CT colonography for population screening: ready for prime time?

Evolving trends in CT colonography: A 10-year analysis of use and associated factors

PURPOSE

Computed tomographic colonography (CTC) is a non-invasive screening test for colorectal cancer (CRC) with high sensitivity and low risk of complications. We used a nationally representative sample of screening-eligible adults to examine trends in and factors associated with CTC use.

METHODS

We examined CTC use among 58,058 adults in the National Health Interview Survey in 2010, 2015, 2018, 2019, and 2021. For each survey year, we estimated CTC use by sociodemographic and health factors. We used multivariable logistic regression to identify factors associated with CTC use.

RESULTS

A total of 1.7 % adults reported receiving CTC across all survey years. CTC use was similar in 2010 (1.3 %), 2015 (0.8 %), 2018 (1.4 %), and 2019 (1.4 %) but increased in 2021 (3.5 %, p < 0.05). In multivariable analysis, survey year 2021 [vs. 2010, odds ratio (OR) 2.51, 95 % confidence interval (CI) 1.83-3.43], Hispanic (OR 1.73, 95 % CI 1.34-2.23), non-Hispanic Black (OR 2.07, 95 % CI 1.67-2.57), and household income <200 % federal poverty level (vs. >400 %, OR 1.25, 95 % CI 1.01-1.57) was associated with CTC use. Further, adults with a history of diabetes (OR 1.20, 95 % CI 1.01-1.45), chronic obstructive pulmonary disease (OR 1.58, 95 % CI 1.25-1.99), cancer (OR 1.29, 95 % CI 1.05-1.58), or past-year hospital admissions (OR 1.44, 95 % CI 1.18-1.78) were more likely to receive CTC.

CONCLUSION

CTC use remained low from 2010 to 2019 but increased in 2021. CTC use was more frequent among adults with chronic health conditions, minorities, and adults with lower income, and may help reduce disparities in CRC screening.

Comparison of MiraLAX and magnesium citrate for bowel preparation at CT colonography

PURPOSE

To compare MiraLAX, a hypo-osmotic lavage, and magnesium citrate (MgC), a hyper-osmotic agent for bowel preparation at CTC.

METHODS

398 total screening CTC studies were included in this retrospective, single institution study. 297 underwent preparation with a double-dose MgC regimen (mean age, 61 ± 5.5 years; 142 male/155 female) and 101 with 8.3 oz (equivalent to 238 g PEG) of MiraLAX (mean age, 60 ± 9.6 years; 45 male/56 female). Oral contrast for tagging purposes was utilized in both regimens. Studies were retrospectively analyzed for residual fluid volume and attenuation by automated analysis, as well for subjective oral contrast coating of the normal colonic wall and polyps. 50 patients underwent successive CTC studies utilizing each agent (mean, 6.1 ± 1.7 years apart), allowing for intra-patient comparison. Chi-squared, Fisher's exact, McNemar, and t-tests were used for data comparison.

RESULTS

Residual fluid volume (as percentage of total colonic volume) and fluid density was 7.2 ± 4.2% and 713 ± 183 HU for the MgC cohort and 8.7 ± 3.8% and 1044 HU ± 274 for the MiraLAX cohort, respectively (p = 0.001 and p < 0.001, respectively). Similar results were observed for the intra-patient cohort. Colonic wall coating negatively influencing interpretation was noted in 1.7% of MgC vs. 6.9% of MiraLAX examinations (p = 0.008). Polyps were detected in 12% of all MgC vs. 16% of all MiraLAX CTCs (p = 0.29).

CONCLUSION

CTC bowel preparation with the hypo-osmotic MiraLAX agent appears to provide acceptable diagnostic quality that is comparable to the hyper-osmotic MgC agent, especially when factoring in patient safety and tolerance.

An AI-Based Colonic Polyp Classifier for Colorectal Cancer Screening Using Low-Dose Abdominal CT

Among the non-invasive Colorectal cancer (CRC) screening approaches, Computed Tomography Colonography (CTC) and Virtual Colonoscopy (VC), are much more accurate. This work proposes an AI-based polyp detection framework for virtual colonoscopy (VC). Two main steps are addressed in this work: automatic segmentation to isolate the colon region from its background, and automatic polyp detection. Moreover, we evaluate the performance of the proposed framework on low-dose Computed Tomography (CT) scans. We build on our visualization approach, Fly-In (FI), which provides "filet"-like projections of the internal surface of the colon. The performance of the Fly-In approach confirms its ability with helping gastroenterologists, and it holds a great promise for combating CRC. In this work, these 2D projections of FI are fused with the 3D colon representation to generate new synthetic images. The synthetic images are used to train a RetinaNet model to detect polyps. The trained model has a 94% f1-score and 97% sensitivity. Furthermore, we study the effect of dose variation in CT scans on the performance of the the FI approach in polyp visualization. A simulation platform is developed for CTC visualization using FI, for regular CTC and low-dose CTC. This is accomplished using a novel AI restoration algorithm that enhances the Low-Dose CT images so that a 3D colon can be successfully reconstructed and visualized using the FI approach. Three senior board-certified radiologists evaluated the framework for the peak voltages of 30 KV, and the average relative sensitivities of the platform were 92%, whereas the 60 KV peak voltage produced average relative sensitivities of 99.5%.

