CT Colonoscopy Is Ready for Prime Time

CT colonography (CTC), also known as virtual colonoscopy, is equally effective, less invasive, safer and faster than standard colonoscopy for colon cancer screening.  Yet, CT colonography is not widely used.  That is because the US Preventive Services Task Force (USPSTF) has not endorsed screening CT colonography, and the Centers for Medicare & Medicaid Services (CMS) will not reimburse for the procedure although it does reimburse for diagnostic CTC.

A recent issue of the Journal of the American College of Radiology included an article that I co-authored with Abraham H. Dachman, MD on the subject.  In the article we document that existing peer-reviewed data support upgrading the USPSTF status of CT colonography along with Medicare’s reimbursement for it.

There are a number of advantages of CT colonography over standard colonoscopy.  CT colonography is minimally invasive, making it an excellent alternative for patients who may not want to undergo standard colonoscopy.  There is no need for sedation, making it suitable for an outpatient setting.  Patients can return to normal activities immediately after a CTC.  It is a safe procedure, with a very low risk for perforation (about 10- 20 times lower than for standard colonoscopy).  For those and other reasons, the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology endorsed CT colonography as an acceptable method to screen the colon for polyps and masses back in 2008.

Opponents to full acceptance of CT colonography raise a number of points, though.  They argue that patients with polyps need to undergo standard colonoscopy for polyp biopsy or removal.  However, it is estimated that fewer than 15 percent of patients having screening CT colonography will require standard colonoscopy because of polyps.

Another argument against CT colonography is its lower sensitivity for small polyps and flat lesions. It should be noted that standard colonoscopy also has decreased detection ability for small and flat lesions. However, the chance of a small polyp harboring malignancy is extremely low.

Opponents note that CT colonography is able to evaluate structures in the entire abdomen, outside the colon, and a drawback is the economic impact of the supplementary cost of the further workup and treatment of incidentally found lesions.  In fact, the majority of findings outside the colon that are identified by CT colonography will not require further workup.  Furthermore, CT colonography has the potential to save lives by detecting life-threatening lesions in a preclinical stage.

Keep in mind that CT colonography is a low-radiation dose procedure and requires much lower dose than a routine CT scan.  Also, methods to further reduce CT radiation dose have become widely available, including at UCSF, and those methods are used in CT colonography.  Moreover, current CT colonography doses can now be used that are at or below the natural background radiation in the United States.

The USPSTF is currently evaluating colorectal cancer screening tests. CT colonography should be a reimbursed colorectal cancer screening tool so that it can be a real option for those who do not want to undergo standard colonoscopy. Colorectal cancer most often starts in a polyp, and that is the target lesion for screening. CTC is fast, safe and effective for screening for those polyps most likely to become malignant, and it can help to save lives.