Colon cancer is caused by colon cells growing out of control. As the number of cells grows, they form a tumor. Most colon tumors start when normal colon tissue forms an adenomatous polyp. As the polyp grows larger, a tumor is formed. Colon cancer that has spread from the colon to another part of the body is called metastatic cancer.

Risk Factors

Risk factors for colon cancer are:

Personal or family history of colon cancer, polyps, or inherited colon cancer syndromes (such as FAP and HNPCC / Lynch Syndrome).
History of ulcerative colitis or Crohn’s disease.
Lifestyle factors, such as a diet high in fat and red meat and low in fruits and vegetables, high caloric intake, inactivity, and obesity.
African American background.

Screening

Screening for colon cancer uses tests that screen for just cancer and tests that screen for both polyps and cancer. Tests that screen for polyps and cancer are:

Flexible Sigmoidoscopy.
Colonoscopy.
Double-contrast barium enema.
CT colonography (virtual colonoscopy).

Tests that screen mainly for cancer are:

Stool testing for blood.
Stool testing for DNA.

Talk to your provider about the age when you should start screening and which tests are right for you.

Signs & Symptoms of Colon Cancer

The early stages of colon cancer may not have any symptoms. As a polyp grows into a tumor, it can bleed or block (obstruct) the colon, which can cause symptoms:

Bleeding from the rectum.
Blood in the stool or toilet after a bowel movement.
A change in the shape of the stool, such as thinning.
Cramping pain in the abdomen (belly).
Feeling the need to have a bowel movement when you don’t really have to.

Diagnosis of Colon Cancer

If a screening test finds colon cancer, your provider will order tests to figure out the extent of the tumor. These tests may be:

CT scan.
MRI.
PET/CT scan.
Blood work.
Biopsy of the tumor or polyp.

A pathology report goes over the results of the biopsy and is sent to your healthcare provider. This report is an important part of planning your treatment. You can ask for a copy of your report for your records.

Staging Colon Cancer

To guide treatment, colon cancer is "staged." The stage is based on:

Where and how big the tumor is.
If cancer cells are found in the lymph nodes.
If cancer cells are found in other areas of the body.

Stage ranges from stage I (1) to stage IV (4). The stage and type of colon cancer will help guide your treatment plan.

Treatment

Often, the following treatments are used:

Surgery is the most used treatment. During surgery, a polyp and nearby tissue may be removed. Sometimes, the tumor, nearby tissues, and lymph nodes are removed and the two ends of the remaining colon are reconnected. If it is not possible to reconnect the colon, a colostomy is created.
Chemotherapy may be given after surgery to prevent the cancer from coming back (recurrence).
Targeted therapy, medications that work against a certain target, can be used to treat some types of colon cancer.
Radiation and interventional radiology procedures can be used to treat areas in the body where colon cancer has spread.

Colon Cancer: Staging and Treatment

Colorectal Cancer Screening

Colon, Rectal and Anal Cancer: Frequently Asked Questions