Medicine Section - In Vivo Analysis of Colorectal Polyps

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

During a colonoscopy or sigmoidoscopy as a screening test for colorectal cancer, the physician must often decide which polyp should be removed for histologic diagnosis. While hyperplastic polyps are considered benign without malignant potential, adenomatous polyps are thought to represent one of the earliest stages in the progression to a malignancy. Identification of these premalignant lesions is considered one of the cornerstones of colorectal cancer prevention. The physician must thus balance the time and potential morbidity of removing all polyps, many of which will be benign, versus removal of those polyps most likely to be adenomatous.

Recently a spectrophotometry technique has been developed as an adjunct to colonoscopy that is intended to distinguish between normal and precancerous tissue. This system is based on the observation that benign and malignant tissue emit different patterns and wavelengths of fluorescence after exposure to a laser light. One such device was approved by the Food and Drug Administration (FDA) in 2000, the Optical Biopsy System (SpectraScience, Minneapolis MN). This system consists of an optical fiber, emitting a laser that is directed against three different regions of the same polyp. The subsequent florescent signal is collected, measured, and analyzed by a proprietary software system, which classifies a polyp as "suspicious" (i.e., adenomatous) or "not suspicious" (i.e., hyperplastic).

Narrow band imaging (NBI) is another new technique that allows visualization of the mucosal surface and capillary vessels and thus may assist in the differentiation of abnormal from normal mucosa during colonoscopy. Two NBI systems are available. The NBI color chip system is used in the United States; in this system a single filter with a 2-band pass characteristic is used to generate central wavelengths at 415 nm (blue) and 540 nm (green and red). The NBI red-green-blue sequential illumination system uses narrow spectra of red, green, and blue light and a video endoscopic system with a frame sequential lighting method. The light source unit consists of a xenon lamp and a rotation disk with 3 optical filters. The rotation disk and monochrome charge-coupled device are synchronized and sequentially generate image in 3 optical filter bands. By use of all 3 band images, a single color endoscopic image is synthesized by the video processor. NBI has limited penetration into the mucosal surface and has enhanced visualization of capillary vessels and their fine structure on the surface layer of colonic tissue.

The FDA-labeled indication for the Optical Biopsy System reads as follows:

"The SpectraScience Optical Biopsy System is indicated for use as an adjunct to lower gastrointestinal endoscopy. The device is intended for the evaluation of polyps less than 1 cm in diameter that the physician has not already elected to remove. The device is only to be used in deciding whether such polyps should be removed (which includes submission for histological examination)."

NBI received FDA clearance through the 510K process in 2005. This clearance (K051645) added NBI with the EVIS EXERA 160A System (Olympus Medical Systems Corp) to existing endoscopic equipment. FDA indications are for endoscopic diagnosis, treatment, and video observation.

Policy/Criteria

Fiberoptic analysis of colorectal polyps is considered investigational.

Scientific Background

The FDA approval for the SpectraScience™ Optical Biopsy™ System was based on a prospective, non-randomized phase II study involving 101 subjects from 5 sites. The data from this trial have not been published in a peer-reviewed journal but are available as an FDA summary of safety and effectiveness. (1) Patients who participated in the study had undergone a prior lower GI endoscopic procedure with at least one polyp identified. They were then referred for an additional colonoscopy exam, in which fiberoptic analysis of the polyps was performed. At the time of the colonoscopy, the physicians documented whether or not the polyp was considered hyperplastic or adenomatous, and whether or not they would remove the polyp. The fiberoptic probe was then applied to three different portions of the polyp and a segment of normal adjacent mucosa. The physician did not know the results of the analysis and thus the test did not affect patient treatment. The effectiveness of the analysis was then calculated as its ability to correctly identify adenomatous polyps (sensitivity) and to correctly identify hyperplastic polyps (specificity), either alone or in conjunction with the physician assessment. The sensitivity and specificity of the physician assessment alone was 82.7% and 50%, respectively, compared to a combined sensitivity and specificity of 96.3% and 33%, respectively. In other words, fiberoptic analysis identified additional adenomatous polyps that the physician had classified as hyperplastic and presumably would not have removed based on visual assessment alone. This increase in sensitivity comes at the price of a decrease in specificity, as more hyperplastic polyps will undergo biopsy. However, according to the FDA, the risk of taking biopsies of additional hyperplastic polyps is minimal.

