Colon Cancer: Risk Factors, Diagnosis and Treatment

Risk Factors

• Age: About 90 percent of cases occur in people over age 50, and incidence increases with age.
  
• Family history: Approximately 25 percent of patients have a positive family history. There is an increased risk if one or more first–degree relatives has colon cancer.
  
• Tobacco use
  
• Excessive alcohol use
  
• Coexisting diseases of the colon: Ulcerative colitis and Crohn’s disease increase the risk of colon cancer. There appears to be a higher risk with ulcerative colitis (as much as a five–fold to 15–fold increased risk) than with Crohn’s disease.
  
• Excess weight: People who are mildly or moderately obese appear to have a 10 to 35 percent greater risk. Severely obese persons (body mass index greater than 40) have a 45 percent greater risk.
  
• In contrast to these risk factors, certain dietary patterns and increased physical activity are associated with reduced colon cancer risk. Refer to Nutritional Considerations below.

Diagnosis

• History and physical examination should include a rectal exam and evaluation for occult rectal bleeding.
  
• Colonoscopy to visualize polyps or tumors is the most important test to diagnose colon cancers. It allows for biopsy of the lesions and can also remove growths. Colonoscopy is the best screening test to identify pre–cancers and early cancers of the colon.  It is recommended once every 10 years in all individuals over age 50, and earlier in individuals with heightened risk for the disease. “Virtual colonoscopy” using CT scan or MRI is under investigation, but has not yet been proven reliable.
  
• When colon cancer is diagnosed, patients usually require further testing to determine whether the cancer has spread beyond the colon. These tests include blood testing and CT scans of the thorax, abdomen, and pelvis.
  
• Blood testing is also often used to identify various tumor markers, which help to determine prognosis and evaluate for disease recurrence.
  

Treatment

• Surgery to remove the cancer is the definitive treatment.
  
• Advanced cancers require chemotherapy in addition to surgical removal of the tumor. In some cases, particularly rectal cancers, radiation is also used.
  
• If the cancer has spread to other areas of the body, further treatment will be necessary. This may include surgery, chemotherapy, or other modalities. In addition, a new medication called Avastin has recently been approved by the Food and Drug Administration as a first–line treatment for metastatic disease.