Predictors of CT Colonography Use: Results From the 2019 National Health Interview Cross-Sectional Survey

PURPOSE

CT colonography (CTC) is a minimally invasive screening test with high sensitivity for colonic polyps (>1 cm). Prior studies suggest that CTC utilization remains low. However, there are few studies evaluating recent CTC utilization and predictors of CTC utilization. Our purpose was to estimate recent nationwide CTC utilization and evaluate predictors of CTC utilization using 2019 nationally representative cross-sectional survey data.

METHODS

Participants between ages 50 and 75 without colorectal cancer history in the 2019 National Health Interview Survey cross-sectional data were included. Proportion of participants reporting utilization of CTC was estimated, accounting for complex survey design elements. Multiple variable logistic regression analyses evaluated predictors of CTC utilization. Analyses were conducted accounting for complex survey design elements to obtain valid estimates for the civilian, noninstitutionalized US population.

RESULTS

In all, 13,709 respondents were included, and 1.4% reported undergoing CTC, of whom 39.9% underwent CTC within the last year, 18.5% within the last 2 years, 13.0% within the last 3 years, 7.8% within the last 5 years, 11.2% within the last 10 years, and 9.6% underwent CTC 10 years ago or more. Multiple variable logistic regression analyses revealed that Hispanic (odds ratio 2.67, 95% confidence interval 1.66-4.29, P < .001) and Black (odds ratio 2.47, 95% confidence interval 1.60-3.82, P < .001) participants were more likely than White participants to undergo CTC.

CONCLUSION

Survey results suggest that nationwide utilization of CTC remains low. Black and Hispanic participants were more likely than White participants to report undergoing CTC. Promotion of CTC may reduce racial and ethnic disparities in colorectal cancer screening.

Public Health: Prevention

Nowadays, colorectal cancer prevention strategies play an essential role in reducing the incidence and mortality of the cases. A well-designed and establishment of the clinical pathway of screening programme needed in all country. Types of screening tools used may vary between the country with the use of FOBT and colonoscopy. The standard guideline related to screening programme such as for high-risk group should be emphasized more as compared to the low-risk group. The uptake of screening for CRC should be highlighted more as the program have showed a significantly reduction of the cases and mortality. The barrier of CRC screening uptake mainly due to poor awareness, discomfort, low physician recommendation, low socioeconomic and improper screening programme. Therefore others prevention strategies beside screening program such as health education and interactive intervention strategies need to be empower.

Diagnostic Performance of Multitarget Stool DNA and CT Colonography for Noninvasive Colorectal Cancer Screening

BackgroundMultitarget stool DNA (mt-sDNA) screening has increased rapidly since simultaneous approval by the U.S. Food and Drug Administration and Centers for Medicare and Medicaid Services in 2014, whereas CT colonography screening remains underused and is not covered by Centers for Medicare and Medicaid Services.PurposeTo report postapproval clinical experience with mt-sDNA screening for colorectal cancer (CRC) and compare results with CT colonography screening at the same center.Materials and MethodsIn this retrospective cohort study, asymptomatic adults underwent clinical mt-sDNA screening during a 5-year interval (2014-2019). Electronic medical records were searched to verify test results and document subsequent optical colonoscopy and histopathologic findings. A similar analysis was performed for CT colonography screening during a 15-year interval (2004-2019), with consideration of thresholds for positivity of both 6-mm and 10-mm polyp sizes. χ² or two-sample t tests were used for group comparisons.ResultsA total of 3987 asymptomatic adult patients (mean age, 64 years ± 9 [standard deviation]; 2567 women) underwent mt-sDNA screening and 9656 patients (mean age, 57 years ± 8; 5200 women) underwent CT colonography. Test-positive rates for mt-sDNA and for 6-mm- and 10-mm-threshold CT colonography were 15.2%, 16.4%, and 6.7%, respectively. Optical colonoscopy follow-up rates for positive results of mt-sDNA and 6-mm- and 10-mm-threshold CT colonography were 13.1%, 12.3%, and 5.9%, respectively. Positive predictive values (PPVs) for any neoplasm 6 mm or greater, advanced neoplasia, and CRC for mt-sDNA were 54.2%, 22.7%, and 1.9% respectively; for 6-mm-threshold CT colonography, PPVs were 76.8%, 44.3%, and 2.7%; for 10-mm-threshold CT colonography, PPVs were 84.5%, 75.2%, and 5.2%, respectively (P < .001 for mt-sDNA vs CT colonography for all except 6-mm CRC at CT colonography). For mt-sDNA versus 6-mm-threshold CT colonography, overall detection rates for advanced neoplasia were 2.7% and 5.0%, respectively (P < .001); corresponding detection rates for CRC were 0.23% and 0.31%, respectively (P = .43).ConclusionThe detection rates of advanced neoplasia at CT colonography screening were greater than those of multitarget stool DNA. Detection rates were similar for colorectal cancer.© RSNA, 2020See also the editorial by Yee in this issue.

