A smarter strategy? Reflections on fecal DNA screening for colorectal cancer

Serum methylation levels of TAC1. SEPT9 and EYA4 as diagnostic markers for early colorectal cancers: a pilot study

OBJECTIVE

To identify methylated genes in serum with diagnostic potentials for early colorectal cancer (CRC).

METHODS

Serum methylation levels of up to 12 genes were measured in two sets of serum samples with the second set from 26 stage I CRC patients and 26 age/gender-matched controls.

RESULTS

Serum methylation levels of TAC1, SEPT9, and EYA4 were significant discriminants between stage I CRC and healthy controls. Combination of TAC1 and SEPT9 rendered 73.1% sensitivity with 92.3% specificity.

CONCLUSION

Serum methylation levels of TAC1. SEPT9 and EYA4 may be useful biomarkers for early detection of CRC though a validation study is necessary.

Multiplexed VeraCode bead-based serological immunoassay for colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer deaths in the US and Western world. Despite increased screening and advances in treatment, the mortality rate (ca. 50,000/year) and high national health-care burden for CRC are likely to remain high unless an effective non-invasive screening test for CRC is instituted for a large segment of the population. Blood-based protein biomarkers hold great promise for early disease diagnosis and personalized medicine; yet robust and reproducible multiplexing platforms and methodologies have lagged behind their genomic counterparts. Here, we report the development of a novel, multiplexed, hybrid immunoassay for CRC that is formatted on barcoded VeraCode™ micro-beads, which have until now only been used for genomic assays. The method combines a sandwich immunoassay format for detection of serum protein biomarkers with an antigen assay for autoantibody detection. The serum protein biomarkers CEA and GDF15 as well as autoantibodies to the p53 tumor associated antigen (TAA) were used to exemplify the method. This multiplex biomarker panel was configured to run on Illumina's holographically barcoded VeraCode™ micro-bead platform, which is capable of measuring hundreds of analytes simultaneously in a single well from small volumes of blood (<50 μL) using a 96-well industry standard microtiter plate. This novel use of the VeraCode™ micro-bead platform translates into a potentially low volume, high throughput, multiplexed assay for CRC, for the purposes of biomarker validation, as well as patient screening, diagnostics and prognostics. In an evaluation of a 186 patient sera training set (CRC and normal), we obtained a diagnostic sensitivity of 54% and a specificity of 98%. We anticipate that by expanding and refining the biomarkers in this initial panel, and performing more extensive clinical validations, such an assay could ultimately provide a basis for CRC population screening to complement the more invasive, expensive and low throughput (but highly sensitive and specific) colonoscopy.

Colorectal cancer screening: Comparison of transferrin and immuno fecal occult blood test

AIM: To evaluate the sensitivity and specificity of transfesrrin dipstick test (Tf) in colorectal cancer (CRC) screening and precancerous lesions screening.

METHODS: Eight hundreds and sixty-one individuals at high-risk for CRC were recruited. Six hundreds and eleven subsequently received the three fecal occult blood tests and colonoscopy with biopsy performed as needed. Fecal samples were obtained on the day before colonoscopy. Tf, immuno fecal occult blood test (IFOBT) and guaiac fecal occult blood test (g-FOBT) were performed simultaneously on the same stool. To minimize false-negative cases, all subjects with negative samples were asked to provide an additional stool specimen for a second test even a third test. If the results were all negative after testing three repeated samples, the subject was considered a true negative. The performance characteristics of Tf for detecting CRC and precancerous lesions were examined and compared to those of IFOBT and the combination of Tf, IFOBT and g-FOBT.

