood testing. While the benefit of fecal occult blood testing is small in absolute terms, the incremental cost-effectiveness of this screening strategy appears acceptable. Combining fecal occult blood testing with periodic flexible sigmoidoscopy or replacing it altogether with infrequent colonoscopy are theoretically attractive screening strategies, but the incremental costs and effectiveness of these more intensive screening strategies have not been well defined. Whether and how to implement population-based screening for colorectal cancer depends largely on available resources.

Accurate, noninvasive detection of Helicobacter pylori DNA from stool samples: potential usefulness for monitoring treatment

A novel DNA assay demonstrating sensitive and accurate detection of Helicobacter pylori from stool samples is reported. Moreover, in three individuals tested for therapeutic response, the assay showed the disappearance of H. pylori DNA during treatment. Thus, this noninvasive molecular biology-based assay has the potential to be a powerful diagnostic tool given its ability to specifically identify H. pylori DNA.

Barriers to screening for colorectal cancer

Rapidly growing interest in colon cancer screening is a crucial first step to identifying and reducing many of the barriers that impede population screening for this common disease. Promoting screening demands health care policy change to increase the percentage of Americans with insurance coverage that includes a colon cancer screening benefit. A systematic approach to screening with invitations that come from a clinician are likely to be the most effective way to prompt more individuals to be screened. Awareness campaigns and patient educational aids, including decision tools, implemented in multiple sites, such as worksites, community centers, health care systems, and physician offices, increase the percent of eligible Americans who understand their personal risk, the need for screening, and the options available to them.

Flexible sigmoidoscopy: an important screening option for average-risk individuals

Colorectal cancer screening techniques should be effective, acceptable to patients, affordable, widely available, and safe. For average-risk adults aged more than 50 years who do not have significant colorectal symptoms, significant family history, or significant predisposing conditions, flexible sigmoidoscopy is an important option for reducing the risk for colorectal cancer, meeting all criteria for an effective and feasible screening modality. This article discusses evidence supporting flexible sigmoidoscopy, practical issues in implementation, and current controversies.

The case for population-based screening for colorectal cancer

Screening for colorectal cancer is commanding increasing attention. Other cancer screening programmes have been a part of public consciousness for some time, but, until recently, colorectal cancer screening has remained in the background. Fuelled by new research, market opportunities and increased recognition of individual risk, screening for colorectal cancer is becoming a recommended procedure, but controversy about how best to implement widespread screening remains.

Phenotypic variation in eight extended CDKN2A germline mutation familial atypical multiple mole melanoma-pancreatic carcinoma-prone families: the familial atypical mole melanoma-pancreatic carcinoma syndrome

BACKGROUND

Hereditary pancreatic carcinoma shows extant phenotypic and genotypic heterogeneity as evidenced by its integral association with a variety of hereditary cancer syndromes inclusive of the familial atypical multiple mole melanoma (FAMMM) syndrome in concert with CDKN2A (p16) germline mutations.

METHODS

Creighton University's familial pancreatic carcinoma resource comprises 159 families of which 19 (12%) show the FAMMM cutaneous phenotypes. The authors describe eight families with the FAMMM-pancreatic carcinoma (FAMMM-PC) association in concert with a CDKN2A germline mutation. Each family was thoroughly educated about all facets of the study, including the molecular genetics, reduced penetrance of CDKN2A mutations, and their variable expressivity. Genetic counseling was provided to each patient.

RESULTS

Diversity in cancer presentation within and among the families was noteworthy, wherein melanoma predominated in certain of the families whereas pancreatic carcinoma predominated in others. Early-onset pancreatic carcinoma (at ages 35, 45, 46, and 49 years) appeared in some of the families whereas markedly later-onset pancreatic carcinoma occurred in others. There were four incidences of melanoma and pancreatic carcinoma as double primaries in the same individuals. One patient with melanoma and pancreatic carcinoma had a third primary of breast carcinoma. Another patient had sarcoma, esophageal carcinoma, and two melanoma primaries, whereas his daughter had sarcoma and was a carrier of a CDKN2A mutation.

CONCLUSIONS

The authors suggest that these tumors may collectively, in concert with CDKN2A mutations, constitute a "new" putative hereditary carcinoma syndrome referred to as FAMMM-PC. More clinical and molecular genetic research on additional families with pancreatic carcinoma in concert with the FAMMM will be required.

The future of colon cancer prevention

Chemoprevention science is in flux owing to rapid advances in postgenomic technology. We have witnessed enormous advances in the areas of early detection and molecular profiling of colorectal carcinogenesis; however, unique interpretive and technologic challenges persist. Neoplastic hallmarks must be iteratively tested and validated as markers of risk, targets for intervention, and/or markers of response in order to expedite the development of preventive interventions. In this review, we highlight several of the technologies that are revolutionizing our understanding of carcinogenesis and our approach to colorectal cancer prevention.

Gene mutation as a target for early detection in cancer diagnosis

The increasing number of genetic aberrations implicated in the development of human cancer has prompted a search to detect them at the earliest possible stage of their formation. Of the many such genetic changes identified thus far, relatively few meet the standard for markers in early diagnosis and prognosis, namely that the genetic modifications occur during the early onset phase of cancer development. Parallel to the increasing number of such genes is the growing availability of technologies using more powerful and cost-efficient methods that enable mass screening for genetic alterations. The purpose of this review is to summarize the currently available genes that can serve as markers for early detection of cancers and methods that allow their detection.

