Screening CT Colonography Research Articles

For practice a high quality screening CT colonography

For practice a high quality screening CT colonography

The Challenges of CT Colonography Reimbursement

CT colonography has been shown to be an effective method to screen for colorectal cancer. However, at present, full endorsement and reimbursement for screening CT colonography, particularly by the US Preventive Services Task Force and CMS, respectively, are absent, so this screening option is infrequently used, and optical colonoscopy remains the de facto standard screening option. The authors summarize the past accomplishments that led to the current state of reimbursement and outline the remaining challenges and road to full acceptance and reimbursement of screening CT colonography nationally.

Abstract CN07-03: Natural history of small colorectal polyps at in vivo CT colonography surveillance

Abstract The clinical relevance and in-vivo growth rates of small (6–9 mm) colorectal polyps are not well established. We aimed to assess the behavior of such polyps with CT colonography assessments. In this longitudinal study, we enrolled asymptomatic adults undergoing routine colorectal cancer screening with CT colonography at two medical centers in the USA. Experienced investigators measured volumes and maximum linear sizes of polyps in vivo with CT colonography scans at baseline and surveillance follow-up. We defined progression, stability, and regression on the basis of a 20% volumetric change per year from baseline (20% or more growth classed as progression, 20% growth to –20% reduction classed as stable, and –20% or more reduction classed as regression). We compared findings with histological subgroups confirmed after colonoscopy when indicated. Between April, 2004, and June, 2012, we screened 22,006 asymptomatic adults and included 243 adults (mean age 57·4 years [SD 7·1] and median age 56 years [IQR 52–61]; 106 [37%] women), with 306 small colorectal polyps. The mean surveillance interval was 2.3 years (SD 1.4; range 1–7 years; median 2.0 years [IQR 1.1–2.3]). 68 (22%) of 306 polyps progressed, 153 (50%) were stable, and 85 (28%) regressed, including an apparent resolution in 32 (10%) polyps. We established immediate histology in 131 lesions on colonoscopy after final CT colonography. 21 (91%) of 23 proven advanced adenomas progressed, compared with 31 (37%) of 84 proven non-advanced adenomas, and 15 (8%) of 198 other lesions (p<0·0001). The odds ratio for a growing polyp at CT colonography surveillance to become an advanced adenoma was 15.6 (95% CI 7.6–31.7) compared with 6–9 mm polyps detected and removed at initial CT colonography screening (without surveillance). Mean polyp volume change was a 77% increase per year for 23 proven advanced adenomas and a 16% increase per year for 84 proven non-advanced adenomas, but a 13% decrease per year for all proven non-neoplastic or unresected polyps (p<0.0001). An absolute polyp volume of more than 180 mm3 at surveillance CT colonography identified proven advanced neoplasia (including one delayed cancer) with a sensitivity of 92% (22 of 24 polyps), specificity of 94% (266 of 282 polyps), positive-predictive value of 58% (22 of 38 polyps), and negative-predictive value of 99% (266 of 268 polyps). Only 16 (6%) of the 6–9 mm polyps exceeded 10 mm at follow-up. Volumetric growth assessment of small colorectal polyps serves as a useful biomarker for determination of clinical importance. Advanced adenomas show more rapid growth than non-advanced adenomas, whereas most other small polyps remain stable or regress. Our findings might allow for less invasive surveillance strategies, reserving polypectomy for lesions that show substantial growth. Further research is needed to provide more information regarding the ultimate fate of unresected small polyps without significant growth. Citation Format: Perry J. Pickhardt. Natural history of small colorectal polyps at in vivo CT colonography surveillance. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr CN07-03.

Applying Dose Reduction to CT Colonography

There is increasing awareness of the radiation dose delivered to patients using computed tomography (CT). It is important to properly manage the radiation dose when performing CT colonography (CTC) for colorectal cancer screening since the test may be repeated several times over the lifetime of the individual. There must be a balance of the overall benefit of screening CTC versus any theoretical risk of radiation. Technically there must also be a balance of radiation dose with image quality. Efforts continue to lower the radiation dose as much as possible while maintaining diagnostic accuracy for CTC in conjunction with overall national efforts by professional organizations, providers of medical imaging services, and equipment manufacturers. This article reviews the strategies that may be used to reduce the radiation dose for CTC including practical methods, modifications of specific CT parameters, and the use of new iterative reconstruction techniques.

