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Medicare’s Proposed Decision on CT Colonography for Colon Cancer

The Centers for Medicare and Medicaid Services (CMS) issued a proposed decision for screening computed tomography (CT) colonography (CTC) for colon cancer on February 11, 2009.  The proposed decision states that there is insufficient evidence to support screening coverage at this time.  CMS is seeking comments on their determination. Colorectal cancer (CRC), including colon cancer, is one of the three most common cancers and a leading cause of cancer deaths in the United States.  Early detection and treatment have been shown to improve survival.  Since 1998, Medicare has covered several CRC screening tests such as fecal occult blood tests, flexible sigmoidoscopy, and optical colonoscopy for average risk individuals.  In fact, there has been a decline in the colon cancer incidence rate since 1998 which may be associated with increased use of colorectal cancer screening.  This is primarily due to the removal of precancerous adenomatous polyps. Between 2000 and 2005, the percentage of adults aged 50 years and older who reported having had colonoscopy increased from 20% to 39%, whereas the percentage reporting testing for fecal occult blood decreased from 17% to 12%. In recent years, computed tomographic (CT scan) colonography, also referred to as virtual colonoscopy, has been studied as a screening test.

In 1997, Congress gave the Secretary of Health and Human Services the authority to cover additional colon cancer screening tests. CMS used this authority in 2003 to provide coverage for the fecal immunoassay test. Since individuals undergoing screening are asymptomatic, this requires a consideration of different factors than when considering a test of individuals with symptoms.  CMS believes that to recommend a screening test, there must be conclusive evidence that screening can alter the natural history of disease in a significant proportion of those screened.

CMS initiated an analysis to evaluate the evidence on CT colonography and to determine if the evidence is sufficient for Medicare coverage.  This analysis does not address the use of CT colonography as a diagnostic test.

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History of Medicare Coverage for Colon Cancer Screening Tests

Medicare currently covers (1) annual FOBTs (fecal occult blood test), (2) flexible sigmoidoscopy every 4 years, (3) screening colonoscopy for persons at average risk for colorectal cancer every 10 years, or for persons at high risk for colorectal cancer every 2 years, (4) barium enema every 4 years as an alternative to flexible sigmoidoscopy or colonoscopy, and (5) other procedures the Secretary finds appropriate based on consultation with appropriate organizations. See 42 C.F.R. §410.37. In the Physician Fee Schedule Final Rule for 2003, CMS amended the FOBT screening regulation definition at 42 C.F.R. § 410.37 (a) (2) to provide coverage of either (1) a guaiac-based FOBT, or (2) other tests as determined by the Secretary through a national coverage determination. See 67 Fed. Reg. 79966, 80040 (Dec. 31, 2002). On November 4, 2003, CMS issued a final Decision Memorandum indicating that effective November 4, 2003, Medicare would cover a screening immunoassay FOBT on an annual basis as an alternative to the guaiac-based FOBT.

Medicare Benefit Categories – Part A or Part B

Medicare is a defined benefit program. An item or service must fall within a benefit category under Part A or Part B as a prerequisite to Medicare coverage. Congress has specifically authorized coverage of certain colorectal cancer screening tests under Part B of the Medicare program and has consistently made necessary conforming changes in order to ensure that payments are made.

FDA Status

CT imaging devices (both hardware and software) presenting fly-through imaging of the colon have been cleared for colon cancer screening. There are numerous articles and opinions in the literature indicating that optical colonoscopy and CT colonography are nearly equivalent in terms of effectiveness and several medical and health organizations have endorsed its use.

Methodological Principles

When making national coverage decisions concerning the scope of the CRC screening benefit under Medicare Part B, CMS evaluates clinical evidence to determine whether or not the evidence is of sufficient quality to support a finding that a test is appropriate for general screening in the Medicare population.

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A. Introduction

The evaluation of screening tests has been standardized and accepted, according to the following criteria:

i. Simplicity.  It is essential that the tests used should be easy to administer and should be capable of use by para-medical and other personnel.
ii. Acceptability. As screening is in most instances voluntary and a high rate of cooperation is necessary in an efficient screening programme, it is important that tests should be acceptable to the subjects.
iii. Accuracy. The test should give a true measurement of the attribute under investigation.
iv. Cost. The expense of screening should be considered in relation to the benefits resulting from the early detection of disease, i.e., the severity of the disease, the advantages of treatment at an early stage and the probability of cure.
v. Precision (sometimes called repeatability). The test should give consistent results in repeated trials.
vi. Sensitivity. This may be defined as the ability of the test to give a positive finding when the individual screened has the disease or abnormality under investigation.
vii. Specificity. This may be defined as the ability of the test to give a negative finding when the individual screened does not have the disease or abnormality under investigation.

