Encyclopedia

Definition

Colorectal cancer is a disease in which cancer cells grow in the colon and/or rectum. The colon and the rectum are parts of the large intestine, which is part of the digestive system.

Cancer occurs when cells in the body (in this case colon or rectum cells) divide without control or order. Normally, cells divide in a controlled manner. If cells keep dividing uncontrollably, a mass of tissue, called a growth or tumor, forms. The term cancer refers to malignant tumors, which can invade nearby tissue and spread to other parts of the body. A benign tumor does not invade or spread.

Colon Cancer

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Causes

The cause of colorectal cancer is unknown. However, research shows that certain risk factors are associated with the disease.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors include:

• Age: 50 or older
• Diets high in beef and fat, low in fiber
• Polyps (benign growths) in the colon and rectum (especially due to familial polyposis, an inherited condition)
• Personal history of colorectal cancer
• Family history of colorectal cancer, especially a parent, sibling, or child
• Ulcerative colitis (inflammation of the lining of the colon) or Crohn’s disease
• Long-term insulin use in people with type 2 diabetes (associated with an increased risk)
• Other risk factors include:
  • Obesity
  • High body mass index (BMI)
  • Physical inactivity
  • Diabetes
  • Smoking
  • Alcohol intake
  • Nightshift work
  • Ethnic background

Symptoms

Colorectal cancer often does not have any symptoms, but some symptoms associated with colorectal cancer include:

• A change in bowel habits such as diarrhea, constipation, or feeling that the bowel does not empty completely—lasting for more than a few days in people aged 50 and older
• Blood (either bright red or very dark) in the stool
• Stools that are narrower than usual
• Abdominal discomfort (frequent gas pains, bloating, fullness, and/or cramps)
• Unexplained weight loss
• Constant fatigue

These symptoms may also be caused by other, less serious health conditions. Anyone experiencing these symptoms should see a doctor.

Diagnosis

The doctor will ask about your symptoms and medical history and perform a physical exam.

Tests include:

• Digital rectal exam—use of a physician's gloved finger to examine the rectum for lumps or growths
• Fecal occult blood test—a test to check for hidden blood in the stool
• X-rays (using a barium enema)— pictures of the large intestine that show polyps or other changes
• Sigmoidoscopy—an examination of the lower colon using a lighted tube called a sigmoidoscope
• Colonoscopy—examination of the rectum and entire colon using a lighted tube .called a colonoscope
• Polypectomy—the removal of a polyp during a sigmoidoscopy or colonoscopy
• Biopsy—the removal of colon or rectal tissue to be tested for cancer cells
• Computerized tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET)—to identify the spread of the tumor outside the colon

Treatment

Once colon cancer is found, staging tests are performed to find out if the cancer has spread and, if so, to what extent. Treatment depends on the stage of the cancer.

Treatments include:

Prevention

The cause of most colorectal cancer is not known. However, it is possible to prevent many colon cancers by finding and removing polyps that could become cancerous. Beginning at age 50, both men and women at average risk for the development of colorectal cancer should follow one of the five screening options listed below:

• Yearly fecal occult blood test or fecal immunochemical test
• Flexible sigmoidoscopy every 3-5 years
• Yearly fecal occult blood test or fecal immunochemical test plus flexible sigmoidoscopy every 5 years
  • Of the above options, the American Cancer Society prefers the third one.
• Double contrast barium enema (x-rays of the colon and rectum) every 5 years
• Colonoscopy every 10 years

People with any of the following risk factors should begin colorectal cancer screening earlier at age 40 and/or undergo screening more often:

• Strong family history of colorectal cancer or polyps
• Known family history of hereditary colorectal cancer syndromes
• Personal history of colorectal cancer or adenomatous polyps
• Personal history of chronic inflammatory bowel disease