RESULTS: A total of six hundreds and eleven subjects met the study criteria including 25 with CRC and 60 with precancerous lesions. Sensitivity for detecting CRC was 92% for Tf and 96% for IFOBT, specificities of Tf and IFOBT were both 72.0% (95% CI: 68.2%-75.5%; χ² = 0.4, P > 0.05); positive likelihood ratios of those were 3.3 (95% CI: 2.8-3.9) and 3.4 (95% CI: 2.9-4.0), respectively. In precancerous lesions, sensitivities for Tf and IFOBT were 50% and 58%, respectively (χ² = 0.8, P > 0.05); specificities of Tf and IFOBT were 71.5% (95% CI: 67.6%-75.1%) and 72.2% (95% CI: 68.4%-75.8%); positive likelihood ratios of those were 1.8 (95% CI: 1.3-2.3) and 2.1 (95% CI: 1.6-2.7), respectively; compared to IFOBT, g-FOBT+ Tf+ IFOBT had a significantly higher positive rate for precancerous lesions (83% vs 58%, respectively; χ² = 9.1, P < 0.05). In patients with CRC and precancerous lesions, the sensitivities of Tf and IFOBT were 62% and 69% (χ² = 0.9, P > 0.05); specificities of those were 74.5% (95% CI: 70.6%-78.1%) and 75.5% (95% CI: 71.6%-79.0%); positive likelihood ratios of those were 2.5 (95% CI: 2.0-3.1) and 2.8 (95% CI: 2.3-3.5). Compared to IFOBT alone, combining g-FOBT, IFOBT and Tf led to significantly increased sensitivity for detecting CRC and cancerous lesions (69% vs 88%, respectively; χ² = 9.0, P < 0.05).

CONCLUSION: Tf dipstick test might be used as an additional tool for CRC and precancerous lesions screening in a high-risk cohort.

Perspectives on the treatment of colorectal carcinoma

Colorectal cancer includes cancerous growths in the colon, rectum and appendix. With 655000 deaths worldwide per year, it is the third most common form of cancer and the second leading cause of cancer-related death in the Western world. Advances in imaging, genetics, molecular diagnostics, surgical techniques and chemotherapy are now making significant gains in our ability to prevent, diagnose, and treat this serious disease. This article reviews some of these recent successes and shares a vision of future care based on current research.

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.

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.

Colorectal cancer screening tests: pros and cons, and for whom?

The past decade has seen major advances internationally in the implementation of colorectal cancer screening, influenced in differing ways by the profession, the public and by government. Relatively unique to colorectal cancer screening is the availability of so many test alternatives, which have substantial variation in methodology. While perhaps spoilt for choice, discerning the key advantages and disadvantages of each test is often difficult, depending on the perspective from which screening is viewed. Accordingly, this article provides an evaluation of screening tests as might be perceived by governments, the patient and the profession. Aligned issues such as choosing a screening test and provision of informed consent are discussed. Finally, the article identifies current problems with various screening tests that, if attended to, might change the perception of a test's value to a particular interest group.

Cell exfoliation in the human colon: myth, reality and implications for colorectal cancer screening

Colonocyte exfoliation in the human colon constitutes a unique mechanism of cell population control that can undergo significant changes under different physiological and pathological conditions. Being closely related to the apoptosis and anoikis, cell exfoliation from colonic epithelium appears to be a relatively rare event in normal conditions, but its rate dramatically increases in neoplasia, when cell removal by apoptosis in situ does not function properly. Several studies show that significant numbers of exfoliated colonocytes are not lost in the faecal contents of the gut, but retained in the mucocellular layer overlying colonic mucosa. Recent observations allow hypothesizing that the mucocellular layer containing exfoliated colonocytes may gradually migrate distally, eventually leading to the accumulation of the cells exfoliated from malignant colorectal tumours on the surface of the rectal mucosa. Implications of exfoliated colonocyte analysis to colorectal cancer screening and early diagnosis are discussed.

Value of fecal tumor M2 pyruvate kinase in diagnosis of colorectal cancer

AIM: To evaluate the value of fecal M₂ pyruvate kinase (M₂-PK) as a screening biomarker for colorectal cancer.

METHODS: The tumor fecal M₂-PK was determined by enzyme-linked immunosorbent assay (ELISA) in colorectal cancer patients (n = 80) and healthy controls (n = 80), and the results were comparatively analyzed.