Colonic Perforation during Screening CT Colonography

Colonic Perforation during Screening CT Colonography

CT Colongraphy as a Tool for Colorectal Cancer Screening in African American Patients

Purpose: Racial disparities in the presentation of colorectal cancer (CRC) have been well documented. African Americans (AA) have a higher incidence of CRC, are diagnosed at a later stage, and have a decreased survival when compared to Caucasians. One suggested reason for these differences is decreased utilization of the diagnostic modalities currently available. Computed Tomographic Colonography (CTC) has been suggested as a potential non-invasive tool for CRC screening. To date no studies have examined the utility of CTC in average risk CRC screening in AA patients. We aimed to examine the utility of CTC for average risk CRC screening in AA patients as well as rates of follow-up colonoscopy, after an abnormal exam. Methods: Data from 229 consecutive AA patients presenting from February 2007 until August 2012 for average risk CRC screening with CTC at a large city hospital, in Brooklyn, NY, was collected in a prospective study design. The data was analyzed for reason for referral, polyp detection rate (PDR), follow-up colonoscopy, and pathology. In addition to the overall PDR, particular rates for segments of the colon not previously visualized during prior incomplete colonoscopies were calculated to account for possible decreased PDR due to prior polypectomies. Results: The most common reason for referral for CTC was incomplete colonoscopy. The overall PDR for all patients was 8.7%. However, the verified adenoma detection rate, determined by subsequent colonoscopy with biopsy or polypectomy was much lower at 2.2%, as many of the patients failed to follow up with further workup (45% of those with polyps), or follow-up endoscopy failed to detect adenomas (30%). Median time to follow-up colonoscopy was 188 days. By segment of previously unvisualized colon, there were 169 segments of ascending colon/cecum in which 5 polyps (3.0%) were noted, 115 segments of transverse colon in which no polyps were noted, 89 segments of descending colon in which 1 polyp (1.1%) was noted, 74 segments of sigmoid colon in which 2 polyps (2.7%) were noted, and 66 segments of rectum in which no polyps were noted. None of these polyps have yet been confirmed as adenomatous. In the 171 incomplete colonoscopies that were followed by CTC, 7 polyps were visualized on CTC after not being seen on colonoscopy, however, only 2 of them have been confirmed to be adenomatous. Conclusion: While CTC would seem to be an attractive potential CRC screening modality in AA patients, low rates of adenoma detection, and suboptimal follow-up seem to limit its utility. While the reasons for low PDR are not clear, polyp location and morphology in this subset of patients may partially account for these findings.

Evaluating patients' preferences for type of bowel preparation prior to screening CT colonography: Convenience and comfort versus sensitivity and specificity

To explore the relative value patients place on comfort and convenience versus test sensitivity and specificity in the context of computed tomographic colonography (CTC) screening. Twenty semi-structured interviews were carried out with patients attending hospital for radiological tests unrelated to CTC. Preferences for CTC with different types of bowel preparation for CTC screening were examined and interviews were analysed thematically. The discussion guide included separate sections on CTC, bowel preparation methods (non-, reduced- and full-laxative), and sensitivity and specificity. Patients were given information on each topic in turn and asked about their views and preferences during each section. Following information about the test, patients' attitudes towards CTC were positive. Following information on bowel preparation, full-laxative purgation was anticipated to cause more adverse physical and lifestyle effects than using reduced- or non-laxative preparation. However, stated preferences were approximately equally divided, largely due to patients anticipating that non-laxative preparations would reduce test accuracy (because the bowel was not thoroughly cleansed). Following information on sensitivity and specificity (which supported patients' expectations), the predominant stated preference was for full-laxative preparation. Patients are likely to value test sensitivity and specificity over a more comfortable and convenient preparation. Future research should test this hypothesis on a larger sample.

The Time Has Arrived for National Reimbursement of Screening CT Colonography

CT colonography (CTC) has been fully validated as an accurate screening test for colorectal carcinoma and is being disseminated globally. There is an abundance of new literature addressing the prior concerns of the U.S. Preventive Services Task Force and the Centers for Medicare & Medicaid Services. Specific areas related to radiation dose, extracolonic findings, and generalizability of CTC to senior patients are discussed. The time has arrived for national reimbursement of CTC in the United States.

