|Subject:||CT Colonography (Virtual Colonoscopy) as a Screening or Diagnostic Test for Colorectal Cancer|
|Policy #:||RAD.00029||Current Effective Date:||01/05/2016|
|Status:||Reviewed||Last Review Date:||11/05/2015|
This document addresses computed tomographic (CT) colonography (virtual colonoscopy) for both, screening and diagnosing colorectal cancer.
CT colonography, also known as virtual colonoscopy, is a diagnostic test that is intended to detect colorectal polyps and colorectal cancer. It involves the use of CT scanning and computer generated images to produce high resolution two and three-dimensional images of the colon and rectum. If suspicious lesions are detected, the individual must undergo further testing via a conventional colonoscopy.
Note: Radiation exposure should be taken into account when considering the use of this technology. Follow-up scanning should be limited to organ or area of interest.
For information on colonoscopy, please refer to CG-SURG-01 Colonoscopy.
Screening – Average Risk Individuals
CT colonography screening for colorectal cancer, beginning at age 50 (45 years for African Americans), at a frequency of every 5 years in the absence of an intervening colonoscopy, is considered medically necessary as an alternative to colonoscopy in individuals at average risk for colorectal cancer (i.e., those without specific risk factors or family history of colorectal cancer or adenomas and asymptomatic populations).
Screening – Higher Than Average Risk Individuals
CT colonography screening for colorectal cancer, beginning at an age appropriate for the specific high risk condition, at a frequency of every 5 years in the absence of an intervening colonoscopy, is considered medically necessary as an alternative to colonoscopy in individuals with a higher than average risk for colorectal cancer based on one or more of the following:
CT colonography for diagnosis of colorectal cancer is considered medically necessary as an alternative to colonoscopy in the following circumstances:
Investigational and Not Medically Necessary:
CT colonography is considered investigational and not medically necessary as a diagnostic test for colorectal cancer when:
Screening CT Colonography
Prior to 2008, the three largest studies addressing CT colonography (CTC) as a screening technique for colorectal cancer reported inconsistent findings. For example, two multi-institutional studies enrolling 1233 and 615 subjects, respectively (Pickhardt 2003, Cotton 2004) reported remarkably different sensitivities (94% vs. 55%) in detecting polyps greater than or equal to 10mm. A single institution study of 703 subjects reported high inter-observer variability (Johnson 2003). The reasons for these variable results were unclear, but were thought to be related to different CT protocols and experience of radiologists.
These initial studies were largely superseded by the American College of Radiology Imaging Network National (ACRIN) CT Colonography Trial (Johnson, 2008) that enrolled 2531 asymptomatic individuals at least 50 years of age from 15 research centers. Participants underwent standard bowel preparation, stool and fluid tagging, and mechanical insufflation prior to scanning with multidetector-row CT scanners. All CTC exams were interpreted by radiologists who had completed a specific training course. Colonoscopies and pathological examination of tissue specimens were performed the same day and used as the reference standard. Of the 2531 participants completing the trial, 2512 (99%) had same-day colonographic and colonoscopies available for comparison. CTC colonography identified 90% of polyps measuring 10 mm or more in diameter that were detected by optical colonoscopy. However, the colonography detection rate for smaller polyps (5 to 9 mm) ranged from 65% for 5 mm lesions to 90% for 9 mm lesions, with specificity ranging from 86–89%. The median size of lesions 5 mm in diameter that were detected and those that were missed on colonography was 10 mm and 6 mm, respectively. The study focused on lesions measuring 5 mm or more because the prevalence of advanced histologic features in polyps (less than 5 mm) is estimated to be below 2%. The study also identified extracolonic findings in 66% of the participants; however, only 16% were deemed to require either additional evaluation or urgent care. The authors concluded that CTC is an effective and less invasive option for colorectal cancer screening.
Results of the ACRIN study prompted the updated recommendations from the USPSTF, the American Cancer Society in association with other organizations and the American College of Gastroenterology. In 2008 The U.S. Preventive Services Task Force (USPSTF) updated its recommendation for colorectal cancer screening in average-risk adults age 50 years or older (Whitlock, 2008). With regards to the accuracy of CT colonography (CTC), the USPSTF concluded that as a screening test in the detection of colorectal polyps and neoplasia, CTC screening by trained and experienced radiologists yielded sensitivity similar to that of colonoscopy for colorectal cancer and large (≥10 mm) adenomas. However, it is not clear that CTC is as sensitive for smaller adenomas (≥6 mm) or what the proportion of false positive results will be.