RESULTS: The cut-off value to discriminate patients from controls was established at 166.7 mkat/L for tumor M₂-PK. The mean level of fecal tumor M₂-PK was significantly higher in colorectal cancer patients than that in the normal controls (713.41 mkat/L vs 59.55 mkat/L, P < 0.0001), and the overall sensitivity and specificity were 77.5% and 92.5%, respectively. With the progression of colorectal carcinoma, the level of tumor M2-PK as well as the sensitivity was increased (F = 52.984, P < 0.0001). In patients with Dukes A (n = 11), B (n = 37), C (n = 25), and D (n = 7) stages, the mean levels of tumor M₂-PK were 233.53, 522.58, 847.27 and 1998.04 mkat/L, respectively, and the sensitivities were 63.64%, 75.68%, 84% and 84%, respectively.

CONCLUSION: Tumor M₂-PK is detectable in the feces of colorectal cancer patients and correlated with the staging and metastasis of the carcinoma, and it can help to make early diagnosis of colorectal cancer in patients with sub-clinical symptoms.

Colorectal cancer screening: physicians' knowledge of risk assessment and guidelines, practice, and description of barriers and facilitators

BACKGROUND

Physician nonadherence to colorectal cancer (CRC) screening recommendations contributes to underuse of screening.

OBJECTIVE

To assess physicians' knowledge of CRC screening guidelines for average-risk individuals, perceived barriers to screening and practice behaviours.

METHODS

Between October 2004 and March 2005, staff physicians working in three university-affiliated hospitals in Montreal, Quebec, were surveyed. Self-administered questionnaires assessed knowledge of risk classification and current guidelines for average-risk individuals, as well as perceptions of barriers to screening and practice behaviours.

RESULTS

All 65 invited physicians participated in the survey, including 46 (70.8%) family medicine physicians and 19 (29.2%) general internists. Most physicians knew that screening should begin at 50 years of age, all knew to screen men and women and 92% said they screened average-risk patients. Fifty-seven (87.7%) physicians correctly identified three common characteristics associated with high risk for developing CRC. Physicians who screened average-risk patients preferred fecal occult blood testing (88.3%) and colonoscopy (88.3%) to flexible sigmoidoscopy (10.0%) and double-contrast barium enema (30.0%). Most physicians knew the correct screening periodicity for fecal occult blood testing (87.6%), but only 40% or fewer could identify correct screening periodicities for the other modalities. Barriers and facilitators focused on health care delivery system improvements, better evidence on which to base recommendations and development of practical screening modalities.

CONCLUSIONS

Physicians lacked knowledge of the recommended screening modalities and periodicities to appropriately screen average-risk individuals. Because CRC screening can reduce mortality, efforts to improve physician delivery should focus on physician knowledge and changes to the health care delivery system.

Clinical Implications of Our Advancing Knowledge of Colorectal Cancer Genetics: Inherited Syndromes, Prognosis, Prevention, Screening and Therapeutics

Recent genetic advances in our knowledge of colorectal cancer genetics are beginning to pay translational dividends in the management of this common clinical problem. We are now able to accurately screen and counsel individuals at risk of rare inherited cancer syndromes. We have recently introduced two of what are sure to be numerous biologic-based therapies, and have shown that colorectal neoplasia risk can be modestly reduced by various chemopreventative agents. Finally, our advancing knowledge has led to significant inroads into understanding what genetic alterations define prognosis and predict response to specific chemotherapeutic agents, and we are beginning to explore the utility of this knowledge in mass genetic-based clinical screening efforts. Enthusiasm must be tempered, however, by the extraordinary cost that often accompanies relatively modest gains. Finally, although genetic-based therapy often receives the greatest attention, molecular genetics, will likely have the greatest cost-effective impact in primary prevention and early diagnosis.

Comparative evaluation of a new bedside faecal occult blood test in a prospective multicentre study

BACKGROUND

Faecal occult blood testing is an established method of colorectal neoplasia screening. Guaiac-based tests are limited by poor patient compliance, low sensitivity, specificity and positive predictive value. Newer immunochemical-based tests, accurate but tedious, require a well-established laboratory set up. There is need for simpler immunochemical tests that can be performed at the out-patient clinic.

