Molecular tests for colorectal cancer screening

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

Molecular approaches to stool screening for colorectal cancer

Detection of molecular markers of colorectal neoplasia in feces provides innovative, noninvasive means to screen for colorectal cancer and adenomas. Molecular markers, de.ned as a specific molecule or molecular structure, reach the gut lumen by the processes of leakage, secretion, cell exfoliation, or a combination of these processes. Exfoliated cells are the most likely to be specific for neoplasia. Fecal molecular markers will serve as the noninvasive first test in two-step screening for colorectal cancer, in which the second test is colonoscopy. This first step separates people into two categories: those more likely to have neoplasia and those less likely. Any new test should therefore be an improvement over the proven, but only modestly effective, guaiac-based fecal occult blood tests. The leakage marker hemoglobin can now be accurately detected by fecal immunochemical tests (FIT) for hemoglobin. These tests perform better than guaiac tests in specificity, sensitivity, and subject participation. Secreted mucins have inadequate specificity. Multitarget fecal DNA tests for exfoliated cells have not achieved their potential and have not been shown to be an improvement over FIT.     

Noninvasive diagnostic modalities for early detection of colorectal cancer

Colorectal cancer (CRC) screening strategies currently approved are colonoscopy every 10 years, annual fecal occult blood testing (FOBT), flexible sigmoidoscopy every 5 years, annual FOBT plus flexible sigmoidoscopy, and double-contrast barium enema every 5 years. Colonoscopy has been shown to be preferable, but it is invasive, needs bowel preparation, entails a risk of perforation, and is highly operator-dependent. Several noninvasive strategies are being developed as alternatives to colonoscopy. CT colonography (CTC), also known as virtual colonoscopy, has widely variable results but has been shown to have acceptable cost-effectiveness at either 5-year or 10-year intervals, whether it is performed using two-dimensional or three-dimensional techniques. Fecal immunochemical tests have now been shown to have clearly superior performance compared with guaiac-based testing and may become the FOBT of choice. Stool DNA (sDNA) testing has been improved by the addition to the commercial assay of gel-based DNA capture and buffering solutions for DNA stabilization. Simplified sDNA assays (for vimentin methylation and long DNA only) may also improve sensitivity. Advances in our understanding of the molecular genetic changes involved in neoplastic transformation have led to new noninvasive methods to detect tumors. The future of CRC screening will be driven by the performance characteristics of these technologies, which will be more clearly understood as additional data emerge.     

Advance in plasma SEPT9 gene methylation assay for colorectal cancer early detection

This review article summarizes the research advances of the plasma-based SEPT9 gene methylation assay for the clinical detection of colorectal cancer and its limitations. Colorectal cancer is a common malignancy with a poor prognosis and a high mortality, for which early detection and diagnosis are particularly crucial for the high-risk groups. Increasing evidence supported that SEPT9 gene methylation is associated with the pathogenesis of colorectal cancer and that detecting the level of methylation of SEPT9 in the peripheral blood can be used for screening of colorectal cancer in susceptible populations. In recent years, the data obtained in clinical studies demonstrated that the SEPT9 gene methylation assay has a good diagnostic performance with regard to both sensitivity and specificity with the advantage of better acceptability, convenience and compliance with serological testing compared with fecal occult blood tests and carcinoembryonic antigen for colorectal cancer (CRC). Furthermore, the combination of multiple methods or markers has become a growing trend for CRC detection and screening. Nevertheless, the clinical availability of the methylated SEPT9 assay is still limited because of the large degree of sample heterogeneity caused by demographic characteristics, pathological features, comorbidities and/or technique selection. Another factor is the cost-effectiveness of colorectal cancer screening strategies that hinders its large-scale application. In addition, improvements in its accuracy in detecting adenomas and premalignant polyps are required.     

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.     