The American Cancer Society, the US Multi Society Task Force on Colorectal Cancer, and the American College of Radiology released consensus recommendations for the screening and surveillance for the early detection of colorectal cancer and adenomatous polyps (Levin, 2008). The joint panel stated that recent data suggest CTC is comparable to optical colonoscopy for detecting cancer and polyps of significant size in average risk individuals "when state of the art techniques are applied". The panel concluded there are sufficient data to include CTC as an acceptable option for colorectal cancer screening. Screening intervals of 10 years are recommended for colonoscopy. However, since CTC has decreased sensitivity for small polyps compared to colonoscopy, a decreased screening interval is recommended. As noted by the guidelines:
The interval for repeat exams after a negative CTC has not been studied and is uncertain. However … it would be reasonable to repeat exams every 5 years if the initial CTC is negative for significant polyps until further studies are completed and are able to provide additional guidance.
The American College of Gastroenterologists (ACG) updated their guidelines on screening for colorectal cancer in 2008 (Rex 2009). These guidelines recognize that there are multiple options for colorectal cancer screening, including CTC, colonoscopy, flexible sigmoidoscopy, barium enema (BE) and fecal occult blood tests. The guidelines organize these options into "preferred screening recommendation" and "alternative colorectal cancer" prevention tests. Colonoscopy is designated the preferred recommendation, while CTC is considered an alternative test, particularly for those individuals unwilling to undergo colonoscopy. The guideline states that addition of CTC as a screening test was based on its performance in the ACRIN trial. Similar to the American Cancer Society Guidelines, the ACG recommends that screening with CTC should be performed at 5 year intervals.
The American College of Obstetricians and Gynecologists (ACOG) recommendations on Colonoscopy and Colorectal Cancer Screening Strategies (2011) includes CTC as an acceptable option for colorectal cancer screening for the detection of CRC and adenomas in average-risk women and men aged 50 years and older. The ACOG recommendations state that colorectal screening methods should be discussed with individuals to identify the methods they are most likely to accept and complete and acknowledges that "every screening method has advantages and limitations, which ultimately depends on the quality of the screening test, patient adherence and access to timely and appropriate follow-up."
The National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology® for colorectal cancer screening (V1.2015) stated the following with regards to CTC as a screening modality for colorectal cancer:
Currently there is not a consensus on the use of CT colonography (CTC) as a primary screening modality, and it is evolving with regards to recommended/programmatic frequency, polyp size leading to referral for colonoscopy, and protocol for evaluating extra colonic lesions. Also unclear is what follow-up is required for a patient with a positive CTC and negative colonoscopy… The current data available suggest that, if CTC is negative/no polyps, then repeat CTC in 5 y, and if positive/polyps lesions, colonoscopy should be performed.
All these organizations recognize that there are still gaps in knowledge regarding the use of CTC as a screening and diagnostic tool for the detection of CRC. Concerns have been raised regarding the frequency of CTC screening, potential morbidity related to repeated radiation exposure, the consequences of extracolonic findings, questions about test referral thresholds and whether the test performance seen in clinical studies will be reflected in CTC screening examinations in community settings. Some of these concerns are discussed in greater detail below.
Radiation exposure resulting from CTC is estimated to be 10 mSv per examination. The delayed effects of radiation exposure at this dose are not certain, but the National Research Council predicts that at this level of exposure, an additional 1 individual per 1000 would develop cancer (solid cancer or leukemia) in his or her lifetime. The cumulative (lifetime) radiation exposure risk from the use of screening CTC for colorectal cancer should be considered in the context of the cumulative radiation exposure from the use of other diagnostic and screening tests that involve radiation exposure. For example the American Cancer Society consensus guidelines recommend screening CTC be performed every 5 years in average-risk individuals in contrast to every 10 years for colonoscopy. A further issue discussed by this panel and in the published literature is the management of CTC detected polyps 6-9 mm in size and less than 3 in number (Kim 2007). While there remains some controversy over whether or not these can safely be followed with repeat CTC at intervals, widely accepted management recommendations have not been established. Until further evidence is available, the guideline recommends referral for colonoscopy for any individual with 6-9 mm polyps detected at CTC.
Computed tomographic colonography captures images of more than the colon. Extracolonic abnormalities that require further testing are found in as many as 16% of people having their first CTC. There is still insufficient evidence to assess the clinical consequences of identifying these abnormalities. Individuals may be emotionally and financially burdened when the additional diagnostic testing and procedures to further investigate the extracolonic lesions are found to have no clinical significance.
Recommendations on referring an individual for colonoscopy based on the size of a lesion found during CTC are largely based on expert opinion rather than clinical outcomes. Many experts currently suggest colonoscopy referral for a polyp 6 mm or greater. This results in colonoscopy referrals in as many as 1 in 3 persons, to as few as 1 in 8. Determining the appropriate polyp size for referral for colonoscopy after CTC examination is also influenced by the variability in polyp measurement between different readers, and varying approaches to CT measurement. Differences in the level of experience and the degree of training of radiologist readers has been cited as the major cause of discrepant test accuracy estimates for CTC in nonscreening populations.