Computed tomographic colonography for colorectal cancer screening

BACKGROUNDThe objective of this study was to determine whether age, sex, a positive family history of colorectal cancer, and body mass index (BMI) are important predictors of advanced neoplasia in the setting of screening computed tomographic colonography (CTC).METHODSConsecutive patients who were referred for first‐time screening CTC from 2004 to 2011 at a single medical center were enrolled. Results at pathology were recorded for all patients who underwent polypectomy. Logistic regression was used to identify significant predictor variables for advanced neoplasia (any adenoma ≥10 mm or with villous component, high‐grade dysplasia, or adenocarcinoma). Odds ratios (ORs) were used to express associations between the study variables (age, sex, BMI, and a positive family history of colorectal cancer) and advanced neoplasia.RESULTSIn total, 7620 patients underwent CTC screening. Of these, 276 patients (3.6%; 95% confidence interval [CI], 3.2%‐4.1%) ultimately were diagnosed with advanced neoplasia. At multivariate analysis, age (mean OR per 10‐year increase, 1.8; 95% CI, 1.6‐2.0) and being a man (OR, 1.7; 95% CI, 1.3‐2.2) were independent predictors of advanced neoplasia, whereas BMI and a positive family history of colorectal cancer were not. The number needed to screen to detect 1 case of advanced neoplasia varied from 51 among women aged ≤55 years to 10 among men aged >65 years. The number of post‐CTC colonoscopies needed to detect 1 case of advanced neoplasia varied from 2 to 4.CONCLUSIONSAge and sex were identified as important independent predictors of advanced neoplasia risk in individuals undergoing screening CTC, whereas BMI and a positive family history of colorectal cancer were not. These results have implications for appropriate patient selection. Cancer 2013;119:2549–2554. © 2013 American Cancer Society.

Assessment of volumetric growth rates of small colorectal polyps with CT colonography: a longitudinal study of natural history

The clinical relevance and in-vivo growth rates of small (6-9 mm) colorectal polyps are not well established. We aimed to assess the behaviour of such polyps with CT colonography assessments. In this longitudinal study, we enrolled asymptomatic adults undergoing routine colorectal cancer screening with CT colonography at two medical centres in the USA. Experienced investigators (PJP, DHK, JLH) measured volumes and maximum linear sizes of polyps in vivo with CT colonography scans at baseline and surveillance follow-up. We defined progression, stability, and regression on the basis of a 20% volumetric change per year from baseline (20% or more growth classed as progression, 20% growth to -20% reduction classed as stable, and -20% or more reduction classed as regression). We compared findings with histological subgroups confirmed after colonoscopy when indicated. This study is registered with ClinicalTrials.gov, number NCT00204867. Between April, 2004, and June, 2012, we screened 22,006 asymptomatic adults and included 243 adults (mean age 57·4 years [SD 7·1] and median age 56 years [IQR 52-61]; 106 [37%] women), with 306 small colorectal polyps. The mean surveillance interval was 2·3 years (SD 1·4; range 1-7 years; median 2·0 years [IQR 1·1-2·3]). 68 (22%) of 306 polyps progressed, 153 (50%) were stable, and 85 (28%) regressed, including an apparent resolution in 32 (10%) polyps. We established immediate histology in 131 lesions on colonoscopy after final CT colonography. 21 (91%) of 23 proven advanced adenomas progressed, compared with 31 (37%) of 84 proven non-advanced adenomas, and 15 (8%) of 198 other lesions (p<0·0001). The odds ratio for a growing polyp at CT colonography surveillance to become an advanced adenoma was 15·6 (95% CI 7·6-31·7) compared with 6-9 mm polyps detected and removed at initial CT colonography screening (without surveillance). Mean polyp volume change was a 77% increase per year for 23 proven advanced adenomas and a 16% increase per year for 84 proven non-advanced adenomas, but a 13% decrease per year for all proven non-neoplastic or unresected polyps (p<0·0001). An absolute polyp volume of more than 180 mm(3) at surveillance CT colonography identified proven advanced neoplasia (including one delayed cancer) with a sensitivity of 92% (22 of 24 polyps), specificity of 94% (266 of 282 polyps), positive-predictive value of 58% (22 of 38 polyps), and negative-predictive value of 99% (266 of 268 polyps). Only 16 (6%) of the 6-9 mm polyps exceeded 10 mm at follow-up. Volumetric growth assessment of small colorectal polyps could be a useful biomarker for determination of clinical importance. Advanced adenomas show more rapid growth than non-advanced adenomas, whereas most other small polyps remain stable or regress. Our findings might allow for less invasive surveillance strategies, reserving polypectomy for lesions that show substantial growth. Further research is needed to provide more information regarding the ultimate fate of unresected small polyps without significant growth. US National Institutes of Health, National Cancer Institute.

