Colon and Rectal Cancers - Diagnosis

Highlights	Prevention	Radiation Treatment
Introduction	Diagnosis	Follow-up Testing
Causes	Staging	Treatment for Metastasized Colorectal Cancer
Symptoms	Prognosis	Resources
Risk Factors	Surgery	References
Dietary Factors	Medications

Diagnosis

Colon and rectal cancers are diagnosed using the screening tests discussed below. These tests can detect precancerous polyps and colorectal cancers at stages early enough for complete removal and cure.

Unfortunately, only 30% to 40% of adults over 50 years old (mostly in the upper socioeconomic group) have regular screening tests that could detect a cancer early enough for curative treatment. A survey reported that many people are not screened because they are too embarrassed and revealed that they would rather lose months off their life than face these tests. Those who had already had the tests were willing to have them again if they saved one additional day of their lives. There is some debate about what is the best screening modality. However almost all experts agree that not enough people are screened and that if these tests were adopted with the same regularity as other screening tests, such as Pap smears, they would save many lives. It is especially important that anyone at increased risk or with symptoms, such as rectal bleeding, undergo testing.

General Screening Guidelines

Individuals should discuss with their physician the risks and benefits of all screening procedures. Some controversy exists over how often people without risk factors for cancer should be screened and which detection method should be used for them.

Guidelines for Adults Age 50 and Over with Average Risk

The following are the most recent expert screening guideline options for people at age 50 and over who have no symptoms and no family history of colon cancer (or possibly also no family history of benign polyps):

A fecal occult blood test (FOBT) every year and a flexible sigmoidoscopy every five years. A follow-up colonoscopy should be done if any questionable results are found in either test. (The FOBT should be conducted first, since sigmoidoscopy would be replaced by colonoscopy if findings were suspicious.)
Many medical experts are now recommending a colonoscopy every 10 years, replacing sigmoidoscopy at that interval.
Another alternative for viewing the entire colon is a barium enema every five years, although it is less clear if this screening test offers any survival advantages.

In spite of the importance of screening, a government survey reported that in 2001 less than half of adults over 50 had ever had either an FOBT or endoscopy (that is, either sigmoidoscopy or colonoscopy).

Choosing between Colonoscopy and Sigmoidoscopy. The choice between the use of colonoscopy and sigmoidoscopy for routine screening for older adults with average risk is, in fact, an area of intense debate. The issues are as follows:

Sigmoidoscopy is less costly, less invasive, quicker, and safer than colonoscopy. Although it allows inspection only of the left side of the colon, any abnormal findings from sigmoidoscopy trigger a full colonoscopy. Therefore, experts estimate that the use of sigmoidoscopy results in detecting 80% of all significant problems.
Colonoscopy is more sensitive than any other current screening methods for detecting colon cancer. If the goal is to maximally reduce the number of cancer cases regardless of cost, colonoscopy would be the preferred approach. A landmark 1993 study reported an approximate 90% reduction in colorectal cancers in patients with precancerous polyps who were regularly screened with colonoscopy and who had all colonic polyps removed. And, no deaths were reported from cancers that were detected during screening. Colonoscopy, however, is more costly than sigmoidoscopy and carries a slightly higher risk for complications.

There are 3 basic tests for colon cancer: a stool test (to check for blood); sigmoidoscopy (inspection of the lower colon; and colonoscopy (inspection of the entire colon). All 3 are effective in catching cancers in the early stages, when treatment is most beneficial.

Guidelines for Increased- and High-Risk Groups

Screening, particularly with colonoscopy, in increased- and high-risk populations can save lives.

Guidelines for Increased-Risk Groups. Anyone with first-degree relatives diagnosed with colon cancer younger than 60 or with two relatives who have been diagnosed with colon cancer at any age. Such individuals should consider beginning the standard screening regimen with a colonoscopy every five years beginning at age 40 or ten years before the youngest case in the family (whichever is earlier). Of note: a 2002 study suggested that people in this group who have a personal history of polyps should talk to their physician about having colonoscopy every three years.

Men of African descent (particularly from sub-Saharan Africa) are also considered to be at increased risk for colon cancer and should discuss similar screening guidelines with their doctor.

Guidelines for High-Risk Groups. The following guidelines may be specifically useful for specific high-risk groups.

People known to have the mutated hereditary nonpolyposis colorectal cancer (HNPCC) gene (e.g., MSH-2 or MLH-1). Frequent colonoscopy (for instance, every one to two years) beginning in early 20s. (Regular screening for other cancers, such as uterine cancer, is also reasonable.)
People known to have the mutated familial adenomatous polyposis (FAP) gene. Frequent screening with endoscopy (e.g., flexible sigmoidoscopy or colonoscopy) beginning in early puberty. Genetic testing is now recommended for family members of people with known FAP.
People with predisposing intestinal problems such as widespread and active ulcerative colitis or Crohn's disease. Annual screening with colonoscopy with biopsies of suspicious areas.

Guidelines for Follow-Up After Detection of Precancerous Polyps

Patients who have had a previous examination in which polyps were detected (and removed) should have a repeat colonoscopy one to three years later, depending on the size, number, and type of polyps removed.