Positive Predictive Value for Colorectal Lesions at CT Colonography: Analysis of Factors Impacting Results in a Large Screening Cohort

OBJECTIVE. The purpose of this study is to evaluate factors affecting the positive predictive value (PPV) for detecting colorectal lesions at CT colonography (CTC), using optical colonoscopy (OC) as the reference standard for concordance. MATERIALS AND METHODS. Consecutive CTC studies from a single screening program interpreted as positive for at least one detected colorectal lesion 6 mm or larger and sent for subsequent OC were analyzed according to per-polyp and per-patient results. Univariable and multivariable analysis of multiple input factors was performed. RESULTS. Of 1650 studies (median patient age, 59.7 years; 877 men and 773 women) with 2688 total CTC-detected lesions 6 mm or larger, the overall PPVs were 88.8% (2386/2688) by polyp and 90.8% (1499/1650) by patient. The by-polyp PPV was significantly higher for polypoid (91.2%; 1793/1965) versus flat or nonpolypoid (79.4%; 459/578) lesions (p < 0.0001). Overall per-patient PPVs were 72.3% (1193/1650) for any neoplasia 6 mm or larger and 38.8% (641/1650) for advanced neoplasia. PPVs for advanced neoplasia increased by CTC Reporting and Data System category: 5.8% (45/781) for C2, 67.1% (511/762) for C3, and 79.4% (85/107) for C4. PPVs for cancer also increased by CTC Reporting and Data System category: 0% (0/781) for C2, 2.2% (17/762) for C3, and 52.3% (56/107) for C4. On multivariable regression analysis, polyp morphologic type (flat vs polypoid) and diagnostic confidence were the strongest predictors of CTC-OC concordance. CTC PPV results are somewhat underestimated because 28.8% (87/302) of CTC-OC-discordant results were categorized as likely OC false-negatives at consensus review. CONCLUSION. Concordance between CTC and OC is high for relevant colorectal polyps and masses. Unlike stool-based tests that provide only a binary positive or negative result, CTC can specify the nature of the positive findings, resulting in much greater specificity and risk stratification for patient management decisions.

Nationwide, Longitudinal Trends in CT Colonography Utilization: Cross-Sectional Survey Results From the 2010 and 2015 National Health Interview Survey

PURPOSE

Colon cancer screening reduces deaths from colorectal cancer. Screening rates have plateaued; however, studies have found that giving patients a choice between different screening tests improves adherence. CT colonography is a minimally invasive screening test with high sensitivity for colonic polyps (>1 cm). With increasing insurance coverage of CT colonography nationwide, there are limited estimates of CT colonography utilization over time. Our purpose was to estimate CT colonography utilization over time using nationally representative cross-sectional survey data.

METHODS

We utilized 2010 and 2015 National Health Interview Survey cross-sectional data. Participants between ages 50 and 75 without colorectal cancer history were included. Accounting for complex survey design elements, logistic regression analyses evaluated changes in CT colonography utilization over time, adjusted for potential confounders, and stratified by insurance and age.

RESULTS

Overall, 21,686 respondents were included (8,965 in 2010, 12,721 in 2015). Reported CT colonography utilization decreased from 1.2% to 0.9% (odds ratio [OR] 0.92, 95% confidence interval [CI] 0.86-0.98). Stratified analyses revealed no changes in utilization in patients with private insurance (P = .35) and in patients younger than 65 (P = .07). Overall awareness of CT colonography decreased from 20.5% to 15.9% (OR 0.93, 95% CI 0.91-0.95). Reported optical colonoscopy utilization increased from 57.9% to 63.6% (OR 1.03, 95% CI 1.02-1.05).