Low‐mass‐ion discriminant equation: A new concept for colorectal cancer screening

Blood metabolites can be detected as low‐mass ions (LMIs) by mass spectrometry (MS). These LMIs may reflect the pathological changes in metabolism that occur as part of a disease state, such as cancer. We constructed a LMI discriminant equation (LOME) to investigate whether systematic LMI profiling might be applied to cancer screening. LMI information including m/z and mass peak intensity was obtained by five independent MALDI‐MS analyses, using 1,127 sera collected from healthy individuals and cancer patients with colorectal cancer (CRC), breast cancer (BRC), gastric cancer (GC) and other types of cancer. Using a two‐stage principal component analysis to determine weighting factors for individual LMIs and a two‐stage LMI selection procedure, we selected a total of 104 and 23 major LMIs by the LOME algorithms for separating CRC from control and rest of cancer samples, respectively. CRC LOME demonstrated excellent discriminating power in a validation set (sensitivity/specificity: 93.21%/96.47%). Furthermore, in a fecal occult blood test (FOBT) of available validation samples, the discriminating power of CRC LOME was much stronger (sensitivity/specificity: 94.79%/97.96%) than that of the FOBT (sensitivity/specificity: 50.00%/100.0%), which is the standard CRC screening tool. The robust discriminating power of the LOME scheme was reconfirmed in screens for BRC (sensitivity/specificity: 92.45%/96.57%) and GC (sensitivity/specificity: 93.18%/98.85%). Our study demonstrates that LOMEs might be powerful noninvasive diagnostic tools with high sensitivity/specificity in cancer screening. The use of LOMEs could potentially enable screening for multiple diseases (including different types of cancer) from a single sampling of LMI information.     

A higher detection rate for colorectal cancer and advanced adenomatous polyp for screening with immunochemical fecal occult blood test than guaiac fecal occult blood test,despite lower compliance rate. A prospective,controlled, feasibility study

Immunochemical fecal occult blood test (FIT) is a new colorectal cancer (CRC) screening method already recommended by the American screening guidelines. We aimed to test the feasibility of FIT as compared to guaiac fecal occult blood test (G‐FOBT) in a large urban population of Tel Aviv. Average‐risk persons, aged 50–75 years, were offered FIT or G‐FOBT after randomization according to the socioeconomic status of their clinics. Participants with positive tests underwent colonoscopy. Participants were followed through the Cancer Registry 2 years after the study. Hemoccult SENSA? and OC‐MICRO? (three samples, 70 ng/ml threshold) were used. FIT was offered to 4,657 persons (Group A) and G‐FOBT to 7,880 persons (Group B). Participation rate was 25.9% and 28.8% in Group A and B, respectively (p < 0.001). Positivity rate in Group A and B was 12.7% and 3.9%, respectively (p < 0.001). Cancer found in six (0.49%) and eight (0.35%) patients of Group A and B, respectively (NS). Cancer registry follow‐up found missed cancer in five (0.22%) cases of Group B and none in Group A (NS). The sensitivity, specificity, negative and positive predictive value for cancer in Group A and B were 100%, 85.9%, 100%, 3.9% and 61.5%, 96.4%, 99.8%, 9.1%, respectively. There was increased detection of advanced adenomatous polyp (AAP) by FIT, irrespective of age, gender, and socioeconomic status (Per Protocol: odds ratio 2.69, 95% confidence interval 1.6–4.5; Intention to Screen: odds ratio 3.16, 95% confidence interval 1.8–5.4). FIT is feasible in urban, average‐risk population, which significantly improved performance for detection of AAP and CRC, despite reduced participation.     

Multitarget stool DNA for colorectal cancer screening: A review and commentary on the United States Preventive Services Draft Guidelines

Multitarget stool DNA (mt-sDNA) testing was approved for average risk colorectal cancer (CRC) screening by the United States Food and Drug Administration and thereafter reimbursed for use by the Medicare program (2014). The United States Preventive Services Task Force (USPSTF) October 2015 draft recommendation for CRC screening included mt-sDNA as an “alternative” screening test that “may be useful in select clinical circumstances”, despite its very high sensitivity for early stage CRC. The evidence supporting mt-sDNA for routine screening use is robust. The clinical efficacy of mt-sDNA as measured by sensitivity, specificity, life-years gained (LYG), and CRC deaths averted is similar to or exceeds that of the other more specifically recommended screening options included in the draft document, especially those requiring annual testing adherence. In a population with primarily irregular screening participation, tests with the highest point sensitivity and reasonable specificity are more likely to favorably impact CRC related morbidity and mortality than those depending on annual adherence. This paper reviews the evidence supporting mt-sDNA for routine screening and demonstrates, using USPSTF’s modeling data, that mt-sDNA at three-year intervals provides significant clinical net benefits and fewer complications per LYG than annual fecal immunochemical testing, high sensitivity guaiac based fecal occult blood testing and 10-year colonoscopy screening.     