Literature Search

CMS searched PubMed from January 2003 to October 2008.  6 original studies and 6 reviews were found.

B. Discussion of evidence reviewed

Whitlock EP, Lin JS, Liles E, Bell TL, Fu R. Screening for colorectal cancer: a targeted, updated systematic review for the U.S. Preventive Services Task Force. Ann Intern Med 2008;149:638-658.

Whitlock and colleagues reported the results of a systematic review of colorectal cancer screening tests. The authors noted that CT colonography was as sensitive as colonoscopy for large adenomas and colorectal cancer.   Uncertainties remain for smaller polyps and frequency of colonoscopy referral.  They concluded that computed tomographic colonography seems as likely as colonoscopy to detect lesions 10 mm or greater but may be less sensitive for smaller adenomas.
Zauber AG, Knudsen AM, Rutter CM, Lansdorp-Vogelaar I, Savarino JE, van Ballegooijen M, Kuntz KM. Cost-effectiveness of CT colonography to screen for colorectal cancer. Report to AHRQ from the Cancer Intervention and Surveillance Modeling Network (CISNET) for MISCAN, SimCRC, and CRC-SPIN Models.

Zauber and colleagues reported the results of a cost-effectiveness analysis performed using 3 established colorectal cancer screening models. They noted that screening for colon cancer with CT colonography every 5 years with referral of individuals with a 6 mm or larger lesion to colonoscopy provides a benefit in terms of life-years gained that is comparable to that of five-year flexible sigmoidoscopy with annual FOBT and slightly lower than colonoscopy screening every 10 years. The cost of CT colonography relative to the benefit derived and to the availability and costs of other CRC screening tests, would need to be in the range of $108 to $205 to be a cost-effective alternative to all other available screening modalities, and in the range of $179 to $237 to be cost-effective compared to colonoscopy screening with CMS payment of approximately $500 for colonoscopy without polypectomy and $650 for colonoscopy with polypectomy.

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Washington State Health Care Authority. CT colonography for colorectal cancer screening. 2008. Available at

The Washington State Health Technology Clinical Committee (HTCC), an independent committee of 11 health practitioners, determines how selected health technologies are covered by several state agencies, reviewed CT colonography and does not provide coverage.  In their assessment (prepared by the Institute for Clinical and Economic Review) they concluded CT colonography was nearly as or equally sensitive as optical colonoscopy for detection of lesions > 10 mm on a per patient basis.  It was somewhat less sensitive on a per patient basis for smaller lesions or for detecting individual lesions.  CT colonography is relatively safe and existing data suggest that CT colonography is acceptable to patients, although it is unclear whether implementation of CT colonography to the colorectal screening armamentarium would result in increased rates of colorectal screening and overall earlier detection of colorectal cancer in the general population.

Winawer SJ. Colorectal cancer screening. Best Practice & Research Clinical Gastroenterology 2007;21:1031–1048.

Analysis of studies using CTC for the detection of colorectal polyps and cancer showed high sensitivity (93%) and high specificity (97%) of this technique for polyps of 10 mm or larger. However, for large and medium sized polyps combined (six millimetres or larger) the average sensitivity decreased to 86% with a specificity of 86%. When polyps of all sizes were included, studies were too heterogeneous in sensitivity (range, 45%–97%) and specificity (range, 26%–97%). While sensitivity of CTC for cancer and large polyps is satisfactory, detection of polyps in the six to nine millimetre size range is not satisfactory. Another important drawback of CTC for screening patients at increased risk is that flat lesions are missed.  However, a major disadvantage of CTC for its use as a screening procedure is the repeated patient exposure to substantial doses of ionising radiation. Lately, multidetector or multislice CT technology shortens scan time and reduces radiation dose while preserving high spatial resolution.  Another disadvantage is that the examination requires a complete bowel preparation. If patients need colonoscopy, they must undergo a second bowel preparation.
Rosman AS, Korsten MA. Meta-analysis comparing CT colonography, air contrast barium enema, and colonoscopy. American Journal of Medicine 2007;120:203-210.