The clinical significance of these results and their effect on patient management is difficult to interpret from the data presented. It is not clear how the physician decided to select additional polyps for fiberoptic analysis (it is not entirely clear whether all polyps were analyzed and then underwent biopsy), or whether the same results could be obtained by simply randomly taking a biopsy of a subset of polyps that were considered hyperplastic on visual assessment. While adenomatous polyps are considered premalignant lesions, the evolution to cancer is a slow process requiring 7 to 8 years, and thus the immediate removal of all adenomatous polyps is not required. In addition, the finding of an adenomatous polyp serves as a marker that the patient should undergo more frequent endoscopic exams. It is well known that the current practice of visual inspection of polyps will certainly miss some adenomatous polyps, but this lack of sensitivity is considered acceptable if at least one adenomatous polyp is identified and the patient undergoes more frequent screening.

An updated search of the MEDLINE database identified no new studies addressing the above limitations.  One study identified in the published literature was a feasibility study of fiberoptic analysis of normal, adenomatous and cancerous tissue in 11 patients. (3)  A more recent study by Dhar and colleagues reported results of spectral scattering to differentiate colonic lesions in a small series of 45 patients. (4)  Studies are ongoing to evaluate a number of techniques for in vivo evaluation of colonic lesions; these techniques include magnifying endoscopy, chromoendoscopy, endocytoscopy, spectroscopy, and confocal microscopy.

Several studies from outside the United States were identified that used the narrow band imaging (NBI) system. (5,6) For example, Hirata evaluated 148 colorectal lesions and concluded that determination of pit patterns of colorectal neoplasia by NBI magnification was nearly the same as that by standard magnification with chromoendoscopy and that NBI can distinguish neoplastic and non-neoplastic lesions without chromoendoscopy. (5) However, these studies only reported on the accuracy of the NBI system in the in vivo evaluation of colonic polyps. None of the studies evaluated the impact of this technology on outcomes including whether or not there would be an improvement in the selection of polyps for removal during colonoscopy. In an editorial, Soetikno mentions the need for a user-friendly classification system for use of these devices. (7) The editorial also comments on the need for high-definition recording devices to allow further research. As noted, without these devices the details of lesions cannot be seen beyond the fleeting moment during the procedure and patterns cannot be fully correlated with pathology.

References

1. BlueCross Blue Shield Association Medical Policy Reference Manual Policy No. 2.01.51
2. Optical Biopsy System: Summary of Safety and Effectiveness. www.fda.gov/cdrh/pdf/p990050b.pdf   (Verified 7/20/07)
3. Mayinger B, Jordan M, Horner P et al. Endoscopic light-induced autofluorescence spectroscopy for the diagnosis of colorectal cancer and adenoma. J Photochem Photobiol B 2003;70(1):13-20
4. Dhar A, Johnson KS, Novelli MR et al. Elastic scattering spectroscopy for the diagnosis of colonic lesions: initial results of a novel optical biopsy technique. Gastrointest Endosc 2006;63(2):1257-61
5. Hirata M, Tanaka S, Oka S et al. Magnifying endoscopy with narrow band imaging for diagnosis of colorectal tumors. Gastrointest Endosc 2007; 65:988-95
6. Tischendorf JJ, Wasmuth HE Koch A et al. Value of magnifying chromoendoscopy and narrow band imaging (NBI) in classifying colorectal polyps: a prospective controlled study. Endoscopy 2007; 39:1092-6
7. Soetikno R, Kalenbach T. The beginning of a new paradigm in colonoscopy? Gastrointest Endosc 2007; 65:996-7

Cross References

None

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