Colon cancer is the second leading cause of cancer death in the United States, and it accounts for approxi mately 10% of all cancer deaths in both men and women combined [2, 3]. 150,000 new cases and 50,000 deaths result from colon cancer every year in the United States . This translates into 137 deaths per day or six deaths per hour. This is unfortunate, since most cases of colon cancer are preventable if detected as precancerous adenomas. It is estimated that up to 80-90% of all cases of colon cancer develop from small adenomas that undergo mutations and slowly advance over time .
However, it should be noted that most adenomas do not progress to colon cancer, and the vast majority of diminutive lesions (< 5 mm) in the colon are non-adenomas [5, 6]. This has led to debate in the medical community about the size at which a colon lesion should be considered clinically important . Most gastroenterologists feel that the small lesions are probably not important if routine screening is performed. Larger lesions (those over 5 mm) should be removed unless there are contraindications to endoscopy and polypectomy, or if the patient is of an advanced age. Unfortunately, some colon cancers develop very rapidly and would not be detected even with the current screening techniques.
A number of screening options are available for the detection of precursor adenomas in the colon. These include fecal occult blood test (FOBT), sigmoidoscopy, double contrast barium enema (DCBE), and colonoscopy [2, 8]. Both FOBT and sigmoidoscopy have been shown to decrease the morbidity and mortality of colon cancer [9, 10]. However, there is a growing consensus that a full structural examination of the colon is warranted in order to optimize colon cancer screening. This can be performed by DCBE, colonoscopy, or CTC.
Complete colonoscopy allows the most thorough evaluation of the colon with the added benefit of the possibility of biopsy or excision of suspicious lesions. Colonoscopy is considered the reference standard for colonic evaluation . However, there are several important limitations to the widespread use of screening colonoscopy, including need for sedation, the potential risk of perforation and bleeding (0.1-0.3%), costs of the procedure including the need for sedation, failure to complete the examination in 5-10% of patients, and an insuf ficient workforce of trained endoscopists to meet increased demand. Moreover, in an optimized study, the sensitivity of CTC was superior to colonoscopy for detecting adenomas over 10 mm . Other studies have also shown that CTC can detect larger lesions that were missed at colonoscopy . For these reasons, CTC is being further investigated and is being used clinically to evaluate the colon for polyps and cancers.
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