Predictors of CT Colonography Utilization Among Asymptomatic Medicare Beneficiaries

Although the Centers for Medicare and Medicaid Services (CMS) denied coverage for screening computed tomography colonography (CTC) in March 2009, little is understood about whether CTC was targeted to the appropriate patient population prior to this decision. Evaluate patient characteristics and known relative clinical indications for screening CTC among patients who received CTC compared to optical colonoscopy (OC). Cross-sectional study of all 10,538 asymptomatic Medicare beneficiaries who underwent CTC between January 2007 and December 2008, compared to a cohort of 160,113 asymptomatic beneficiaries who underwent OC, matched on county of residence and year of examination. Patient characteristics and known relative appropriate and inappropriate clinical indications for screening CTC. CTC utilization was higher among women, patients > 65years of age, white patients, and those with household income > 75% (p = 0.001). Patients with relatively appropriate clinical indications for screening CTC were more likely to undergo CTC than OC including presumed incomplete OC (OR 80.7, 95 % CI 76.01-85.63); sedation risk (OR 1.11, 95 % CI 1.05-1.17); and chronic anticoagulation risk (OR 1.46, 95 % CI 1.38-1.54), after adjusting for patient characteristics and known clinical indications. Conversely, patients undergoing high-risk screening, an inappropriate indication, were less likely to receive CTC (OR 0.4, 95 % CI 0.37-0.42). Overall, 83% of asymptomatic patients referred to CTC had at least one clinical indication relatively appropriate for CTC (8,772/10,538). During the 2years preceding CMS denial for screening, CTC was targeted to asymptomatic patients with relatively appropriate clinical indications for CTC/not receiving OC. However, CTC utilization was lower among certain demographic groups, including minority patients. These findings raise the possibility that future coverage of screening CTC might exacerbate disparities in colorectal cancer screening while increasing overall screening rates.

We screen newborns, don't we?: realizing the promise of public health genomics.

Genomics and public health have been uneasy bedfellows for some time. Most efforts to improve population health through genomic approaches have focused on the assessment of risks for common diseases, with the aim of tailoring interventions and screening.1 However, the improvement of population health through such an approach has remained elusive.2 Now, rapid progress in affordable, robust DNA sequencing offers a promising opportunity. By expanding the field’s focus from common to rare diseases, it may be possible to realize the promise of public health genomics by identifying those millions of individuals who unknowingly carry mutations that confer a dramatic predisposition to preventable diseases.

Variation in Diagnostic Performance among Radiologists at Screening CT Colonography

To assess the variation in diagnostic performance among radiologists at screening computed tomographic (CT) colonography. In this HIPAA-compliant, institutional review board-approved study, 6866 asymptomatic adults underwent first-time CT colonographic screening at a single center between January 2005 and November 2011. Results of examinations were interpreted by one of eight board-certified abdominal radiologists (mean number of CT colonographic studies per reader, 858; range, 131-2202). Findings at CT colonography and subsequent colonoscopy were recorded, and key measures of diagnostic performance, including adenoma and advanced neoplasia detection rate, were compared among the radiologists. The overall prevalence of histopathologically confirmed advanced neoplasia was 3.6% and did not differ significantly among radiologists (range, 2.4%-4.4%; P = .067; P = .395 when one outlier was excluded). Overall, 19.5% of polyps detected at CT colonography proved to be advanced neoplasia and did not differ significantly among radiologists (range, 14.4%-23.2%; P = .223). The overall per-polyp endoscopic confirmation rate was 93.5%, ranging from 80.0% to 97.6% among radiologists (P = .585). The overall percentage of nondiagnostic CT colonographic examinations was 0.7% and was consistent among radiologists (range, 0.3%-1.1%; P = .509). Consistent performance for adenoma and advanced neoplasia detection, as well as other clinically relevant end points, were observed among radiologists at CT colonographic screening.

