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Understanding current guidelines for colorectal cancer screening: A case-based approach

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Hereditary nonpolyposis colorectal cancer

Our patient’s family history meets the criteria for hereditary nonpolyposis colorectal cancer,23 ie, she has three family members with hereditary nonpolyposis colorectal cancer-associated cancers (colorectal cancer or cancer of the endometrium, small bowel, ureter, or renal pelvis), and one family member (her mother) is a first-degree relative of the other two affected relatives. Two successive generations of her family are affected, and one family member (her sister) was diagnosed before the age of 50.

People in families like this have an 80% lifetime risk of colorectal cancer, so it is imperative to review every patient’s family history. Patients who meet the criteria should be referred for genetic counseling and possibly genetic testing. In addition, they should begin screening—with colonoscopy, not the other tests—between the ages of 21 and 25 or at an age 10 years younger than when the youngest family member was diagnosed with colorectal cancer, whichever is earlier. They should subsequently undergo colonoscopy every 1 to 2 years.

These patients also have an increased risk of certain extracolonic cancers, including a 40% to 60% lifetime risk of endometrial adenocarcinoma. They and their physicians need to be aware of consensus screening recommendations for ovarian, endometrial, and transitional cell cancers.24

Familial adenomatous polyposis

Patients with familial adenomatous polyposis develop hundreds to thousands of adenoma-tous colorectal polyps, usually in their teens, and have a 100% risk of developing colon cancer if the colon is not removed. Patients with a family history of this disorder should undergo screening at 10 to 12 years of age.

OVERCOMING BARRIERS TO SCREENING

In 2004, an estimated 70.1 million Americans were 50 years of age and older and at average risk of colorectal cancer.25 Of these, only 28.3 million (40.4%) had undergone screening, and 41.8 million had not.

We could view this as an opportunity to make a significant impact on the disease, but resources are limited. Seeff et al25 estimated that it would take 10 years to perform screening colonoscopy on unscreened Americans if one-half of all current endoscopic capacity were used for screening alone.

Barriers to screening also exist on an individual level. A recent study26 found that only 50% of patients referred for screening colonoscopy actually underwent the procedure; patients were significantly less likely to make an appointment and keep it if they were younger or female or if they were on Medicaid. Reasons cited by patients for not following through with colonoscopy after referral included fear of pain or perforation, dislike of the bowel preparation, and misperceptions about colorectal cancer risk.

Understanding these barriers and improving patient-physician communication about the procedure and the risk of colorectal cancer in the general population, even in the absence of a family history, may help improve adherence to screening colonoscopy.

POST-POLYPECTOMY SURVEILLANCE: OFTEN TOO SOON, TOO FREQUENT

After a polyp or polyps are discovered on colonoscopy, many patients are being told to come back for repeat colonoscopy unnecessarily soon,27,28 thus diverting a scarce resource away from patients who may derive the most benefit—ie, those with high-risk polyps, those with a strong family history of colon cancer or an inherited predisposition to colon cancer, and those who have never undergone screening.

The following cases illustrate how current evidence-based guidelines can be applied to several different patients.

Case 2: ‘Three benign polyps’

A 51-year-old woman with no personal or family history of colorectal neoplasia calls her primary care physician after undergoing her first colonoscopy. The patient noted that she had had “three benign polyps removed.” She would like to know when her next colonoscopy should be.

The primary care physician obtains the patient’s colonoscopy report, which reveals that three polyps measuring 5 mm, 4 mm, and 4 mm were removed from the patient’s descending colon. The pathology report reveals that two of these polyps were tubular adenomas, and one of the 4-mm polyps was hyperplastic.

Case 3: A large tubulovillous polyp

A 46-year-old African American man with no personal or family history of colorectal neoplasia underwent his first colonoscopy 1 year ago. He had had a 1.5-cm pedunculated polyp removed in toto from his ascending colon. The pathologist characterized the polyp as “tubulovillous.”

Not all polyps are precancerous

The histopathology report helps the clinician determine the appropriate post-polypectomy surveillance interval (Table 2). Polyps are classified on the basis of their histologic features; the most common types of polyps are adenomas and hyperplastic polyps.

Adenomas are precursors to colorectal cancer, progressing via the widely recognized adenoma-carcinoma sequence.29 It is not unusual that both of our patients would have adenomatous polyps, since the prevalence of these polyps increases with age.30 Adenomas are detected in 11% of average-risk people ages 50 to 54, increasing to 33% to 50% in people 65 to 75 years old.31,32

Small, left-sided hyperplastic polyps, on the other hand, are considered nonneoplastic and do not require follow-up unless a patient meets the criteria for hyperplastic polyposis (Table 2). While current guidelines do not take into account hyperplastic polyps when determining postpolypectomy surveillance, the clinical significance and possible neoplastic potential of large and right-sided hyperplastic polyps is an area of active research.

Often, hyperplastic polyps are erroneously spoken of as “benign” when in fact they are not precancerous and are clinically insignificant. In fact, Boolchand et al27 found that 61% of primary care physicians would bring a patient with a single 6-mm hyperplastic polyp back for surveillance colonoscopy in 5 years or sooner. Current consensus guidelines do not recommend surveillance colonoscopy for the majority of patients with hyperplastic polyps. These individuals are not at an increased risk of colorectal cancer and should go back to average-risk screening recommendations, ie, colonoscopy in 10 years, the same interval as for the average-risk individual.33

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