CONCLUSION

Despite increasing self-reported utilization of optical colonoscopy from 2010 to 2015, survey results suggest that CT colonography awareness (∼16%) and utilization (∼1%) remain low. Improved public awareness and coverage expansion to Medicare-aged populations will promote improved CT colonography utilization and overall colorectal cancer screening rates.

Volumetric Textural Analysis of Colorectal Masses at CT Colonography: Differentiating Benign versus Malignant Pathology and Comparison with Human Reader Performance

RATIONALE AND OBJECTIVES

To (1) apply a quantitative volumetric textural analysis (VTA) to colorectal masses at CT colonography (CTC) for the differentiation of malignant and benign lesions and to (2) compare VTA with human performance.

MATERIALS AND METHODS

A validated, quantitative VTA method was applied to 63 pathologically proven colorectal masses (mean size, 4.2 cm; range, 3-8 cm) at noncontrast CTC in 59 adults (mean age, 66.5 years; range, 45.9-91.6 years). Fifty-one percent (32/63) of the masses were invasive adenocarcinoma, and the remaining 49% (31/63) were large benign adenomas. Three readers with CTC experience independently assessed the likelihood of malignancy using a 5-point scale (1 = definitely benign, 2 = probably benign, 3 = indeterminate, 4 = probably malignant, 5 = definitely malignant). Areas under the curve (AUCs) and accuracy levels were compared.

RESULTS

VTA achieved optimal sensitivity of 83.6% vs 91.7% for human readers (P = .034), with specificities of 87.5% and 77.4%, respectively (P = .007). No significant difference in overall accuracy was seen between VTA and human readers (85.5% vs 84.7%, P = .753). The AUC for differentiating benign and malignant lesions was 0.936 for VTA and 0.917 for human readers. Intraclass correlation coefficient among the human readers was 0.76, indicating good to excellent agreement.

CONCLUSION

VTA demonstrates excellent performance for distinguishing benign from malignant colorectal masses (≥3 cm) at CTC, comparable yet potentially complementary to experienced human performance.

Deep Learning Electronic Cleansing for Single- and Dual-Energy CT Colonography

Electronic cleansing (EC) is used for computational removal of residual feces and fluid tagged with an orally administered contrast agent on CT colonographic images to improve the visibility of polyps during virtual endoscopic "fly-through" reading. A recent trend in CT colonography is to perform a low-dose CT scanning protocol with the patient having undergone reduced- or noncathartic bowel preparation. Although several EC schemes exist, they have been developed for use with cathartic bowel preparation and high-radiation-dose CT, and thus, at a low dose with noncathartic bowel preparation, they tend to generate cleansing artifacts that distract and mislead readers. Deep learning can be used for improvement of the image quality with EC at CT colonography. Deep learning EC can produce substantially fewer cleansing artifacts at dual-energy than at single-energy CT colonography, because the dual-energy information can be used to identify relevant material in the colon more precisely than is possible with the single x-ray attenuation value. Because the number of annotated training images is limited at CT colonography, transfer learning can be used for appropriate training of deep learning algorithms. The purposes of this article are to review the causes of cleansing artifacts that distract and mislead readers in conventional EC schemes, to describe the applications of deep learning and dual-energy CT colonography to EC of the colon, and to demonstrate the improvements in image quality with EC and deep learning at single-energy and dual-energy CT colonography with noncathartic bowel preparation. ©RSNA, 2018.

Computed Tomography Colonography Less Costly Than Colonoscopy for Colorectal Cancer Screening of Commercially Insured Patients

BACKGROUND

Computed tomography (CT) colonography's effectiveness, its associated patient advantages, and its potential role to increase colorectal cancer (CRC) screening rates have been demonstrated in previous research, but whether CT colonography has a cost advantage relative to optical colonoscopy for the commercially insured US population has not been assessed.

OBJECTIVE

To compare the costs of CRC screening using CT colonography or optical colonoscopy for commercially insured people in the United States.

METHODS

Using retrospective commercial healthcare claims data and peer-reviewed studies, we performed a simulated multiyear, matched-case comparison of the costs of CT and optical colonoscopies for CRC screening. We estimated commercial optical colonoscopy costs per screening based on the 2016 Truven Health MarketScan Commercial Database and ancillary services, such as bowel preparation, anesthesia, pathology, and complication costs. We developed 4 scenarios for CT colonography cost per screening using the ratio of commercial to Medicare fees, and calculated ancillary service and follow-up costs from payers' costs for these services when associated with optical colonoscopies. For comparison, we converted the costs per screening to the costs per screening year per person using real-world screening intervals that were obtained from peer-reviewed studies.

RESULTS

In 2016, the average optical colonoscopy screening cost for commercial payers was $2033 (N = 406,068), or $340 per screening year per person. With our highest-cost CT colonography scenario, CT colonography costs 22% less, or $265 per screening year, than optical colonoscopy, mostly because of the advantages for patients of no anesthesia and the greatly reduced use of pathology services.