Screening for colorectal neoplasias with fecal occult blood tests: false-positive impact of non-dietary restriction

Objective: Screening for colorectal cancer using guaiac-based fecal occult blood tests (gFOBT) is wellestablished in Western populations, but is hampered by poor patient compliance due to the imposed dietaryrestrictions. Fecal immunochemical tests (FIT) do not require dietary restriction, but are more expensive thangFOBT and therefore restrict its use in developing countries in Asia. However, Asian diets being low in meatcontent may not require diet restriction for gFOBT to achieve equivalent results. The objective of this study wasto evaluate and compare the validity and suitability of gFOBT and FIT or a combination of the two in screeningfor colorectal neoplasias without prior dietary restriction in an Asian population. Methods: Patients referred tothe Endoscopic Unit for colonoscopy were recruited for the study. Stool samples were collected prior to bowelpreparation, and tested for occult blood with both gFOBT and FIT. Dietary restriction was not imposed. Toassess the validity of either tests or in combination to detect a neoplasm or cancer in the colon, their false positiverates, their sensitivity (true positive rate) and the specificity (true negative rate) were analyzed and compared.Results: One hundred and three patients were analysed. The sensitivity for picking up any neoplasia was 53%for FIT, 40% for gFOBT and 23.3% for the combination. The sensitivities for picking up only carcinoma were77.8% , 66.7% and 55.5%, respectively. The specificity for excluding any neoplasia was 91.7% for FIT, 74% forgFOBT and 94.5% for a combination, whereas for excluding only carcinomas they were 84%, 73.4% and 93.6%.Of the 69 with normal colonoscopic findings, FOBT was positive in 4.3%, 23.2 %and 2.9% for FIT, gFOBT, orcombination of tests respectively. Conclusion: FIT is the recommended method if we are to dispense with dietaryrestriction in our patients because of its relatively low-false positivity and better sensitivity and specificity rates.     

Development of new non‐invasive tests for colorectal cancer screening: The relevance of information on adenoma detection

Researchers are actively pursuing the development of a new non‐invasive test (NIT) for colorectal cancer (CRC) screening as an alternative to fecal occult blood tests (FOBTs). The majority of pilot studies focus on the detection of invasive CRC rather than precursor lesions (i.e., adenomas). We aimed to explore the relevance of adenoma detection for the viability of an NIT for CRC screening by considering a hypothetical test that does not detect adenomas beyond chance. We used the Simulation Model of Colorectal Cancer (SimCRC) to estimate the effectiveness of CRC screening and the lifetime costs (payers' perspective) for a cohort of US 50‐years‐old persons to whom CRC screening is offered from age 50–75. We compared annual screening with guaiac and immunochemical FOBTs (with sensitivities up to 70 and 24% for CRC and adenomas, respectively) to annual screening with a hypothetical NIT (sensitivity of 90% for CRC, no detection of adenomas beyond chance, specificity and cost similar to FOBTs). Screening with the NIT was not more effective, but was 29–44% more costly than screening with FOBTs. The findings were robust to varying the screening interval, the NIT's sensitivity for CRC, adherence rates favoring the NIT, and the NIT's unit cost. A comparative modelling approach using a model that assumes a shorter adenoma dwell time (MISCAN‐COLON) confirmed the superiority of the immunochemical FOBT over an NIT with no ability to detect adenomas. Information on adenoma detection is crucial to determine whether a new NIT is a viable alternative to FOBTs for CRC screening. Current evidence thus lacks an important piece of information to identify marker candidates that hold real promise and deserve further (large‐scale) evaluation.     

