DEAR MAYO CLINIC:

Are the symptoms and causes of colon cancer in people in their 30s and 40s different than the symptoms and causes of colon cancer in older people?

ANSWER:

Colon cancer symptoms are similar in younger and older people. Because the large majority of colon cancers occur in people older than 50, however, the disease may go undetected in those who are younger until the cancer is more advanced. Timely screening for people at high risk for colon cancer, along with prompt assessment of any worrisome symptoms, is critical to early diagnosis and effective treatment for colon cancer.

In many cases, the exact cause of colon cancer can't be identified. Age is the most significant factor that can increase a person's risk for developing the disease. About 90 percent of people diagnosed with colon cancer are older than 50. Yet, a variety of hereditary and environmental factors also can increase a person's risk. When people get colon cancer in their 30s or 40s, hereditary factors are more likely to be the cause. Inherited disorders, such as familial adenomatous polyposis and Lynch syndrome (hereditary nonpolyposis colorectal cancer), are uncommon but can substantially increase the risk of colon cancer. Any individual, regardless of age, is also more likely to develop colon cancer if a parent, sibling or child has had the disease.

In addition to age and family medical history, risk factors for colon cancer include being African-American; having an inflammatory intestinal condition, such as ulcerative colitis or Crohn's disease; eating a high-fat diet; being inactive; obesity; smoking; heavy alcohol use; and having diabetes.

Diagnosing colon cancer in its earliest stages, before symptoms arise, can significantly increase the chances that the cancer can be successfully treated. Several options for colon cancer screening exist, including colonoscopy, CT colonography (virtual colonoscopy), fecal occult blood testing, flexible sigmoidoscopy barium enema and stool DNA testing. Because most colon cancers occur in older people, routine screening typically does not begin until age 50. For those with genetic risk factors, a positive family history of colon cancer, or other significant risk factors, screening usually begins a decade earlier at age 40.

Population studies show that colon cancers are occurring at increasing rates in people younger than 50. Cases in younger people now account for more than 10 percent of all colon cancers. Environmental factors, changes in diet and lifestyle, and the national trend toward obesity may be contributing to this rise. Also, younger-onset colon cancer appears to affect African-Americans more often than other groups.

The most common symptoms of colon cancer are rectal bleeding and lower abdominal cramping. Other telltale symptoms may include a change in stool consistency, constipation, diarrhea or weight loss. Blood tests that reveal new-onset anemia can often signal the presence of a colon tumor.

Unfortunately, colon cancer often is not considered as a cause of such symptoms in people who are younger than 50. As a consequence, colon cancer diagnosis can be delayed. Statistics show that colon cancer tends to be diagnosed at later stages in young people. Therefore, it's very important for anyone who experiences symptoms of colon cancer -- especially rectal bleeding and persistent lower abdominal cramping -- to seek medical advice, regardless of age. --

David Ahlquist, M.D., Gastroenterology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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