CONCLUSIONS

The use of CT colonography for CRC testing offers effective screening, patient-centered advantages, and lower costs compared with optical colonoscopy, and may be particularly appealing to the currently unscreened population with commercial health insurance. If the availability of CT colonography expands to meet the increased demand for it, CT colonography could cost up to 50% less than optical colonoscopy per screening year.

Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society

In the United States, colorectal cancer (CRC) is the fourth most common cancer diagnosed among adults and the second leading cause of death from cancer. For this guideline update, the American Cancer Society (ACS) used an existing systematic evidence review of the CRC screening literature and microsimulation modeling analyses, including a new evaluation of the age to begin screening by race and sex and additional modeling that incorporates changes in US CRC incidence. Screening with any one of multiple options is associated with a significant reduction in CRC incidence through the detection and removal of adenomatous polyps and other precancerous lesions and with a reduction in mortality through incidence reduction and early detection of CRC. Results from modeling analyses identified efficient and model-recommendable strategies that started screening at age 45 years. The ACS Guideline Development Group applied the Grades of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria in developing and rating the recommendations. The ACS recommends that adults aged 45 years and older with an average risk of CRC undergo regular screening with either a high-sensitivity stool-based test or a structural (visual) examination, depending on patient preference and test availability. As a part of the screening process, all positive results on noncolonoscopy screening tests should be followed up with timely colonoscopy. The recommendation to begin screening at age 45 years is a qualified recommendation. The recommendation for regular screening in adults aged 50 years and older is a strong recommendation. The ACS recommends (qualified recommendations) that: 1) average-risk adults in good health with a life expectancy of more than 10 years continue CRC screening through the age of 75 years; 2) clinicians individualize CRC screening decisions for individuals aged 76 through 85 years based on patient preferences, life expectancy, health status, and prior screening history; and 3) clinicians discourage individuals older than 85 years from continuing CRC screening. The options for CRC screening are: fecal immunochemical test annually; high-sensitivity, guaiac-based fecal occult blood test annually; multitarget stool DNA test every 3 years; colonoscopy every 10 years; computed tomography colonography every 5 years; and flexible sigmoidoscopy every 5 years. CA Cancer J Clin 2018;68:250-281. © 2018 American Cancer Society.

Detection of potentially relevant extracolonic and colorectal findings at CT colonography in a low-risk symptomatic patient population

PURPOSE

CT colonography (CTC) is a widely accepted examination tool for detection of colorectal lesions but evidence of the proportions of relevant extracolonic findings (ECF) in a large symptomatic but still relatively low-risk cohort is lacking, as well as their relationship to symptoms, age, and sex.

METHODS

All patients (n = 3208) with colorectal symptoms, imaged between January 2007 and September 2016 with first-time CTC, were retrospectively selected. The majority (96.7%) was examined with low-dose unenhanced protocol. The most relevant ECF and colorectal lesions (≥6 mm) were prospectively assessed according to C-RADS classifications. Follow-up was elaborated based on the electronic record review. Chi-square test was utilized for evaluating the associations between relevant findings and symptoms, age, and sex.

RESULTS

A total of 270 (8.4%) patients were classified as C-RADS E3, 63 (2.0%) patients as C-RADS E4, and 437 (13.6%) patients were assessed with colorectal lesions (C-RADS C2-4). At follow-up, two thirds of ECF turned out to be a malignancy or relevant disease that required further medical attention. The proportion of ECF was not related to specific colorectal symptoms. Patients aged ≥65 years and men had significantly higher proportions of ECF than younger patients (C-RADS E3 p = 0.005; C-RADS E4 p < 0.001) and women (C-RADS E3 p = 0.013; C-RADS E4 p = 0.009), respectively.

CONCLUSION

Proportions of relevant ECF and colorectal findings are relatively low in symptomatic low-risk patients. By use of CTC as a singular examination, especially in elderly patients, most colonoscopies can be avoided with the benefit of diagnosing relevant ECF without introducing substantial over-diagnosis.

Radiographic capsule-based system for non-cathartic colorectal cancer screening

Many patients are reluctant to undergo optical colonoscopy for colorectal cancer screening. The Check-Cap colon imaging system is a non-invasive test that comprises an ingestible imaging capsule that emits and detects ultra-low-dose radiation. The capsule generates a 3D reconstruction of the colonic lumen for detection of polyps and cancer. Preliminary preclinical and clinical testing has demonstrated safety and feasibility. Mean radiation dose is estimated at 0.04 mSv. In conclusion, we describe a novel capsule-based, patient-friendly colorectal test that holds potential for non-invasive screening.