Fecal immunochemical test accuracy in familial risk colorectal cancer screening

There is little information on fecal immunochemical test (FIT) in familial risk colorectal cancer (CRC) screening. Our study assesses FIT accuracy, number needed to scope (NNS) and cost to detect a CRC and an advanced neoplasia (AN) in this setting. We performed a multicentric, prospective, double‐blind study of diagnostic tests on individuals with first‐degree relatives (FDRs) with CRC submitted to screening colonoscopy. Two stool samples were collected and fecal hemoglobin in the first sample (FIT1) and the highest in both samples (FITmax) were determined. Areas under the curve (AUC) for CRC and AN as well as the best FIT1 and FITmax cutoff value for CRC were determined. At this threshold, NNS and the cost per lesion detected were calculated. A total of 595 individuals were included (one FDR > 60 years, 413; two FDR or one ≤ 60 years, 182). AN and CRC were found in 64 (10.8%) and six (1%) patients, respectively. For CRC diagnosis, FIT1 AUC was 0.96 [95% confidence interval (CI): 0.95–0.98] and FITmax AUC was 0.95 (95% CI: 0.93–0.97). For AN diagnosis, FIT1 and FITmax AUC were 0.74 (95% CI: 0.66–0.82). The best cutoff point for CRC was 115. At this threshold, the NNS to detect a CRC was 5.67 and 7.67, and the cost per CRC was 1,064€ and 1591.33€ on FIT1 and FITmax strategies, respectively. FIT shows high accuracy to detect CRC in familial CRC screening. Performing two tests does not improve diagnostic accuracy, but increases cost and NNS to detect a lesion.     

Screening tests for colorectal cancer: A menu of options remains relevant

Until the early 1990s, no evidence was available to show that screening for colorectal cancer (CRC) by any means actually saved lives. Subsequently, sufficient evidence for the efficacy of fecal occult blood testing (FOBT) and flexible sigmoidoscopy allowed the US Preventive Services Task Force to publish guidelines for CRC screening. Since that time the major organizations in the United States concerned with screening guidelines have recommended a menu of screening test options including FOBT, flexible sigmoidoscopy, flexible sigmoidoscopy plus FOBT, barium enema, and colonoscopy. No organization, except for the American College of Gastroenterology, has designated any one of these options as “preferred.” Nevertheless, the lay press and many gastroenterology opinion leaders have encouraged Americans to have only one test—colonoscopy. In this review we discuss the rationale for caution in designating one screening test as “the best” and present information on how new stool and serum tests can be used effectively to screen for CRC.     

Determinants of colorectal cancer screening behavior among Chinese Americans

Colorectal cancer (CRC) is the most commonly diagnosed cancer among Chinese Americans and is the third leading cause of cancer death in this population. The objectives of this study were to determine the rates of CRC screening (via fecal occult blood test (FOBT), flexible sigmoidoscopy (FSIG), and colonoscopy) among Chinese Americans and predictors of utilizing these screening procedures. Participants (N = 206) completed a self-administered questionnaire assessing cancer screening behaviors and beliefs about perceived risk of developing cancer and treatment efficacy. A series of logistic regressions indicated that physician recommendation to obtain CRC screening significantly predicted whether Chinese Americans undergo FOBT, FSIG, or colonoscopy screening (p < 0.001). Acculturation and perceived risk of developing CRC did not predict obtaining any of the screening procedures. FOBT was the most commonly reported screening method used by respondents (65%), followed by FSIG (54%) and colonoscopy (49%). These findings highlight the need to make physicians more aware of the impact their recommendations have in determining CRC screening behavior among Chinese Americans.     

Current status of screening for colorectal cancer

BackgroundColorectal cancer (CRC) is a leading cause of cancer morbidity and mortality. A well-defined precursor lesion (adenoma) and a long preclinical course make CRC a candidate for screening. This paper reviews the current evidence for the most important tests that are widely used or under development for population-based screening.Material and methodsIn this narrative review, we scrutinized all papers we have been aware of, and carried out searches in PubMed and Cochrane library for relevant literature.ResultsTwo screening methods have been shown to reduce CRC mortality in randomised trials: repetitive faecal occult blood testing (FOBT) reduces CRC mortality by 16%; once-only flexible sigmoidoscopy (FS) by 28%. FS screening also reduces CRC incidence (by 18%), FOBT does not. Colonoscopy screening has a potentially larger effect on CRC incidence and mortality, but randomised trials are lacking. New screening methods are on the horizon but need to be tested in large clinical trials before implementation in population screening.ConclusionsFS screening reduces CRC incidence and CRC mortality by removal of adenomas; FOBT reduces CRC mortality by early detection of cancer. Several other tests are available, but none has been evaluated in randomised trials. Screening strategies differ considerably across countries.     

