Colon Cancer

The vast majority of colon cancers develop from colon polyps called adenomas.  These polyps can develop in up to one-third of Americans by age 50. A smaller percentage of colon cancers can develop in patients who have inflammatory bowel disease.  The development of colon cancer is influenced by a person’s genes and by their environment.

Colon cancer can be associated with certain inherited genetic mutations, but more than 90% of colon cancers develop in patients without any known genetic predisposition.  We know that genes play a role, as the risk of developing colon cancer is higher if a parent or sibling has been diagnosed.  Nonetheless, the majority of colon cancers develop in people without a family history.

The risk of developing colon cancer can be reduced by living a healthy lifestyle.

People cannot change their genes, but there are some things that a person can do to reduce his or her risk of developing colon cancer:

• Eat a healthy, low-fat, high-fiber diet
• Avoid or limit eating red meat
• Exercise regularly
• Avoid tobacco
• Limit alcohol
• Take low-dose aspirin, calcium, vitamin D and folate

Colon cancer is one of the only truly preventable cancers.  Since most colon cancers develop from adenomatous polyps, removal of these polyps before they have a chance to mutate can prevent cancer.  The best way to find and remove these polyps is through colonoscopy.

Colon cancer is curable.  The chances of curing colon cancer are better when it is detected early.  In general, the cure for colon cancer is surgical removal of the tumor by removing a portion of the colon.  In most circumstances, patients that have surgical removal of a portion of the colon do NOT need a colostomy bag.

If the cancer is detected late and has spread beyond the colon to other parts of the body, this is called metastatic disease.  This occurs in approximately 25% of patients with colon cancer.  While the cure rate is not nearly as good for patients with metastatic disease, some of these patients can also be cured.  The best way to detect early cancer is through screening.  There are multiple methods of screening, including testing the stool for blood, DNA testing of stool and colonoscopy.

The vast majority of patients with colon cancer do not have any symptoms.  Some patients are diagnosed because they have anemia, or a low blood count.  Other patients can note a change in bowel habits, with alternating constipation and diarrhea.  Blood in the stool can be a sign of colon cancer.  Abdominal pain can also be a sign of colon cancer.  Any of these symptoms should prompt a patient to see their physician.

The vast majority of colon cancer patients have no pain.

Pain can result from one of two things:

1. If the colon cancer invades into surrounding structures, that can cause pain.  That type of pain is usually a localized dull ache.
2. If the cancer is causing blockage of the stool passing through the colon, the pain can be crampy and severe.  A tumor that causes a complete blockage of the colon leads to abdominal swelling and pain. 

Only a small percentage of colon polyps contain cancer.  Larger polyps have the highest risk of harboring a cancer.  A polyp that is larger than 2 cm (about an inch) has around a 20% chance of containing a focus of cancer.  Unless the entire polyp is removed and evaluated under a microscope, we can never be sure if a large polyp contains cancer.  For this reason, if the polyp cannot be removed with colonoscopy, we often recommend surgical removal of these polyps.

Tumors are found through screening tests or colonoscopy.

The stage of colon cancer is based on several factors.  Early stage cancers do not invade deeply into the wall of the colon.  With deeper invasion of the wall of the colon, the stage increases.  Stage III colon cancer means that the cancer has spread to lymph nodes, which increases the at risk for recurrence or spread to other organs.  Stage IV cancer means that it has metastasized, or spread to other organs including the liver and the lungs.

When colon cancer is diagnosed, the initial staging test is a CT scan.  That will tell us if the tumor has spread to other organs like the liver or lungs.  After the CT scan, the stage of the cancer is determined by the pathologist.  This type of staging is based on the surgical specimen.  Prior to removal of a colon cancer, it is not possible to determine the stage of the tumor because we need the pathology specimen. 

Surgical removal of the cancer is the mainstay of treatment.  In general, that means removal of a portion of the colon.  After removal of the tumor, the pathologic staging is completed.  It is this pathologic staging that determines if a patient will need chemotherapy.  In general, chemotherapy should be considered for stage III colon cancer.  For stage IV colon cancer, which has spread to other organs, chemotherapy is usually the first line of treatment.

It is very rare to need a colostomy bag following removal of a tumor, unless the tumor is causing a complete blockage of the colon.  Even in these cases, the colostomy bag is usually temporary.

Chemotherapy is recommended for higher stage colon cancers.  In general, the chemotherapy is relatively well tolerated.  The most bothersome side effect is usually nerve pain in the hands and feet.  Radiation therapy is rarely necessary in colon cancer.

Washington University Colon and Rectal can provide screening, care options and treatments for colon cancer. Meet our specialists below. 

Kerri Ohman, MD

Paul Wise, MD

Steven Hunt, MD

Matthew Silviera, MD

Matthew Mutch, MD