Predictors of primary care provider adoption of CT colonography for colorectal cancer screening

PURPOSE

To examine factors influencing primary care provider (PCP) adoption of CT colonography (CTC) for colorectal cancer (CRC) screening.

MATERIALS AND METHODS

We performed a retrospective cohort study linking electronic health record (EHR) data with PCP survey data. Patients were eligible for inclusion if they were not up-to-date with CRC screening and if they had CTC insurance coverage in the year prior to survey administration. PCPs were included if they had at least one eligible patient in their panel and completed the survey (final sample N = 95 PCPs; N = 6245 patients). Survey data included perceptions of CRC screening by any method, as well as CTC specifically. Multivariate logistic regression estimated odds ratios and 95% confidence intervals for PCP and clinic predictors of CRC screening by any method and screening with CTC.

RESULTS

Substantial variation in CTC use was seen among PCPs and clinics (range 0-16% of CRC screening). Predictors of higher CTC use were PCP perceptions that CTC is effective in reducing CRC mortality, higher number of perceived advantages to screening with CTC, and Internal Medicine specialty. Factors not associated with CTC use were PCP perceptions of less organizational capacity to meet demand for colonoscopy, number of perceived disadvantages to screening with CTC, PCP age and gender, and clinic factors.

CONCLUSION

Significant variation in PCP adoption of CTC exists. PCP perceptions of CTC and specialty practice were related to CTC adoption. Strategies to increase PCP adoption of CTC for CRC screening should include emphasis on the effectiveness and advantages of CTC.

Medicare cost of colorectal cancer screening: CT colonography vs. optical colonoscopy

PURPOSE

To compare the Medicare population cost of colorectal cancer (CRC) screening of average risk individuals by CT colonography (CTC) vs. optical colonoscopy (OC).

METHODS

The authors used Medicare claims data, fee schedules, established protocols, and other sources to estimate CTC and OC per-screen costs, including the costs of OC referrals for a subset of CTC patients. They then modeled and compared the Medicare costs of patients who complied with CTC and OC screening recommendations and tested alternative scenarios.

RESULTS

CTC is 29% less expensive than OC for the Medicare population in the base scenario. Although the CTC cost advantage is increased or reduced under alternative scenarios, it is always positive.

CONCLUSION

CTC is a cost-effective CRC screening option for the Medicare population and will likely reduce Medicare expenditures for CRC screening.

Colorectal Findings at Repeat CT Colonography Screening after Initial CT Colonography Screening Negative for Polyps Larger than 5 mm

Purpose To determine the rate and types of polyps detected at repeat computed tomographic (CT) colonography screening after initial negative findings at CT colonography screening. Materials and Methods Among 5640 negative CT colonography screenings (no polyps ≥ 6 mm) performed before 2010 at one medical center, 1429 (25.3%; mean age, 61.4 years; 736 women, 693 men) patients have returned for repeat CT colonography screening (mean interval, 5.7 years ± 0.9; range, 4.5-10.7 years). Positive rates and histologic findings of initial and repeat screening were compared in this HIPAA-compliant, institutional review board-approved study. For all patients with positive findings at repeat CT colonography, the findings were directly compared against the initial CT colonography findings. Fisher exact, Pearson χ², and Student t tests were applied as indicated. Results Repeat CT colonography screening was positive for lesions 6 mm or larger in 173 (12.1%) adults (compared with 14.3% at initial CT colonography screening, P = .29). In the 173 patients, 29.5% (61 of 207) of nondiminutive polyps could be identified as diminutive at the initial CT colonography and 12.6% (26 of 207) were missed. Large polyps, advanced neoplasia (advanced adenomas and cancer), and invasive cancer were seen in 3.8% (55 of 1429), 2.8% (40 of 1429), and 0.14% (two of 1429), respectively, at follow-up, compared with 5.2% (P = .02), 3.2% (P = .52), and 0.45% (P = .17), respectively, at initial screening. Of 42 advanced lesions in 40 follow-up screenings, 33 (78.6%) were right sided and 22 (52.4%) were flat, compared with 45.4% (P < .001) and 11.3% (P < .001), respectively, at initial screening. Large right-sided serrated lesions were confirmed in 20 individuals (1.4%), compared with 0.5% (P < .001) confirmed at initial screening. Conclusion Positive rates for large polyps at repeat CT colonography screening (3.7%) were lower compared with those at initial screening (5.2%). However, more advanced right-sided lesions were detected at follow-up CT colonography, many of which were flat, serrated lesions. The cumulative findings support both the nonreporting of diminutive lesions and a 5-10-year screening interval. ^© RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on August 30, 2016.

