Colorectal malignancy accounted for about 10 percent of cancer-related deaths last year in the United States. By the end of 1998, an estimated 131,600 new cases of colorectal cancer were diagnosed, and 56,500 persons died from the disease.[1]

When localized to the bowel, colorectal cancer is highly treatable and often curable. With early detection, the five-year survival rate for patients with this malignancy is 92 percent.[2] Although the incidence of colorectal cancer is increasing, the overall mortality rate is decreasing. Whether improved survival is a result of earlier detection, more accurate diagnosis, more effective treatment or the identification and removal of premalignant polyps is unclear.

A multidisciplinary panel of experts representing the American Cancer Society (ACS), the American College of Gastroenterology and the American Society of Gastrointestinal Endoscopists has made specific recommendations for the screening and surveillance of patients at average or increased risk for colorectal cancer (Table 1).[3] The American Academy of Family Physicians (AAFP) and the U.S. Preventive Services Task Force also recommend sigmoidoscopy, starting at 50 years of age. Interestingly, persons at increased risk account for only 25 percent of colorectal cancers.[3] Thus, most malignancies would be missed if screening were limited to the high-risk group.

TABLE 1
Guidelines for Colorectal Screening

Risk Category         Risk factors

Average risk     Age 50 years or older but
asymptomatic and without any
of the characteristics or situations
indicating increased risk

Increased risk   Close relative(s) have had colorectal
cancer or an adenomatous polyp
Family history of familial
adenomatous polyposis

Family history of hereditary
nonpolyposis colorectal cancer

History of adenomatous polyps

History of colorectal cancer

Inflammatory bowel disease

Risk Category        Recommendations

Average risk     Fecal occult blood screening yearly
Flexible sigmoidoscopy every 5 years or
colonoscopy every 10 years or double contrast
barium enema every 5 to 10 years

Increased risk   Same recommendations as above, but screening is
initiated when the patient is 40 years old

Genetic counseling/testing
In a gene carrier, flexible sigmoidoscopy every
12 months, beginning at puberty

Genetic counseling/testing
Examination of the entire colon every 1 to 2
years, starting when the patient is 20 to 30
years old

Examination of the entire colon yearly after the
patient is 40 years old

Colonoscopy 3 years after initial examination,
with subsequent examinations, depending on the
types of polyps detected

Complete examination 1 year after colon surgery;
if normal, reexamination of colon in 3 years; if
still normal, reexamination in 5 years

Surveillance colonoscopy every 1 to 2 years,
beginning after 8 years of disease in the
patient with pancolitis and after 15 years in
the patient with left colon involvement only

NOTE: These guidelines have not been endorsed by the American Academy of Family Physicians and the U.S. Preventive Services Task Force.

Information from Winawer SJ, Fletcher RH, Miller L, Godlee F, Stolar MH, Mulrow CD, et al. Colorectal cancer screening: clinical guidelines and rationale. Gastroenterology 1997;112:594-642 [Published erratum in Gastroenterology 1997;112:1422].

To date, no randomized, controlled trials have shown that flexible sigmoidoscopy reduces the mortality rate associated with colorectal cancer. However, in one case-control study[4] it was found that in patients screened with rigid sigmoidoscopy the risk of fatal distal colon cancer was only 30 percent of the risk in unscreened patients.

Flexible sigmoidoscopy is a valuable procedural skill for family physicians. Many physicians acquire this skill in residency training and thus are more likely to use it later in practice.[5] On January 1, 1998, Medicare began covering colorectal cancer screening. Physicians should now be able to convince more patients to undergo sigmoidoscopy.