Colonoscopy screening recommended for people with family history of colon cancer

A family history of colon cancer, also known as colorectal cancer or CRC, puts people at higher than average risk for developing the disease. March is National Colorectal Cancer Awareness Month and the American Society for Gastrointestinal Endoscopy (ASGE), which represents the doctors who specialize in endoscopy and colon cancer screening, is encouraging people to talk with their relatives to learn if they have a family history of colon cancer or polyps.

A polyp is a growth in the colon that may turn into cancer. For people with a family history of colon cancer or polyps, screening for colon cancer may be recommended at age 40 or younger. Even though having such a family history increases the risks for developing colon cancer, the majority of colon cancers appear in people without a family history of the disease; therefore, ASGE guidelines recommend that those people at average risk for the disease begin screening at age 50.

"Knowing your family's health history is important because studies have shown that people with a first-degree relative, a parent, sibling, or child, with colon cancer or polyps have a higher risk of developing the disease themselves," said Jacques Van Dam, MD, Ph.D., FASGE, president, American Society for Gastrointestinal Endoscopy. "Age is the single most important risk factor for colon cancer so guidelines recommend that all people age 50 and over be screened for colon cancer. Those with relatives who have been diagnosed with either colon cancer or polyps, however, may need to start screening beginning at age 40 or ten years younger than the age of the affected relative at the time of diagnosis, whichever is earlier. Colon cancer is a preventable disease and a recent report by leading cancer groups shows that death rates have dropped significantly since the 1970's, in part due to screening. ASGE urges people to talk with their family members about their health history and then discuss with their doctor an appropriate age to begin a colon cancer screening program."

About Colon Cancer

Colon cancer is found in the colon or the rectum, and usually develops very slowly, over a period of years, from a precancerous polyp.  A polyp is an abnormal growth of the tissue that lines the colon or rectum. The two main types of polyps are the adenomatous polyp and the hyperplastic polyp. An adenomatous polyp is a benign, precancerous growth that, if not removed, has the greatest risk of becoming cancer; a hyperplastic polyp is a benign growth with no potential to develop into cancer.

Because colon cancer develops slowly, screening for the disease is especially important as it allows the doctor to locate and remove polyps before they turn into cancer. For individuals at average risk, the ASGE recommends colonoscopy screening beginning at age 50 and repeating the procedure every ten years after a normal exam. For individuals with a family history, screening should begin at age 40, or at an age as recommended by their doctor. Colonoscopy is a particularly valuable method of colon cancer screening because it is the only method that allows for the detection and removal of precancerous polyps during the same exam and before the polyps turn into cancer, thereby preventing the colon cancer from occurring. Other screening methods, such as CT colonography or fecal occult blood tests, are less invasive and may also indicate the presence of precancerous and cancerous polyps; however, they do not allow the removal of polyps at the time of the exam so patients with polyps found during these exams are required to then undergo a subsequent colonoscopy.

People who have been diagnosed with polyps or colon cancer should notify their family members of the type of polyp or cancer found and their age at diagnosis. Both factors are important in assessing family members' risk and will help their doctor determine when the family members should begin screening for colon cancer. Individuals with their own history of polyps are also at risk for future polyps or cancer. Removal of an adenomatous polyp prevents that polyp from becoming cancerous, but the patient is still at risk to develop new polyps in the colon and will require more frequent follow-up exams. If the patient has a family history of colon cancer, the interval for their follow-up exam may be shortened. After a positive colonoscopy exam, the doctor will recommend when the patient should return for another colonoscopy.

Family History Screening Recommendations

The ASGE Guideline: Colorectal Cancer Screening and Surveillance (Gastrointest Endosc 2006;63:546-557) outlines recommendations for screening people with a family history of colon cancer and polyps:

  • Individuals with a family history of one or more first-degree relatives (sibling, parent or child) with sporadic colorectal cancer, regardless of age, should undergo colonoscopy beginning at age 40 years or ten years younger than the age of the affected relative at time of diagnosis, whichever is earlier.
  • Individuals with a first-degree relative aged less than 60 years at time of diagnosis of adenomatous polyps should undergo colonoscopy beginning at age 40 years or ten years younger than the age of the affected relative at the time of diagnosis, whichever is earlier.
  • In patients with a first-degree relative more than 60 years old at diagnosis of adenomatous polyps, the timing of screening colonoscopy should be individualized.

Rare Family History Conditions

In general, it is uncommon to be diagnosed with colon cancer under the age of 30 if there is no family history. However, there are two well-recognized hereditary syndromes in which cancer can develop in young people. The first is Familial Adenomatous Polyposis (FAP). This is a disease in which affected people develop hundreds to thousands of precancerous polyps in the colon. Unless the colon is removed, every one of these patients will develop colon cancer, usually by their late 30s. The disease is inherited directly from an affected parent (autosomal dominant inheritance), and the average age for polyp development in this syndrome is the mid-teens. If a family is known to have FAP, the affected parent and at-risk children may be screened for a gene mutation with a genetic test. Children who do not or cannot have genetic tests should start having sigmoidoscopies or colonoscopies at about ten or 12 years old and repeated every six to 12 months. Once numerous polyps are found, surgery to remove the colon is planned.

The other syndrome is Hereditary Non-Polyposis Colorectal Cancer (HNPCC), or Lynch syndrome. In this disorder, cancers also occur early and develop from polyps. The disease can also present at a later age. The standard recommendation for at-risk children of affected families is colonoscopy beginning at age 25 and repeated every two years. Genetic testing may also be helpful. There are specific recommendations for children in families with high rates of colon cancer. However, the specific syndrome must be known. It is very important for children from families with FAP or HNPCC to be seen by experts who have experience with these syndromes and where genetic counseling and testing services are available.

Colon Cancer Statistics

Each year, more than 145,000 people are diagnosed with colon cancer in the United States and almost 50,000 people die from the disease. It is the third-leading cause of cancer-related deaths in the U.S. in both men and women. A recent report showed that screening has helped to reduce incidence and death rates from the disease. The study, by the American Cancer Society, the National Cancer Institute, the Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries, on the status of cancer in the U.S. showed that from 1975 to 2000, the incidence rate dropped 22 percent and the death rate dropped 26 percent. These declines reflect the impact of increased colon cancer screening, changes in lifestyle and diet, and improved treatments. The report stated that "screening appears to have had a considerable impact on reducing CRC incidence and mortality."

While this is good news, it could be even better. Many people who should be screened are not actually being screened. The report also noted that if current trends persist, death rates from colon cancer could decline 36 percent by 2020 and there could be as much as a 50 percent decline if there are further improvements in risk factor control, screening and treatment.

Colon Cancer Symptoms

Colon cancer is often present in people without symptoms, making prevention and screening for colon cancer very important. A polyp may be found and removed even before it becomes cancerous or presents with symptoms; once symptoms appear, a colonoscopy is performed to aid in diagnosis, rather than screen for disease. The following signs or symptoms, however, might indicate colon cancer: blood in stools, narrower than normal stools, unexplained abdominal pain, unexplained change in bowel habits, unexplained anemia, and unexplained weight loss. These symptoms may be caused by other benign diseases such as hemorrhoids, inflammation in the colon or irritable bowel syndrome. The presence of these symptoms for more than a few days is an indication to talk with a gastrointestinal specialist about these symptoms and the patient's family history.


American Society for Gastrointestinal Endoscopy


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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