Emerging stool-based and blood-based non-invasive DNA tests for colorectal cancer screening: the importance of cancer prevention in addition to cancer detection

Colorectal cancer (CRC) screening can be undertaken utilizing a variety of distinct approaches, which provides both opportunities and confusion. Traditionally, there has often been a trade-off between the degree of invasiveness of a screening test and its ability to prevent cancer, with fecal occult blood testing (FOBT) and optical colonoscopy (OC) at each end of the spectrum. CT colonography (CTC), although currently underutilized for CRC screening, represents an exception since it is only minimally invasive, yet provides accurate evaluation for advanced adenomas. More recently, the FDA approved a multi-target stool DNA test (Cologuard) and a blood-based test (Epi proColon) for average-risk CRC screening. This commentary will provide an overview of these two new non-invasive tests, including the clinical indications, mechanism of action, and diagnostic performance. Relevance to radiology practice, including a comparison with CTC, will also be discussed.

Opportunistic Osteoporosis Screening: Addition of Quantitative CT Bone Mineral Density Evaluation to CT Colonography

PURPOSE

For patients undergoing CT colonography (CTC), the screening presents an opportunity for concurrent osteoporosis screening, without increasing radiation exposure or the time involved for the patient, using proximal femur quantitative CT-CT x-ray absorptiometry (QCT-CTXA).

METHODS

This cohort included 129 women and 112 men (mean age: 60.1 ± 8.2 years; range: 50-95 years) who underwent CTC between March 2013 and September 2014. Areal bone mineral density (BMD; g/cm(2)), and resultant left femoral neck T-score, was prospectively measured on the supine CT series. QCT results were reported with the CTC. Chart review evaluated whether the patients were eligible for BMD screening according to guidelines from the US Preventive Services Task Force and the National Osteoporosis Foundation guidelines; whether they had undergone prior BMD testing; and whether QCT results changed patient management.

RESULTS

Overall, 68.0% (164 of 241) of patients from this cohort had not previously undergone BMD screening. According to the National Osteoporosis Foundation guidelines, 44.0% (106 of 241) of patients were eligible for screening. T-scores within the osteopenic and osteoporotic range were detected in 32.3% (78 of 241) and 5.0% (12 of 241) of patients, respectively. Of these patients with low BMD, 66.7% (60 of 90) either had not previously undergone screening or were eligible for BMD testing. Reporting of QCT-CTXA T-scores altered management in 9 patients (3.7%) who had low BMD.

CONCLUSIONS

Maximizing the pre-existing value from imaging studies is crucial in the current era of health care reform. We demonstrate that colorectal and osteoporosis screening can be combined at CT examination, adding clinical and likely economic value.

Estimation of Benefits, Burden, and Harms of Colorectal Cancer Screening Strategies: Modeling Study for the US Preventive Services Task Force

IMPORTANCE

The US Preventive Services Task Force (USPSTF) is updating its 2008 colorectal cancer (CRC) screening recommendations.

OBJECTIVE

To inform the USPSTF by modeling the benefits, burden, and harms of CRC screening strategies; estimating the optimal ages to begin and end screening; and identifying a set of model-recommendable strategies that provide similar life-years gained (LYG) and a comparable balance between LYG and screening burden.

DESIGN, SETTING, AND PARTICIPANTS

Comparative modeling with 3 microsimulation models of a hypothetical cohort of previously unscreened US 40-year-olds with no prior CRC diagnosis.

EXPOSURES

Screening with sensitive guaiac-based fecal occult blood testing, fecal immunochemical testing (FIT), multitarget stool DNA testing, flexible sigmoidoscopy with or without stool testing, computed tomographic colonography (CTC), or colonoscopy starting at age 45, 50, or 55 years and ending at age 75, 80, or 85 years. Screening intervals varied by modality. Full adherence for all strategies was assumed.

MAIN OUTCOMES AND MEASURES

Life-years gained compared with no screening (benefit), lifetime number of colonoscopies required (burden), lifetime number of colonoscopy complications (harms), and ratios of incremental burden and benefit (efficiency ratios) per 1000 40-year-olds.

RESULTS

The screening strategies provided LYG in the range of 152 to 313 per 1000 40-year-olds. Lifetime colonoscopy burden per 1000 persons ranged from fewer than 900 (FIT every 3 years from ages 55-75 years) to more than 7500 (colonoscopy screening every 5 years from ages 45-85 years). Harm from screening was at most 23 complications per 1000 persons screened. Strategies with screening beginning at age 50 years generally provided more LYG as well as more additional LYG per additional colonoscopy than strategies with screening beginning at age 55 years. There were limited empirical data to support a start age of 45 years. For persons adequately screened up to age 75 years, additional screening yielded small increases in LYG relative to the increase in colonoscopy burden. With screening from ages 50 to 75 years, 4 strategies yielded a comparable balance of screening burden and similar LYG (median LYG per 1000 across the models): colonoscopy every 10 years (270 LYG); sigmoidoscopy every 10 years with annual FIT (256 LYG); CTC every 5 years (248 LYG); and annual FIT (244 LYG).