Time requirements and health effects of participation in colorectal cancer screening with colonoscopy or computed tomography colonography in a randomized controlled trial

Time limitations and unwanted health effects may act as barriers to participation in colorectal cancer (CRC) screening. The aim of the study was to measure the time requirements and health effects of colonoscopy and computed tomography colonography (CTC) screening. This was a prospective diary study in a consecutive sample within a randomized controlled CRC screening trial, comparing primary colonoscopy and CTC screening for average-risk individuals aged 50 - 74 years. The diary ended when all screening-related complaints had passed. The diary was returned by 75 % (241/322) of colonoscopy and 75 % (127/170) of CTC screenees. The median interval between leaving home and returning from the examination was longer for colonoscopy (4 hours and 18 minutes [4:18], interquartile range [IQR] 3:30 - 5:00) than for CTC (2:30 hours, IQR 2:06 - 3:00; P < 0.001). Similarly, the time to return to routine activities was longer after colonoscopy (3:54 hours, IQR 1:48 - 15:00) than after CTC (1:36 hours, IQR 0:54 - 4:42). The duration of screening-related symptoms after the examination was shorter for colonoscopy (11:00 hours, IQR 2:54 - 20:00) than for CTC (22:00 hours; IQR 5:30 - 47:00; P < 0.001). Abdominal complaints were reported more frequently after CTC. Anxiety, pain, and quality of life worsened during the screening process, with no differences between the two examinations. Compared with colonoscopy, CTC screening required less time and allowed screenees to return to their daily activities more quickly. In contrast, CTC was associated with a twofold longer duration of screening-related symptoms. Feelings of anxiety, pain, and quality of life scores were similar during colonoscopy and CTC screening. These results should be incorporated into cost-effectiveness analyses of CRC screening techniques.

Informed decision-making in colorectal cancer screening using colonoscopy or CT-colonography

ObjectiveTo evaluate the level of informed decision making in a randomized controlled trial comparing colonoscopy and CT-colonography for colorectal cancer screening. Methods8844 citizens aged 50–75 were randomly invited to colonoscopy (n=5924) or CT-colonography (n=2920) screening. All invitees received an information leaflet. Screenees received a questionnaire within 4 weeks before the planned examination, non-screenees 4 weeks after the invitation. A decision was categorized as informed when characterized by sufficient decision-relevant knowledge and consistent with personal attitudes toward participation in screening. ResultsKnowledge and attitude items were completed by 1032/1276 colonoscopy screenees (81%), by 698/4648 colonoscopy non-screenees (15%), by 824/982 CT-colonography screenees (84%) and by 192/1938 CT-colonography non-screenees (10%). 1027 colonoscopy screenees (>99%) and 815 CT-colonography screenees (99%) had adequate knowledge; 915 (89%) and 742 (90%) had a positive attitude. 675 non-screenees invited to colonoscopy (97%) and 182 invited to CT-colonography (95%) had adequate knowledge; 344 (49%) and 94 (49%) expressed a negative attitude. ConclusionA large majority of screenees made an informed decision on participation. Almost half of responding non-screenees, made an uninformed decision, suggesting additional barriers to participation. Practice implicationsEfforts to understand the additional barriers will create opportunities to facilitate informed participation to colorectal cancer screening.

Clinical Use of CT Colonography for Colorectal Cancer Screening in Military Training Facilities and Potential Impact on HEDIS Measures

The National Committee for Quality Assurance developed the Healthcare Effectiveness Data and Information Set(®) (HEDIS(®)) to provide quality measures for the evaluation of standards of medical care across health plans. Screening for colorectal cancer (CRC) has been shown to increase the detection of early-stage disease and reduce mortality. Current HEDIS measures for CRC screening include fecal occult blood testing, flexible sigmoidoscopy, and colonoscopy. The aim of this analysis was to quantify the use of CT colonography (CTC) for CRC screening and demonstrate the potential impact of including CTC as a HEDIS-acceptable screening modality. Demographic and health care utilization data from the Military Health System Population Health Portal for January 1, 2005, through December 31, 2010, for individuals aged 50 to 75, were analyzed to determine the degree of overall utilization of CTC. Screening compliance for CRC per HEDIS was also estimated, and the incremental impact of adding HEDIS-eligible patients who had undergone CTC as their only CRC screening test was then evaluated for two similarly sized, regional Navy medical centers. Across all sites (10 Army, 4 Navy, 3 Air Force), 17,187 CTC studies were performed, with increasing utilization during the 6-year study period. At the two Navy medical centers, screening compliance ranged from 33.8% to 67.9% without CTC and from 33.8% to 84.0% with CTC. CTC is actively being used for CRC screening across military treatment facilities. The inclusion of CTC as a HEDIS-compliant CRC screening test has the potential to significantly increase health care system compliance for National Committee for Quality Assurance CRC screening measures.

