Preferred Screening Tests

Cancer prevention tests should be offered first. The preferred CRC prevention test is colonoscopy every 10 years, beginning at age 50. Screening should begin at age 45 years in African Americans. Cancer detection test should be offered to patients who decline colonoscopy or another cancer prevention test. The preferred cancer detection test is annual FIT for blood.

Alternative CRC Prevention Tests

Flexible sigmoidoscopy every 5 to 10 years. CT colonography every 5 years.

Alternative Cancer Detection Tests

Annual Hemoccult Sensa. Fecal DNA testing every 3 years.

Positive Family History but HNPCC Evaluation Not Indicated

Single first-degree relative with CRC or advanced adenoma diagnosed at age 60 years or older.

Recommended screening: Same as average risk. Single first-degree with CRC or advanced adenoma diagnosed before age 60 years, or two first-degree relatives with CRC or advanced adenomas:

Recommended screening: Colonoscopy every 5 years beginning at age 40 years or 10 years younger than age at diagnosis of the youngest affected relative

Familial Adenomatous Polyposis

Patients with classic FAP (>100 adenomas) should be advised to pursue genetic counseling and genetic testing, if they have siblings or children who could potentially benefit from this testing. Patients with known FAP or who are at risk of FAP based on family history (and genetic testing has not been performed) should undergo annual flexible sigmoidoscopy or colonoscopy, as appropriate, until colectomy is deemed by physician and patient to be the best treatment.

Patients with retained rectum after subtotal colectomy should undergo flexible sigmoidoscopy every 6 to 12 months. Patients with classic FAP, in whom genetic testing is negative, should undergo genetic testing for bi-allelic MYH mutations. Patients with 10 to 100 adenomas can be considered for genetic testing for attenuated FAP and if negative, MYH-associated polyposis.

Hereditary Nonpolyposis CRC

Patients who meet the Bethesda criteria should undergo microsatellite instability testing of their tumor or a family member's tumor, and/or tumor immunohistochemical staining for mismatch repair proteins.

Patients with positive tests can be offered genetic testing. Those with positive genetic testing, or those at risk when genetic testing is unsuccessful in an affected proband, should undergo colonoscopy every 2 years beginning at age 20 to 25 years, until age 40 years, then annually thereafter.

Modified from Rex DK, Johnson DA, Anderson JC, et al. American College of Gastroenterology guidelines for colorectal cancer screening 2008. Am J Gastroenterol 2009;104:739-750.

CT, Computed tomography, FAP, familial adenomatous polyposis; FIT, fecal immunochemical test; HNPCC, hereditary nonpolyposis colorectal cancer.

Colon Cancer And Scalp Lesions
Figure 38-32 "Apple core" lesion in colon cancer. (Courtesy Dr. PerryPernicano.)
Apple Core Lesion

Figure 38-33 Precancerous adenomas. (Courtesy Dr. Erik-Jan Wamsteker.)

do not have distal polyps. Although advocated as being more convenient than colonoscopy, because it is generally done in the office without the need for conscious sedation, only an estimated 30% of eligible patients undergo screening with flexible sigmoidoscopy (Nease et al., 2004). If polyps are identified during flexible sigmoidoscopy, a full colonoscopy is required to visualize the remaining colonic segments and to remove any remaining identified polyps.

Colonoscopy provides the most complete visualization of the entire colon and is the gold standard test for CRC screening. Since greater than half of all individuals who have advanced proximal adenomas may not have distal polyps, many investigators advocate the use of colonoscopy as the primary modality for CRC screening. The removal of pre-cancerous adenomas decreases CRC incidence by as much as 76% to 90% compared with no screening methodology (Figs. 38-33 and 38-34). One study using colonoscopy as a screening tool in U.S. military veterans discovered advanced villous adenomas in 10.5% of subjects (Fig. 38-35). Colo-noscopy carries a higher risk of adverse events attributed to therapeutic interventions such as biopsy and polyp removal, compared to FIT, DCBE, and flexible sigmoidoscopy, specifically bowel perforation and postpolypectomy hemorrhage.

Newer modalities for CRC screening are being developed. Virtual colonoscopy, or CT colonography, uses thin-section helical CT scans to generate high-resolution two-dimensional images that are reconstructed into three-dimensional images of the colon to evaluate for the presence of polyps. Direct comparison of CT colonography to colonoscopy in asymptomatic adults has shown sensitivity and specificity for polyp detection comparable to that of colonoscopy for polyps larger than 6 mm. CT colonography may be viewed as a more acceptable approach for CRC screening because it is less invasive and requires less time, without the potential adverse risks of sedation or bowel perforation. Most patients prefer conventional colonoscopy, reporting more pain, more

Figure 38-33 Precancerous adenomas. (Courtesy Dr. Erik-Jan Wamsteker.)

discomfort, and less respect from staff with CT colonography. As with conventional colonoscopy, CT colonography is limited by quality of the bowel preparation, procedural cost, lack of insurance coverage, variable physician training, and procedural time.

Capsule endoscopy is another emerging technology in the detection of CRC. The patient fasts overnight, ingests a disposable capsule, and begins water intake 2 hours after the capsule is ingested; the capsule is usually expelled within 48 hours of ingestion. The recorded information from the capsule is then downloaded and reviewed for abnormal

Cmv Colitis Endoscopy

pathology. Capsule endoscopy has become an accepted method for screening the small intestine for obscure GI bleeding. For colonic imaging, however, its use has been limited because of the larger colonic diameter, residual stool, and limited battery life of the capsule.

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