Virtual Colonoscopy Using Omnipaque as a Contrast Agent

Study Overview
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Brief Summary
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CT colonography (CTC) is a validated screening exam for colorectal cancer. The diagnostic accuracy of CTC depends on the quality of the bowel cleansing and contrast tagging of residual stool and fluid. New bowel preparation media for CTC should be assessed for their efficacy and for patient satisfaction. Iohexol is currently approved by the FDA for oral use for imaging of the gastrointestinal tract. A potential advantage of using iohexol for CTC is that low-and iso-osmolar oral contrast agents have fewer risks than hyperosmolar contrast agents, which make them ideal for use in all patients, especially those who are frail and/or have multiple co-morbidities. For example, hyperosmolar contrast agents that are accidentally aspirated into the lungs during ingestion may result in life-threatening acute pulmonary edema and severe chemical pneumonitis, which is not the case for low- and iso-osmolar contrast agents. It may even be safer to use low- or iso-osmolar contrast agents for patients undergoing CTC on the same day as their incomplete colonoscopy, since they are at risk for aspiration from being sedated for their colonoscopy. Additionally, unlike hyperosmolar contrast agents, low- and iso-osmolar contrast agents do not cause sudden and massive fluid shifts, thus eliminating the risk of dangerous electrolyte imbalances.

Detailed Description
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Colorectal cancer is the third most common cancer and the second leading cause of cancer-related mortality in the United States when both sexes are combined. Given that the time interval between the appearance of a pre-malignant adenoma and its progression to invasive carcinoma is approximately 5.5 years for polyps >10 mm and 10-15 years for smaller polyps, colorectal cancer is an ideal disease for screening because there is sufficient time to detect and remove pre-malignant adenomas. However, even though screening has been shown to decrease colorectal cancer mortality, only about 60% of people over the age of 50 have had the recommended screening tests. First introduced in 1994, computed tomography colonography (CTC) is a validated colorectal cancer screening exam by the American Cancer Society. It is a low-radiation dose CT scan of the colon that is performed after bowel preparation and gas insufflation of the colon. CTC has several advantages over optical colonoscopy including less invasiveness, no need for sedation, improved patient comfort, and the ability to identify extracolonic findings. The performance of CTC for polyp detection compares favorably to that of optical colonoscopy and CTC is rapidly gaining acceptance as a screening and diagnostic technique. For accurate diagnosis in CTC, the colon must be adequately cleansed and any residual stool and fluid must be tagged so that they do not obscure polyps or masses. Patients often find bowel preparation to be the most onerous part of the screening process because it is inconvenient and uncomfortable. Many bowel preparations for CTC and optical colonoscopy require ingestion of large volumes of laxative solutions that can lead to nausea, abdominal pain and diarrhea. Additionally, for CTC, currently the most widely used tagging agents are hyperosmolar iodinated and barium based agents such as diatrizoate meglumine and diatrizoate sodium solution (Gastrografin; Bracco Diagnostics, Monroe Township, NJ), a hyperosmolar ionic iodinated contrast agent. These hyperosmolar agents can also lead to nausea, abdominal pain and diarrhea, and can even result in dangerous electrolyte balances from rapid fluid shifts. Changing the current bowel preparation regimen to improve patient comfort, convenience, and safety would most likely increase patient compliance with CTC. Iohexol (Omnipaque; GE Healthcare, Milwaukee, WI) is a low-osmolar non-ionic iodinated contrast agent that is approved by the FDA for oral use. It is routinely used orally for CT scans of the abdomen and pelvis, and has been used experimentally in CTC. Iohexol is better tolerated by patients and has a better safety profile than hyperosmolar iodinated and barium based contrast agents. Study Hypotheses Oral iohexol in conjunction with a minimally cathartic agent results in adequate bowel preparation for CTC. Oral iohexol provides effective tagging of residual stool and fluid in standard screening and diagnostic CTC and same-day CTC following incomplete optical colonoscopy. Oral iohexol is well tolerated by patients in terms of taste, ease of preparation, and side effects.

Official Title
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Low-osmolar Contrast Tagging in Minimal Cathartic CT Colonography

Conditions
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Colorectal Cancer

Intervention / Treatment
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* Drug: Iohexol


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age ≥18 years able to provide written informed consent Exclusion Criteria: hypersensitivity to iodine-containing compounds, pregnant or lactating, diuretic therapy, and enrollment in other clinical research trials involving investigational drugs

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| patients undergoing CTC receiving iohexol<br>Patients will be recruited from a pool scheduled to undergo screening or diagnostic CTC for clinical purposes. They will be given 50 ml of Iohexol as a oral contrast | Drug: Iohexol<br>* Iohexol (Omnipaque; GE Healthcare, Milwaukee, WI) is a low-osmolar non-ionic iodinated contrast agent that is approved by the FDA for oral use. It is routinely used orally for CT scans of the abdomen and pelvis, and has been used experimentally in CTC. Iohexol is better tolerated by patients and has a better safety profile than hyperosmolar iodinated and barium based contrast agents.<br>* Other names: OMNIPAQUE;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| adequate bowel preparation | Two experienced board-certified abdominal imaging radiologists trained in reading CTC will assess percent bowel preparation | Within 3 business days of completing CTC | 
| Amount of residual fluid and stool | Two experienced board-certified abdominal imaging radiologists trained in reading CTC will assess residual fluid in each of the six segments of the colon (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum)- Each segment will be scored as - 1 - none, 2 - <25%, 3 - 25-50%, 4: 50-75%, 5: >75% | Within 3 business days of completing CTC | 
| Efficacy of residual fluid and stool | Two experienced board-certified abdominal imaging radiologists trained in reading CTC will assess residual fluid in each of the six segments of the colon (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum)- Each segment will be scored as - 1 - none, 2 - <25%, 3 - 25-50%, 4: 50-75%, 5: >75% | Within 3 business days of completing CTC | 
| Amount of colonic bubbles | Two experienced board-certified abdominal imaging radiologists trained in reading CTC will assess residual fluid in each of the six segments of the colon (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum)- Each segment will be scored as - 1 - none, 2 - <25%, 3 - 25-50%, 4: 50-75%, 5: >75% | Within 3 business days of completing CTC | 
| Attenuation of tagged fluid | Two experienced board-certified abdominal imaging radiologists trained in reading CTC will assess residual fluid in each of the six segments of the colon (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum) It will be recorded in Hounsfield units from ROI of fluid in each segment | Within 3 business days of completing CTC | 
| Patient Satisfaction | Patient satisfaction with Omnipaque 350 as part of their bowel preparation regimen will be assessed with Likert scales in a questionnaire that patient will be asked to fill out after CTC. | immediately after CTC | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Assessing Workflow of incomplete colonoscopies | A subset analysis on the workflow of incomplete colonoscopies will also be performed. Specifically those patients who have an incomplete colonoscopy and have a CTC the same day with the Omnipaque regimen and those patients who choose to reattempt or forgo Colorectal cancer screening until a later date. The time and resources between those patients who have CTC on the same-day with the Omnipaque regimen after incomplete colonoscopy and the other subset will be compared and determination of the effectiveness of both workflows will be made. This will be used to gauge the productivity for the site. | through study completion, an average of 1 year | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Screening