Current Status and Future Prospect of CT colonography for Colorectal Cancer Screening

Current Status and Future Prospect of CT colonography for Colorectal Cancer Screening

Advances in CT Colonography for Colorectal Cancer Screening and Diagnosis

CT colonography (CTC) is a validated colorectal cancer test that provides an additional minimally-invasive screening option which is likely to be preferred by some patients. Important examination prerequisites include adequate colonic cleansing and distention. Tagging of residual material aids in the differentiation of true polyps from stool. Low radiation dose technique should be employed routinely for screening studies. Readers must be skilled in the use of both 2D and 3D interpretation methods.

Unit costs in population-based colorectal cancer screening using CT colonography performed in university hospitals in The Netherlands

Computed tomography (CT) colonography cost assumptions so far ranged from <euro>346 to <euro>594 per procedure, based on clinical CT reimbursement rates. The aim of our study was to estimate the costs in a screening situation. Data were collected within an invitational population-based CRC screening trial (n = 2,920, age 50-75 years) with a dedicated CT-screening setting. Unit costs were calculated per action, per invitee and per participant (depending on adherence) and per individual with detected advanced neoplasia. Sensitivity analyses were performed, and alternative scenarios were considered. Of the invitees, 47.2 % were reminded, 38.8 % scheduled for an intake, 37.2 % scheduled for CT colonography, 33.6 % underwent CT colonography and 1.1 % needed a re-examination. Lesions ≥ 10 mm were detected in 2.9 % of the invitees. Invitation costs were Euro 5.57. Costs per CT colonography (intake to results) were Euro 144.00. Extra costs of communication of positive results were Euro 9.00. Average costs of invitational-based CT colonography screening were Euro 56.97 per invitee, Euro 169.40 per participant and Euro 2,772.51 per individual with detected advanced neoplasia. Dutch costs of CT-screening were substantially lower than the cost assumptions that were used in published cost-effectiveness analyses on CT colonography screening. This finding indicates that previous cost-effectiveness analyses should be updated, at least for the Dutch situation.

COST-EFFECTIVENESS OF COMPUTED TOMOGRAPHY COLONOGRAPHY IN COLORECTAL CANCER SCREENING: A SYSTEMATIC REVIEW

The European Code Against Cancer recommends individuals aged ≥ 50 should participate in colorectal cancer screening. CT-colonography (CTC) is one of several screening tests available. We systematically reviewed evidence on, and identified key factors influencing, cost-effectiveness of CTC screening. PubMed, Medline, and the Cochrane library were searched for cost-effectiveness or cost-utility analyses of CTC-based screening, published in English, January 1999 to July 2010. Data was abstracted on setting, model type and horizon, screening scenario(s), comparator(s), participants, uptake, CTC performance and cost, effectiveness, ICERs, and whether extra-colonic findings and medical complications were considered. Sixteen studies were identified from the United States (n = 11), Canada (n = 2), and France, Italy, and the United Kingdom (1 each). Markov state-transition (n = 14) or microsimulation (n = 2) models were used. Eleven considered direct medical costs only; five included indirect costs. Fourteen compared CTC with no screening; fourteen compared CTC with colonoscopy-based screening; fewer compared CTC with sigmoidoscopy (8) or fecal tests (4). Outcomes assessed were life-years gained/saved (13), QALYs (2), or both (1). Three considered extra-colonic findings; seven considered complications. CTC appeared cost-effective versus no screening and, in general, flexible sigmoidoscopy and fecal occult blood testing. Results were mixed comparing CTC to colonoscopy. Parameters most influencing cost-effectiveness included: CTC costs, screening uptake, threshold for polyp referral, and extra-colonic findings. Evidence on cost-effectiveness of CTC screening is heterogeneous, due largely to between-study differences in comparators and parameter values. Future studies should: compare CTC with currently favored tests, especially fecal immunochemical tests; consider extra-colonic findings; and conduct comprehensive sensitivity analyses.