Rosman and Korsten reported the results of a meta-analysis of 30 studies  published from 1996-2005. The pooled per patient sensitivities of CT colonography were 74% (95% CI, 66%-81%) overall, 56% (95% CI, 42%-70%) for polyps < 6mm, 63% (95% CI, 52%-75%) for polyps 6-10mm, and 82% (95% CI, 76%-88%) for polyps > 10mm. The pooled per patient specificity of CT colonography was 77% (95% CI, 69%-86%) overall. The authors concluded that CT colonography has a reasonable sensitivity and specificity for detecting large polyps but was less accurate than endoscopic colonoscopy for smaller polyps. Thus, CT colonography may not be a reasonable alternative in situations in which a small polyp may be clinically relevant.
Mulhall BP, Veerappan GR, Jackson JL. Meta-analysis: computed tomographic colonography. Ann Intern Med 2005;142:635-650.

Mulhall and colleagues reported the results of a systematic review of 33 studies (6393 individuals) published from 1975 to 2005. The pooled per patient sensitivities of CT colonography were 70% (95% CI, 53%-87%) overall, 48% (95% CI, 25%-70%) for polyps < 6mm, 70% (95% CI, 55%-84%) for polyps 6-9mm, and 85% (95% CI, 79%-91%) for polyps > 9mm. The pooled per patient specificity of CT colonography was 86% (95% CI, 84%-88%) overall. The authors concluded that computed tomographic colonography is highly specific, but the range of reported sensitivities is wide.  This heterogeneity raises concerns about consistency of performance and about technical variability. These issues must be resolved before CT colonography can be advocated for generalized screening for colorectal cancer.

Johnson CD, Chen MH, Toledano AY, Heiken JP, Dachman A, Kuo MD, et al. Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med 2008;359:1207-1217.

Johnson and colleagues reported the results of a study of 2600 adults at 15 centers “to assess the accuracy of CT colonography in detecting histologically confirmed, large colorectal adenomas and cancers (10 mm in diameter), with optical colonoscopy (the current clinical standard for colorectal cancer screening) and histologic review used as the reference standard.” All participants were 50 years of age or older, did not have symptoms of major bowel diseases, and were scheduled for routine colonoscopy. The study was conducted at 15 clinical sites in the United States. Exclusion criteria includes melena, hematochezia, lower abdominal pain, inflammatory bowel disease, familial polyposis, colonoscopy in past 5 years, complications from prior colonoscopy, anemia and a positive fecal occult blood test. The primary endpoint was “detection by CT colonography of histologically confirmed large adenomas and adenocarcinomas (10 mm in diameter or larger) that had been detected by colonoscopy.”

CT colonography was performed using at least 16 row multidetector CT scanners with colonic carbon dioxide insufflation and one milligram of subcutaneous glucagons. Preparation included laxative purgation, fluid and stool tagging with oral contrast.

Of the 2600 participants, complete data were available for 2531 (97%). Of these, 89% were considered at average risk for colorectal cancer. Mean age was 58 years. Men comprised 48% of the 2531. In per-patient analysis, the authors reported sensitivity, specificity, positive predictive value and negative predictive value for at least one lesion 6mm of 0.78, 0.88, 0.40 and 0.98, respectively; and for at least one lesion 10 mm of 0.90, 0.86, 0.23, and 0.99, respectively. In per-polyp analysis, the authors reported sensitivity for lesions 5mm of 0.70 and for lesions 10mm of 0.84. The authors reported that “extracolonic findings were observed in 66% of the participants; however, only 16% were deemed to require either additional evaluation or urgent care.” They concluded: “In this study of asymptomatic adults, CT colonographic screening identified 90% of subjects with adenomas or cancers measuring 10 mm or more in diameter. These findings augment published data on the role of CT colonography in screening patients with an average risk of colorectal cancer.” Participants were recruited from individuals already scheduled for routine colonoscopy. Segmental unblinding was not used. Repeat colonoscopy was advised for individuals with polyps 10mm on CT scans but not seen on colonoscopy. Individuals with a history of polyps or cancer were not specifically excluded and comprised 1% (34/2531) of the study. There was no follow up for health outcomes, extracolonic findings or subsequent testing. Radiologists participating in the study had specific training and were required to detect 90% of polyps 10mm on image testing.