CONCLUSIONS AND RELEVANCE

In this microsimulation modeling study of a previously unscreened population undergoing CRC screening that assumed 100% adherence, the strategies of colonoscopy every 10 years, annual FIT, sigmoidoscopy every 10 years with annual FIT, and CTC every 5 years performed from ages 50 through 75 years provided similar LYG and a comparable balance of benefit and screening burden.

Sub-milliSievert ultralow-dose CT colonography with iterative model reconstruction technique

Purpose. The purpose of this study was to evaluate the technical and diagnostic performance of sub-milliSievert ultralow-dose (ULD) CT colonograpy (CTC) in the detection of colonic and extracolonic lesions.

Materials and Methods. CTC with standard dose (SD) and ULD acquisitions of 64 matched patients, half of them with colonic findings, were reconstructed with filtered back projection (FBP), hybrid (HIR) and iterative model reconstruction techniques (IMR). Image noise in six colonic segments, in the left psoas muscle and aorta were measured. Image quality of the left adrenal gland and of the colon in the endoscopic and 2D view was rated on a five point Likert scale by two observers, who also completed the reading of CTC for colonic and extracolonic findings.

Results. The mean radiation dose estimate was 4.1 ± 1.4 mSv for SD and 0.86 ± 0.17 mSv for ULD for both positions (p < 0.0001). In ULD-IMR, SD-IMR and SD-HIR, the endoluminal noise was decreased in all colonic segments compared to SD-FBP (p < 0.001). There were 27 small (6–9 mm) and 17 large (≥10 mm) colonic lesions that were classified as sessile polyps (n = 38), flat lesions (n = 3), or as a mass (n = 3). Per patient sensitivity and specificity were 0.82 and 0.93 for ULD-FBP, 0.97 and 0.97 for ULD-HIR, 0.97 and 1.0 for ULD-IMR. Per polyp sensitivity was 0.84 for ULD-FBP, 0.98 for ULD-HIR, 0.98 for ULD-IMR. Significantly less extracolonic findings were detected in ULD-FBP and ULD-HIR, but in the E4 category by C-RADS (potentially important findings), the detection was similar.

Conclusion. Both HIR and IMR are suitable for sub-milliSievert ULD CTC without sacrificing diagnostic performance of the study.

Objective and Subjective Intrapatient Comparison of Iohexol Versus Diatrizoate for Bowel Preparation Quality at CT Colonography

OBJECTIVE

The purpose of this study is to objectively and subjectively compare nonionic iohexol and ionic diatrizoate iodinated oral contrast agents as part of a cathartic bowel regimen within the same CT colonography (CTC) cohort, with otherwise identical preparations.

MATERIALS AND METHODS

In this retrospective study, 46 adults with no symptoms (mean age, 59.4 years; 26 men and 20 women) returning for follow-up CTC over a 9-month interval underwent the same bowel preparation with the exception of 75 mL of iohexol 350 in place of 60 mL of diatrizoate. All other preparation components (bisacodyl, magnesium citrate, and 2% barium) remained constant. Objective volumetric analysis of residual colonic fluid volume and fluid attenuation was performed. Additionally, two radiologists experienced with CTC who were blinded to the specific bowel preparation scored each of six colonic segments for adherent residual solid stool using a previously validated 4-point scale (0 for no stool; 1-3 for increasing residual stool). A paired t test was used for comparison of the cohorts.

RESULTS

No clear clinically meaningful difference was found between the two preparations on overall objective or subjective evaluation. The mean (± SD) residual fluid volume was 173 ± 126 mL with the iohexol preparation and 130 ± 79 mL with the diatrizoate preparation (p = 0.02). The mean total colonic stool score was 2.5 (0.42/segment) with iohexol and 2.3 (0.38/segment) with diatrizoate (p = 0.69). The mean fluid attenuation was higher with iohexol (849 ± 270 HU) compared with diatrizoate (732 ± 168 HU) (p = 0.03).

CONCLUSION

On the basis of this direct intrapatient comparison, we found that oral iohexol is a suitable alternative to diatrizoate for fluid tagging as part of a cathartic bowel preparation at CTC. Because this nonionic tagging agent is more palatable, less expensive, and likely safer than ionic diatrizoate, our CTC program now uses iohexol as the standard recommended regimen.