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Survival improves with diagnosis at an earlier stage. A reduction of 20% in the incidence of colorectal cancer in persons who are screened annually has been observed. Treatment of early-stage colorectal cancers may involve less invasive surgery and ultimately less adjuvant therapy.

Studies consistently show that fewer than 40% (and sometimes as low at 29%) of persons who should be screened for colorectal cancer have done so.

Everyone over age 50 should be screened for colon cancer. Persons with the following are considered to be at moderate risk and require more frequent screening:

• Personal history of adenomas and/or colorectal cancer
• Family history of adenomas and/or colorectal cancer
• Chronic inflammatory bowel disease

Effective screening tests have a high sensitivity (they are positive when a neoplasm, either an adenomatous polyp or cancer, is present) and a high specificity (they are negative when a neoplasm is absent).

Screening tests for colorectal cancer include:

• Fecal Occult Blood Testing (FOBT) - Screening for the presence of occult (hidden) blood in the stool is based on the fact that most cancers and some adenomatous polyps bleed (at least intermittently). FOBT is simple and noninvasive, but the test has poor sensitivity and can lead to unnecessary additional testing for follow up on false positive tests (because blood in the stool can come from other sources such as hemorrhoids). It has been found that up to 50 persons undergo colonoscopy for a positive FOBT for each case of colorectal cancer diagnosed. Current recommendations are that testing be conducted on two samples from three difference stool specimens on consecutive days. This increases the accuracy of the test in case any neoplasms that are present are bleeding only intermittently.

Two types of FOBTs are available: immunochemical FOBT and Guaiac FOBT. The Guaiac based FOBT has been shown to decrease the incidence of colorectal cancer by 20% and mortality by 33%. The Hemoccult II (Beckman Coulter, Inc.) is the most widely used Guaiac based FOBT in the United States. InSure (Enterix, Inc.) is the only immunochemical FOBT approved by the Food and Drug Administration in the United States. Cost of FOBT testing is approximately $5 for Guaiac based FOBT, and $30 for immunochemical FOBT.

Because of the potential to interfere with the test results, it is important to avoid aspirin and non-steroidal anti-inflammatory medications (e.g., Advil, Ibuprofen), foods high in vitamin C, and red meat for three days prior to the test.

• Flexible Sigmoidoscopy - This procedure provides direct visualization of the interior walls of the rectum and part of the colon using a flexible lighted tube and allows for the removal and biopsy of any suspicious lesions. One disadvantage is that it examines only that portion of the colon within reach of the instrument (approximately the distant third). Approximately 65-75% of adenomatous polyps and 40-65% of colorectal cancers are within reach of a 60cm flexible sigmoidoscope. Recommended frequency is every 5 years. The cost is approximately $150-300.

• Colonoscopy - This technique allows screening, diagnosis, and therapeutic management in one procedure. During this procedure, usually after light sedation, a thin lighted tube with a small camera attached is inserted into the rectum and samples of tissue may be collected for closer examination, or polyps may be removed. Colonoscopies can be used as screening tests or as follow-up diagnostic tools when the results of another screening test are positive. Colonoscopy can detect both polyps and cancers, although it is less accurate when the lesions are very small. The generally recommended interval for repeat colonoscopies for screening is every 10 years. Adverse events related to diagnostic colonoscopy include perforation and lower gastrointestinal bleeding and occur at a rate of approximately 12 per 10,000 colonoscopies. The cost is approximately $800-1600.