Colon Cancer : Treating the Disease

by Food and Drug Administration (FDA)

(Page 3 of 4)

Meeting the Challenge

Virtual colonoscopy is one way science can provide more accurate and more comfortable screening. FDA first cleared this computer-assisted technology in 1995. As in the early devices, updated versions use digital information to produce a three-dimensional reconstruction of internal hollow structures of the human body, including the colon.

Before performing virtual colonoscopy, the bowel is first cleansed with oral laxatives. A small tube is inserted into the rectum and the colon is inflated with air. A computerized axial tomography (CAT or CT) scan or magnetic resonance imaging (MRI or MR) is then performed. The entire procedure takes less than five minutes, and since sedation is usually unnecessary, the patient can leave immediately after the scanning is completed.

In earlier versions of these devices, the technician loaded the CAT or MRI images into a computer, where special software reconstructed the digital data into 3-D images. Now, with later versions, the digital data transfer and reconstruction are automated in "real time." Medical professionals can now "fly" inside the images, identifying polyps, cancers or other structural abnormalities. Using a computer mouse or a joy-stick, the doctor controls the speed of the voyage, going forward and backward — even making a complete circle — at will. The technology is able to consistently identify polyps 10 millimeters in diameter — about the size of a blueberry — or larger. If an abnormality is found, the patient then undergoes a conventional colonoscopy so the polyp can be removed.

There are other potential benefits to this new technology. For example, it may reduce the number of conventional colonoscopies performed for diagnostic purposes, and increase the number performed therapeutically for the specific purpose of removing polyps. These procedures also can provide an electronic record that can be stored, transmitted to distant locations, and used for future analysis. As the technology becomes more sophisticated, a cleansing bowel preparation may no longer be necessary, making the test even more acceptable to patients.

FDA's Harvey says that although the agency has cleared this new technology as a general radiological tool, there is not yet a Medicare coverage policy for virtual colonoscopy. In addition, many insurance companies do not currently pay for the procedure because outcome data from large patient groups are not yet available. Currently, virtual colonoscopy is most often performed in clinical trials designed to establish whether this type of testing is an effective method for colorectal cancer screening.

Other technologies may be available within the next several years, such as more accurate stool testing. These tests could be conducted in a manner similar to the current fecal occult blood tests. However, instead of testing for microscopic blood, these tests could detect DNA mutations in the cells that have been sloughed off by polyps and cancers. This approach promises to be more sensitive and specific in detecting abnormalities, and could result in fewer false positive tests.

According to the Mayo Clinic's Ahlquist, the ability to detect polyps accurately through virtual colonoscopy and DNA testing can reduce the frequency of testing, and thereby reduce overall medical costs. "The transition from a flat [normal] colon lining to a polyp to a cancer takes seven to 10 years. That's a large window of opportunity. If a diagnostic tool has the potential to detect the polyps, it probably does not need to be applied more frequently than every five years."

Treating the Disease

The type and duration of colorectal cancer treatment depend upon the extent of the disease and when it is discovered. Treatments can include surgery, chemotherapy, radiation, or a combination of all three.

Surgery is the most commonly performed treatment for colorectal cancer. If the tumor is discovered before it has penetrated the bowel wall, removal of the cancer is usually all that is necessary for a complete cure. Specific surgical procedures may require the removal of a portion of the large bowel, which is reconstructed by sewing or stapling the two ends together. In part due to new surgical techniques and devices, a colostomy, where a portion of the colon is rerouted through the abdominal wall to the outside surface and a bag is worn to collect wastes, may not be necessary.

Small cancers localized to the rectum can be removed surgically, with radiation therapy follow up. For large cancers that have grown through the rectal wall, a technique called "mesorectal excision" can be performed. The procedure allows removal of all cancerous tissue, but avoids severing of nerves involved in sexual and urinary function. Large rectal tumors are often treated with chemotherapy and radiation before surgery.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.