Another issue is whether the accuracy of this test will be the same in the nonresearch setting as in clinical studies. Studies evaluating the accuracy of CTC have generally been carried out using an enhanced reference standard, which allows the separation of false-positive CTC results from false-negative colonoscopy results and reconciling differences with second look colonoscopy. Current studies have also been limited by using designs that compared a small number of experienced radiologists (2–15) to a larger number of experienced colonoscopists (5 to 50).
In summary, there is sufficient evidence to support the use of CT colonography as a screening tool for colorectal cancer for average-risk individuals, although there remain areas of controversy. Each individual and their healthcare practitioner should take into consideration the potential harms of CTC, including but not limited to the significant risk of radiation exposure, extracolonic findings and the possibility of the need to perform a colonoscopy based on the CT colonography findings.
Diagnostic CT Colonography
Regarding the diagnostic use of CTC, between 1.5% and 9% of individuals with colorectal cancer have synchronous cancers and for this reason several authors recommend the entire colon be assessed prior to surgery. This has been shown to influence the surgical procedure in some cases, and that total colon evaluation results in fewer recurrences, less distant metastases and longer disease free survival compared with those who do not undergo this assessment. In individuals with distal occlusive lesions, preoperative BE is technically difficult with an increased risk of barium inspissation, and may miss synchronous lesions in a third or more cases. Additionally up to 30% of synchronous cancers may be missed with intraoperative palpation. For individuals with distal obstructing lesions that prevent evaluation of the proximal colon by colonoscopy, CTC has been shown to be superior to BE in visualizing proximal colonic segments (97% vs. 60% in one study) and to correctly identify synchronous lesions (Fenlon, 1999).
Pickhardt and colleagues (2011) reported the findings of a systematic review and meta-analysis of published studies assessing the sensitivity of both CTC and optical colonoscopy (OC) for colorectal cancer detection. Diagnostic studies evaluating CT colonography detection of colorectal cancer were assessed utilizing predefined inclusion and exclusion criteria, in particular requiring both OC and histologic confirmation of disease. Studies that also included a means to assess true-positive versus false-negative diagnoses at OC (for example, segmental unblinding) were used to calculate OC sensitivity. The review did not provide an analysis of specific cancers since published studies generally report specificity for all lesions, including polyps, but not specifically for cancer. The review included 49 studies that provided data on 1151 individuals with a cumulative colorectal cancer prevalence of 3.6% (414 cancers). The review found the sensitivity of CTC for colorectal cancer was 96.1% (398 of 414; 95% CI: 93.8%, 97.7%). No heterogeneity was detected. The authors noted that no cancers were missed at CTC when both cathartic and tagging agents were used during bowel preparation. The sensitivity of OC for colorectal cancer, derived from a subset of 25 studies that included 9223 individuals, was 94.7% (178 of 188; 95% CI: 90.4%, 97.2%). A moderate degree of heterogeneity was present. The authors concluded that CTC is highly sensitive for colorectal cancer, especially when both cathartic and tagging agents are combined in the bowel preparation.
For routine diagnostic testing for colorectal cancer, there is limited evidence to support CTC as a first-line test over conventional studies that include BE and sigmoidoscopy. However, it would represent a reasonable approach in circumstances where diagnostic colonoscopy is indicated to rule out colorectal cancer but cannot be performed for technical or medical reasons, and BE and sigmoidoscopy, where feasible and appropriate, have been negative.
Description of Colon Cancer
According to the American Cancer Society, when men and women are considered separately, colorectal cancer is the third leading cause of cancer-related deaths in the United States and the second leading cause when both sexes are combined. Colorectal cancer is expected to cause about 50,830 deaths during 2013. Overall, the lifetime risk of developing colorectal cancer is approximately 1 in 20 (5%). This risk is slightly lower in women than in men (ACS, 2013).
Reductions in colorectal cancer morbidity and mortality can be achieved through detection and treatment of early-stage colorectal cancers and the identification and removal of adenomatous colon polyps, the precursors of colorectal cancer. Colorectal cancer screening tests have been shown to achieve accurate detection of early stage cancer and its precursors.
Description of CT Colonography (Virtual Colonoscopy)
Virtual colonoscopy involves the use of an imaging technique called computed tomography (CT) scanning to produce high resolution two- and three-dimensional images of the colon and rectum. The computer-generated images simulate the endoluminal view of the colon and rectum seen by conventional colonoscopy, which involves inserting a fiber optic camera into the colon for a visual inspection. Virtual colonoscopy requires the same bowel preparation steps as used for conventional colonoscopy; cessation of eating for a specific period prior to the procedure, ingestion of medicine to cleanse the bowel of fecal material, and introduction of air into the colon to expand it for better visualization. The rest of the procedure is very different from conventional colonoscopy. Instead of the physician administering medications to make the individual comfortable and inserting the colonoscope into the colon, the individual is asked to lie in a CT machine for about 20 minutes while the images are collected by computer. Following the CT procedure, a technician compiles the images collected to produce two and three dimensional representations of the colon for analysis by a physician.