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Graser A, Stieber P, Nagel D, Schaefer C, Horst D, Becker Cr, et al. Comparison of CT colonography, colonoscopy, sigmoidoscopy, and fecal occult blood tests for the detection of advanced adenoma in an average risk population. Gut (Online) 2008;doi:10.1136/gut.2008.

Graser and colleagues presented the results of a comparative study of 311 asymptomatic average risk adults “to compare the performance characteristics of five different screening tests in parallel for the detection of advanced colonic neoplasia.” Participants were “over 50 years of age and free of symptoms of colonic diseases like melaenic stools, hematochezia, diarrhoea, relevant changes in stool frequency, or abdominal pain.” Exclusion criteria included history of inflammatory bowel disease, family history for colorectal cancer and severe heart or lung disease. CT colonography was performed using 64 channel multidetector scanners with bowel preparation, oral contrast and CO2 insufflation. Colonoscopy was performed after CT colonography with segmental unblinding.

Of the 311 adults enrolled, 4 were excluded due to incomplete colonoscopy or withdrawal from the study. Of the remaining 307, 221 adenomas were detected in 113 participants. Of the adenomas, 147 were 5mm; 41 were 6-9mm; and 33 were 10mm in size. Of the 46 advanced lesions, 7 were 5mm; 6 were 6-9mm; and 33 were 10mm in size. For CT colonography, per polyp sensitivity was 70.1% for all adenomas; 59.2% for adenomas < 6mm; 90.2% for 6-9mm; and 93.9% for > 9mm. For all adenomas, per person sensitivity was 84.1% and specificity was 47.4%. For adenomas > 5mm, per person sensitivity was 91.3% and specificity was 93.1%. For adenomas > 9mm, per person sensitivity was 92.0% and specificity was 97.9%.

On polyp size, the authors noted: “The relevance of diminutive and small polyps 1 – 9 mm in size has recently become a controversial topic. At least 20 – 30% of the average-risk asymptomatic population above age 50 carry adenomatous polyps. The majority of these are smaller than 10 mm. However, controversy exists as to the likelihood that small adenomas harbour significant advanced histology or progress to colorectal cancer. This has important implications on reporting and follow-up. A recent consensus proposal for CT colonography reporting suggested that diminutive polyps do not need to be reported and patients with 2 or less polyps <10 mm are recommended to undergo follow up CT colonography after 3 years rather than immediate colonoscopy for polypectomy, which is recommended for large polyps or if 3 or more small polyps are present. As small and medium size lesions may contain advanced histology, following this recommendation might lead to an increase in colorectal cancer incidence and mortality.”

The authors concluded: “High resolution and low dose CTC is feasible for colorectal cancer screening and reaches comparable sensitivities to colonoscopy for polyps >5 mm. For patients who refuse full bowel preparation and OC or CTC, FS should be preferred over stool tests. However, in case stool tests are performed, FIT should be recommended rather than FOBT.”

Cornett D, Barancin C, Roeder B, Reichelderfer M, Frick T, Gopal D, et al. Findings on optical colonoscopy after positive CT colonography exam. Am J Gastroenterol 2008;103:2068–2074.

Cornett and colleagues reported the results of a study “to evaluate the findings on optical colonoscopy (OC) in patients who had a positive screening CTC examination and to assess the number, size, shape, location, and pathology of polyps seen on OC but missed on CTC.” A total of 159 patients with polyps > 5mm seen on CT colonography underwent optical colonoscopy. Polyps 5mm were not reported by CT colonography per protocol. Mean age was 59.3 years. Men comprised 51% of the participants.

Of the 359 polyps detected on colonoscopy, 230 polyps were seen and reported on CT colonography (sensitivity = 64%). Of the 137 polyps seen on OC but not CT colonography, 99 (72%) were < 6mm, 27 (20%) were 6-9mm, and 11 (8%) were > 9mm in size. Of the 159 participants, 8 (5%) were considered false positives. The authors concluded: “CT colonography has adenoma miss rates similar to miss rates historically found with optical colonoscopy, with most missed adenomas being <10 mm and sessile in shape.” In this study, the results of the CT colonography were available to the colonoscopists prior to the optical colonoscopy.