Trends in biomarker research for cancer detection

A key challenge in cancer control and prevention is detection of the disease as early as possible, enabling effective interventions and therapies to contribute to reduction in mortality and morbidity. Biomarkers are important as molecular signposts of the physiological state of a cell at a specific time. Active genes, their respective protein products, and other organic chemicals made by the cell create these signposts. As a normal cell progresses through the complex process of transformation to a cancerous state, biomarkers could prove vital for the identification of early cancer and people at risk of developing cancer. We discuss current research into the genetic and molecular signatures of cells, including microsatellite instability, hypermethylation and single-nucleotide polymorphisms. The use of genomic and proteomic high-throughput technology platforms to facilitate detection of early cancer by means of biomarkers, and issues on the analysis, validation, and predictive value of biomarkers based on these technologies are also discussed. We report on recent advances in identifying sources of biomarkers that can be accessed by noninvasive techniques, such as buccal-cell isolates, as well as traditional sources such as serum or plasma. We also focus on the work of the Early Detection Research Network at the National Cancer Institute, harnessing expertise from leading national and international institutions, to identify and validate biomarkers for the detection of precancerous and cancerous cells in assessing risk of cancer. The network also has a role in linking discovery to process development, resulting in early detection tests and clinical assessment.

Detecting colorectal cancer in stool with the use of multiple genetic targets

BACKGROUND

Colorectal cancer cells are shed into the stool, providing a potential means for the early detection of the disease using noninvasive approaches. Our goal was to develop reliable, specific molecular genetic tests for the detection of colorectal cancer in stool samples.

METHODS

Stool DNA was isolated from paired stools and primary tumor samples from 51 colorectal cancer patients. Three genetic targets-TP53, BAT26, and K-RAS-were used to detect tumor-associated mutations in the stool prior to or without regard to the molecular analyses of the paired tumors. TP53 gene mutations were detected with a mismatch-ligation assay that detects nine common p53 gene mutations. Deletions within the BAT26 locus were detected by a modified solid-phase minisequencing method. Mutations in codons 12 and 13 of K-RAS were detected with a digital polymerase chain reaction-based method.

RESULTS

TP53 gene mutations were detected in the tumor DNA of 30 patients, all of whom had the identical TP53 mutation in their stools. Tumors from three patients contained a noninherited deletion at the BAT26 locus, and the same alterations were identified in these patients' stool specimens. Nineteen of 50 tumors tested had a K-RAS mutation; identical mutations were detected in the paired stool DNA samples from eight patients. In no case was a mutation found in stool that was not also present in the primary tumor. Thus, the three genetic markers together detected 36 (71%) of 51 patients (95% confidence interval [CI] = 56% to 83%) with colorectal cancer and 36 (92%) of 39 patients (95% CI = 79% to 98%) whose tumors had an alteration.

CONCLUSION

We were able to detect the majority of colorectal cancers by analyzing stool DNA for just three genetic markers. Additional work is needed to determine the specificity of these genetic tests for detecting colorectal neoplasia in asymptomatic patients and to more precisely estimate the prevalence of the mutations and sensitivity of the assay.

Lack of prognostic influence of circulating tumor cells in peripheral blood of patients with colorectal cancer

BACKGROUND AND AIMS

Circulating tumor cells in peripheral blood may be detected using high-sensitivity molecular techniques in several types of solid neoplasms, but their significance in colorectal cancer is controversial. The aim of this study was to assess the prognostic value of carcinoembryonic antigen (CEA) messenger RNA (mRNA) detection in peripheral blood samples from patients with colorectal cancer.

METHODS

Peripheral vein blood samples from 95 consecutive patients with histologically confirmed colorectal carcinoma were obtained immediately before surgery to determine the presence of circulating tumor cells by use of a reverse-transcription polymerase chain reaction targeting CEA mRNA. Endpoints of the study were disease-free and overall survival. Results are referred to the whole series and, more importantly, to the 68 patients who underwent surgery for cure.

RESULTS

After a median follow-up of 42 months, 19 of 68 patients (28%) operated on for cure had tumor relapse. In addition, 50 of 68 patients (73%) were alive. The probability of disease-free and overall survival was dependent on lymph node metastases and degree of differentiation, but not on the presence of circulating tumor cells (disease-free survival: relative risk, 1.00; 95% confidence interval [CI], 0.39-2.22, P = 0.99; overall survival: relative risk, 0.91, 95% CI, 0.34-2.43; P = 0.84). Similar results were obtained when all 95 patients with colorectal cancer were analyzed (disease-free survival: relative risk, 1.11; 95% CI, 0.63-1.95; P = 0.71; overall survival: relative risk, 1.21; 95% CI, 0.63-2.30, P = 0.55).

CONCLUSIONS

Preoperative detection of blood circulating tumor cells by means of reverse-transcription polymerase chain reaction of CEA does not have prognostic significance in patients with colorectal cancer.