AIM

To compare the performance characteristics of a new bedside immunological test strip device with a sensitive Guaiac-based and established immunochemical test for detection of faecal occult blood in patients undergoing colonoscopy.

METHODS

A total of 389 consecutive patients from four centres who were referred for colonoscopy also provided the stool samples for detection of occult blood without dietary restrictions. Stool tests performed were (i) Guaiac-based, (ii) immunochemical enzyme-linked immunosorbent assay and (iii) bedside immunochemical strip test.

RESULTS

At the optimal threshold level, the sensitivity and specificity of the beside immunochemical strip test for detection of significant colorectal neoplasia (adenomas >1.0 cm and carcinomas) were 60% and 95%, respectively.

CONCLUSIONS

This bedside immunochemical strip test proved to be a simple, convenient, non-cumbersome and accurate tool with similar performance characteristics for detection of any bleeding lesion including colorectal neoplasia when compared with an established immunochemical faecal occult blood test.

Prospective multicenter evaluation of fecal tumor pyruvate kinase type M2 (M2-PK) as a screening biomarker for colorectal neoplasia

Proliferating cells, particularly the tumor cells, express a dimeric isoenzyme of pyruvate kinase, termed M2-PK. It's a direct target of several oncoproteins; the determination of fecal tumor pyruvate kinase type M2 (M2-PK) might be another promising tool for colorectal cancer (CRC) screening. In this study, we have evaluated fecal M2-PK as a screening biomarker for colorectal neoplasia. It was compared against fecal occult blood (FOB) and colonoscopy. Three hundred and seventeen consecutive subjects from 4 different centers were included. Stool specimens were collected before purgation, processed appropriately and were tested for FOB and quantitatively analyzed for M2-PK. Colonoscopies were performed by experienced endoscopists who were unaware of fecal assay results. At cutoff value of 4 U/ml, fecal M2-PK assay had a sensitivity, specificity, PPV and NPV of 81.1, 86.7, 71.1 and 61.9% respectively for diagnosing CRC whereas FOBT showed a sensitivity of 36.5%, specificity of 92.2%, PPV of 72.9% and NPV of 71.5% for CRC. Such low specificity of fecal M2-PK will lead to unacceptably high number of false positives if it is used for mass CRC screening, leading to unindicated colonoscopies with its associated inconveniences, risks and costs. CRC screening test must have high specificity; a high sensitivity is not as vital. To conclude, M2-PK was found to be a poor screening biomarker for CR neoplasia in a subject population at above average risk based on its prospective comparison with colonoscopy. These marginal performance characteristics do not permit its use as a screening tool for CR neoplasia in present clinical settings.

Noninvasive testing for colorectal cancer: a review

OBJECTIVES

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Endoscopic screening is now in favor and its use is increasing, but overall participation rates are poor. A substantial percentage of the population will likely continue to resist endoscopic screening. As such, a noninvasive biomarker for the early detection of CRC remains a priority. Herein, we (i) review the currently available noninvasive screening markers for the early detection of CRC, (ii) discuss newer markers that have undergone preliminary testing, and (iii) introduce and explain potentially promising markers of the future.

METHODS

The published literature on markers for early detection of CRC was identified using a MEDLINE/PubMed search with secondary review of cited publications.

RESULTS

Noninvasive testing for CRC is most advanced in testing for stool fecal occult blood, globin, or DNA mutations. Study of abnormal mucins has also been explored. Research for serum-based markers is just beginning and includes serum proteomics, nuclear matrix proteins, and serum DNA testing.

CONCLUSIONS

Serial guaiac-based fecal occult blood testing (FOBT) is simple, inexpensive, and proven effective at reducing mortality from CRC. Immunochemical fecal occult blood tests facilitate compliance and offer improved specificity, but at increased cost in comparison to FOBT. Fecal DNA testing may provide enhanced sensitivity for detection of CRC in comparison with FOBT, but its high cost limits its use for generalized screening. Rectal mucin testing requires additional evaluation to determine its sensitivity and specificity in comparison with guaiac-based FOBT. Serum tests, such as proteomics, nuclear matrix proteins, and serum DNA, are still in their infancy, but remain a hope for the future.