What is needed for colorectal cancer screening in Japan

There have been accumulated evidence with colorectal cancer(CRC)screening programs using the fecal occult blood test (FOBT). However, the purpose of CRC mortality reduction has not been attained as are the same with the other cancer screening programs in Japan. Thus the present issue with the CRC screening program is how we could reach the goal. Organized screening(OS), which is the strategy for reducing cancer mortality through screening, should be constructed in Japan for the purpose. Scientific evidence to reduce mortality is the prerequisite of OS. In addition, the second step required is to establish a quality assurance system or the management of the screening program, which can maximize the benefit and minimize the harms from screening. Finally, establishing a call-recall system enabling high participation rate is important. The above change may need an implementation of institutional reform on cancer screening in Japan.     

Validation of self-reported colorectal cancer screening behavior from a mixed-mode survey of veterans.

OBJECTIVE: The aim of the study was to validate self-reported colorectal cancer (CRC) screening using the National Cancer Institute Colorectal Cancer Screening questionnaire. MATERIALS AND METHODS: 890 patients, ages 50 to 75 years, from the Minneapolis Veterans Affairs (VA) Medical Center were surveyed by mail. Phone administration was attempted with mail nonresponders. VA and non-VA records were combined for the reference standard. Sensitivity, specificity, concordance, and report-to-records ratio (R2R) were estimated for overall and test-specific CRC adherence among respondents providing complete medical records. Secondary analyses examined variation in estimates by patient characteristics, treatment of missing and uncertain responses, and whether a strict or liberal time interval was used for assessing concordance. RESULTS: Complete medical records were available for 345 of the 686 survey responders. For overall adherence, sensitivity was 0.98, specificity was 0.59, concordance was 0.88, and R2R was 1.14. Sensitivity was 0.82 for fecal occult blood test (FOBT), 0.75 for sigmoidoscopy, 0.97 for colonoscopy, and 0.63 for double-contrast barium enema (DCBE). Specificity was 0.89 for FOBT, 0.76 for sigmoidoscopy, 0.72 for colonoscopy, and 0.85 for DCBE. Concordance was >0.80 for all tests other than sigmoidoscopy (0.76). R2R was 1.31 for FOBT, 1.33 for sigmoidoscopy, 1.42 for colonoscopy, and 6.13 for DCBE. The R2R was lower for a combined sigmoidoscopy and colonoscopy measure. Overreporting was more pronounced for older, less-educated individuals with no family history of CRC. Sensitivity and R2R improved using a liberal interval and treating uncertain responses as nonadherent (versus missing), but differences were not statistically significant. CONCLUSIONS: Self-reported CRC screening validity is generally acceptable and robust across definitional decisions, but varies by screening test and patient characteristics.     

Predictors of colorectal cancer screening from patients enrolled in a managed care health plan

BACKGROUND: Despite the growing recognition of the importance of colorectal cancer (CRC) screening in reducing cancer mortality, national screening rates are low, indicating a critical need to understand the barriers and remedies for underutilization of CRC screening tests. METHODS: Using results from independent cross-sectional telephone surveys with patients aged>or=50 years performed before (2000; n=498) and after (2003; n=482) a quality improvement intervention for CRC screening within a large managed care health plan, the trends and predictors of CRC screening with fecal occult blood test (FOBT) and/or endoscopy (flexible sigmoidoscopy/colonoscopy) were examined from a patient perspective. RESULTS: In 2000, patient reported screening rates within guidelines were 38% for any test, 23% for endoscopy, and 22% for FOBT. In 2003, screening rates increased to 50% for any test, 39% for endoscopy, and 24% for FOBT. Having discussed CRC with a doctor significantly increased the odds of being screened (FOBT: odds ratio [OR], 2.09 [95% confidence interval (95% CI), 1.47-2.96]; endoscopy: OR, 2.33 [95% CI, 1.67-3.26]; and any test: OR, 2.86 [95% CI, 2.06-3.96]), and reporting barriers to CRC in general decreased the odds of being screened (FOBT: OR, 0.76 [95% CI, 0.60-0.95]; endoscopy: OR, 0.74 [95% CI, 0.60-0.92]; and any test: OR, 0.66 [95% CI, 0.54-0.80]). CONCLUSIONS: Although screening rates increased over the 3-year period, evidence was found of ongoing underutilization of CRC screening. The 2 strongest determinants of obtaining CRC screening were provider influence and patient barriers related to CRC screening in general, pointing to the need for multilevel interventions that target both the provider and patient.     

Preferences for colorectal cancer screening tests and screening test use in a large multispecialty primary care practice

BACKGROUND:

The purpose of this study was to identify factors associated with colorectal cancer (CRC) screening test preference and examine the association between test preference and test completed.