Kim DH, Pickhardt PJ, Taylor AJ, Leung WK, Winter TC, Hinshaw JL, et al. CT Colonography versus colonoscopy for the detection of advanced neoplasia. N Engl J Med. 2007;357:1403-12.

Kim and colleagues reported the results of a study “to compare computed tomographic colonography (CTC) and optical colonoscopy (OC) when applied to the same general screening population.” Participants in a CT colonography screening program (n=3120) were compared to participants in a separate colonoscopy screening program (n=3163). Participants were referred by the same groups of primary care providers. Exclusion criteria included polyp surveillance, history of a bowel disorder, and hereditary nonpolyposis colorectal cancer syndrome. Main outcomes included detection of advanced neoplasia and total number of polyps removed. CT colonography was performed using 8 or 16 multidetector scanners with cathartic bowel preparation, oral contrast and carbon dioxide insufflation. Mean age was 57 years in the CT colonography group and 58 years in the colonoscopy group. Men comprised about 56% of both groups. Most participants did not have symptoms (about 98% in both groups) and did not have a family history of colorectal cancer (about 95% in the CT colonography group and 92% in the colonoscopy group).

Macari M, Bini EJ, Jacobs SL, Naik S, Lui YW, Milano A, et al. Colorectal polyps and cancers in asymptomatic average-risk patients: evaluation with CT colonography. Radiology 2004;230:629–636.

Macari and colleagues reported the findings of a case series of 69 men “to compare the results at thin-section multi–detector row CT colonography with those at conventional colonoscopy in the evaluation of colorectal polyps and cancer in a group of asymptomatic average-risk patients.” Participants were men older than 50 years who were scheduled to undergo screening colonoscopy and had no colorectal symptoms, prior polyps or family history of cancer. Main outcome was detection of colorectal polyps. Mean age was 55 years.

CT colonography was performed using a 4 detector CT scanner with bowel preparation and colonic insufflation. In per polyp analysis, the authors reported sensitivity of 60% (12/20) for polyps 6mm and 100% (3/3) for polyps 10mm. In per patient analysis, the authors reported specificity of 90% (26/29). The authors concluded: “In patients at average risk for colorectal cancer, CT colonography is a sensitive and specific screening test for detecting polyps 10 mm or larger; the sensitivity for detecting smaller polyps is decreased.” Adverse outcomes were not reported. Health outcomes were not reported.

Pickhardt PJ, Choi RJ, Hwang I, Butler JA, Puckett ML, Hildebrandt HA, et al. Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 2003;349:2191-200.

Pickhardt and colleagues reported the results of a study of 1233 asymptomatic adults at 3 centers “to evaluate the performance characteristics of virtual colonoscopy in a typical asymptomatic screening population.” Average risk individuals aged 50 to79 years and individuals with a family history of colorectal cancer aged 40 to 79 years were recruited through referrals for screening colonoscopy. Exclusion criteria included positive FOBT, anemia, rectal bleeding, history of polyps or cancer, and optical colonoscopy within previous 10 years. Main outcome was the detection of adenomatous polyps 6mm in diameter. CT scans were performed using 4 or 8 channel machines with colonic preparation, oral barium and colonic insufflation. Segmental unblinding was used. Mean age was 57.8 years. Men comprised 59% of the study population.

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For polyps 6mm, the authors reported per patient sensitivity and specificity of 88.7% and 79.6%, respectively. For polyps 10mm, the authors reported per patient sensitivity and specificity of 93.8% and 96%, respectively. The per polyp sensitivity was 85.7% for polyps 6mm and 92.2% 10mm. Total number of extracolonic findings was not reported but about 18% had findings that were considered of high or moderate clinical importance. There were “no clinically significant complications.” The authors noted that “at a threshold of 6 mm, 70.3 percent of the patients in our study would not have been sent for immediate polypectomy.” They concluded: “CT virtual colonoscopy with the use of a three-dimensional approach is an accurate screening method for the detection of colorectal neoplasia in asymptomatic average risk adults and compares favorably with optical colonoscopy in terms of the detection of clinically relevant lesions.

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