Adenoma: A benign tumor that develops from or resembles glandular tissue.
Average Risk for Colorectal Cancer: Individuals without specific risk factors or family history of colorectal cancer or adenomas.
Colonoscopy: An endoscopic (fiberoptic) examination of the large intestine (colon).
Colorectal: Pertaining to or affecting the colon and rectum.
Neoplasia: A condition characterized by the abnormal and uncontrolled growth of cells.
Virtual colonoscopy: An examination of large intestine using computed tomography imaging technology.
The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.
When services may be Medically Necessary when criteria are met:
|74261||Computed tomographic (CT) colonography, diagnostic, including image postprocessing; without contrast material|
|74262||Computed tomographic (CT) colonography, diagnostic, including image postprocessing; with contrast material(s) including non-contrast images, if performed|
|74263||Computed tomographic (CT) colonography, screening, including image postprocessing|
When services are Investigational and Not Medically Necessary:
For the diagnostic procedure codes listed above when criteria are not met; or when the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.
Peer Reviewed Publications:
Government Agency, Medical Society, and Other Authoritative Publications:
|Websites for Additional Information|
Colorectal Cancer, Detection of
Colorectal Cancer, Screening
Colorectal Polyps, Screening Test
Three-Dimensional Computed Tomographic (CT) Colonography
|Medical Policy & Technology Assessment Committee (MPTAC) review. Updated review date, Rationale, Definitions, References and History sections of the document. Removed ICD-9 codes from Coding section.|
|MPTAC review. Updated review date, Rationale, References and History sections of the document.|
|MPTAC review. Updated review date, Background/Overview, References and History sections of the document.|
|MPTAC review. Updated review date, References and History sections of the document.|
|MPTAC review. Updated review date, Rationale, References and History sections of the document.|
|MPTAC review. Revised medically necessary criteria to clarify the age criteria related to screening average risk and higher than average risk individuals. Updated review date, References and History sections of the document.|
|MPTAC review. Medical necessity criteria revised to allow CT colonography for colorectal cancer screening as an alternative to colonoscopy in both average risk and higher than average risk individuals at a frequency of every 5 years in the absence of an intervening colonoscopy. Updated review date, rationale, definitions, references and history sections. Updated Coding section with 01/01/2010 CPT changes; removed codes 0066T and 0067T deleted 12/31/2009.|
|MPTAC review. Revised position statement to indicate CT colonography screening for colorectal cancer is considered medically necessary as an alternative to colonoscopy when the patient meets the medically necessary criteria for screening colonoscopy for individuals at average risk for colorectal cancer Updated review date, rationale, coding, references and history sections.|
|MPTAC review. Reviewed the American Cancer Society, the US Multi Society Task Force on Colorectal Cancer, and the American College of Radiology consensus guidelines for the detection of adenomatous polyps and colorectal cancer in asymptomatic average-risk adults (2008). No change to stance. Review date, rationale, references and history sections updated.|
|MPTAC review. Modified medically necessary criteria to clarify screening colonoscopy may be appropriate for average risk individuals who are unable to undergo colonoscopy for technical reasons. Modified language in third bullet of the position statement to clarify that the word "adenoma" refers to "colorectal adenoma". Modified investigational and not medically necessary criteria to clarify that CT colonography is not appropriate as a technique to screen for colorectal cancer in patients in whom colonoscopy is technically able to be performed sufficiently to visualize the colon. Other minor word changes made in the position statement section to provide clarity. Updated review date, rationale and history sections. The phrase "investigational/not medically necessary" was clarified to read "investigational and not medically necessary." This change was approved at the November 29, 2007 MPTAC meeting.|
|MPTAC review. Updated references and review date.|
|MPTAC review. Stance changed to include Medically Necessary and Investigational/Not Medically Necessary indications for diagnostic CT Colonography. Updated Rationale section and updated references.|
|Revised||12/01/2005||MPTAC review. Stance changed to include Medically Necessary indications. Updated Rationale section. Added information in the Discussion/General Information section and updated references.|
|11/17/2005||Added reference for Centers for Medicare and Medicaid Services (CMS) – National Coverage Determination (NCD).|
|Revised||07/14/2005||MPTAC review. Revision based on Pre-merger Anthem and Pre-merger WellPoint Harmonization.|
Last Review Date
|RAD.00029||Virtual Colonoscopy/CT Colonography as a Screening Test for Colorectal Cancer|
|WellPoint Health Networks, Inc.|
|4.06.03||CT Colonography (Virtual Colonoscopy) Screening for the Detection of Colorectal Polyps|