METHODS:

Patients (n = 1224) were 50‐70 years, at average CRC risk, and overdue for screening. Outcome variables were preference for fecal occult blood test (FOBT), colonoscopy (COL), sigmoidoscopy (SIG), or barium enema (BE), measured by telephone survey, and concordance between test preference and test completed assessed using medical records.

RESULTS:

Thirty‐five percent preferred FOBT, 41.1% COL, 12.7% SIG, and 5.7% BE. Preference for SIG or COL was associated with having a physician recommendation, greater screening readiness, test‐specific self‐efficacy, greater CRC worry, and perceived pros of screening. Preference for FOBT was associated with self‐efficacy for doing FOBT. Participants who preferred COL were more likely to complete COL compared with those who preferred another test. Of those screened, only 50% received their preferred test. Those not receiving their preferred test most often received COL (52%).

CONCLUSIONS:

Lack of concordance between patient preference and test completed suggests that patients' preferences are not well incorporated into screening discussions and test decisions, which could contribute to low screening uptake. Physicians should acknowledge patients' preferences when discussing test options and making recommendations, which may increase patients' receptivity to screening. Cancer 2011. © 2011 American Cancer Society.     

Factors associated with false-positive fecal immunochemical tests in a large German colorectal cancer screening study

In recent years fecal immunochemical tests (FITs) have been offered as a primary screening test for colorectal cancer (CRC) in a growing number of countries. Our study aims to identify factors associated with apparently false-positive results of FITs. In this cross-sectional study within the German population-based screening colonoscopy program, participants were invited to provide a stool sample for FIT prior to colonoscopy. Four thousand six hundred and fifty six participants aged 50–79 years with no known history of CRC or inflammatory bowel disease (IBD) and no findings of neoplasms at screening colonoscopy were included in the current analyses. Main outcome measures were rates and factors associated with apparently false-positive FIT results. Apparently false-positive FIT results were found for 378 participants (8.1%). Male sex (OR = 1.30, 95%CI 1.03, 1.62), age ≥65 years (OR = 1.27, 95%CI 1.01, 1.59), a BMI ≥30 kg/m² (OR = 1.81, 95%CI 1.36, 2.40), current smoking (OR = 1.63, 95%CI 1.18, 2.25), use of aspirin (OR = 1.36, 95%CI 1.02, 1.82) and a new diagnosis of IBD (OR = 9.13, 95%CI 2.18, 38.19) or other non-neoplastic findings (OR = 1.86, 95%CI 1.37, 2.51) at screening colonoscopy were independently associated with significantly increased odds of a positive FIT. Although considered false positive in the context of CRC screening, the identified factors associated with apparently false-positive FIT results are known risk factors for and may point to conditions other than colorectal neoplasms that may be potential sources of gastrointestinal bleeding, potentially requiring further medical follow up.     

Analytical sensitivity and stability of DNA methylation testing in stool samples for colorectal cancer detection

Background

Stool-based molecular tests hold large potential for improving colorectal cancer screening. Here, we investigated the analytical sensitivity of a DNA methylation assay on partial stool samples, and estimated the DNA degradation in stool over time. In addition, we explored the detection of DNA methylation in fecal immunochemical test (FIT) fluid.

Materials and Methods

Partial stool samples of colonoscopy-negative individuals were homogenized with stool homogenization buffer, spiked with different numbers of HCT116 colon cancer cells and kept at room temperature for 0, 24, 48, 72 and 144?h before DNA isolation. Analytical sensitivity was determined by the lowest number of cells that yielded positive test results by DNA methylation or mutation analysis. DNA methylation in FIT fluid was measured in 11 CRC patients and 20 control subjects.

Results

The analytical sensitivity for detecting DNA methylation was 3000 cells per gram stool, compared to 60000 cells per gram stool for detection of DNA mutations in the same stool samples. No degradation up to 72?h was noted when a conservation buffer was used. DNA methylation was detected in 4/11 CRC FIT samples and in none of the 20 control FIT samples.

Conclusions

Methylation based stool DNA testing showed a high analytical sensitivity for tumor DNA in partial stool samples, which was hardly influenced by DNA degradation over time, provided an adequate buffer was used. The feasibility of detecting DNA methylation in FIT fluid demonstrates the opportunity to combine testing for occult blood with DNA methylation in the same collection device.