Colon cancer

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 30, 2016
StartDiseasesColon cancer

Colon cancer is also referred to as colorectal cancer. Although it is not necessarily the same as rectal cancer, they frequently occur together. It may take several years for colon cancer to produce symptoms, and sometimes there are no symptoms. It is important for individuals to be aware of how to prevent this common type of cancer and to undergo regular screenings.


Definition & Facts

Colon cancer begins in the colon or rectum, which are part of the large intestine, all of which are components of the body's lower digestive system. Colorectal cancer frequently begins as a polyp, which is a growth that may develop on the inner wall of the rectum or colon. Over time, polyps can become cancerous; therefore, preventative measures to find polyps allow for their removal and the prevention of colon cancer.

Developing slowly, colon cancer typically grows over a period of 10 to 20 years. Colorectal cancer is the third most common type of cancer in women and men in the United States. With the use of diagnostic tools such as fecal occult blood tests and colonoscopies, deaths from colon cancer have decreased.

Symptoms & Complaints

Colorectal cancer symptoms vary and depend on the location of the cancer, if it has spread, and the size of the tumor. In the early stages of colorectal cancer there are typically no symptoms. Tumors associated with colon cancer tend to bleed or obstruct the intestine as they grow. Warning signs that should prompt a visit with a healthcare provider include:

Some individuals develop anemia related to blood loss. In these cases, excessive fatigue and weakness may be present as well. If the cancer metastasizes to other areas within the body additional symptoms may be present in the newly affected area, which are dependent on the location. The liver is the most common organ affected by the metastasis of colorectal cancer.


Colon cancer occurs when healthy cells within the colon become altered. Whereas healthy cells grow and divide in an orderly manner, cancerous cells continue to divide regardless if new cells aren't needed. This overgrowth of cancerous cells causes the invasion and destruction of nearby healthy tissue. Most often, colon cancer begins as a polyp, which is a mass of precancerous cells on the inside lining of the colon. As mentioned previously, over time, these polyps can become cancerous.

An individual's risk for developing colon cancer can be increased by the presence of inherited genetic mutations. While the presence of these genes significantly increase an individual's risk of cancer, they do not make cancer inevitable as they are only linked to a small percentage of colon cancers. The most common forms of these inherited conditions include:

  • Hereditary nonpolyposis colorectal cancer (HNPCC) – This condition increases an individual's risk of colorectal cancer and other cancers. Individuals with this syndrome tend to develop colorectal cancer before the age of 50.
  • Familial adenomatous polyposis (FAP) – Although rare, this condition causes the growth of numerous polyps within the lining of the colon and rectum, even thousands at times. Those who leave this condition untreated have a greatly increased risk of developing colon cancer before the age of 40.

Diagnosis & Tests

If an individual has symptoms that are characteristic of colorectal cancer his/her physician may recommend tests and procedures including:

  • Colonoscopy – This is a procedure done under light sedation. During the procedure a long, slender and flexible tube is used to examine the inside of the colon. Attached to this tube is a video camera and monitor so the entire colon and rectum can be viewed. If suspicious findings are noted, such as polyps, a physician can pass surgical instruments through the tube to take samples of the tissue for analysis (biopsy).
  • CT colonography – This procedure is also referred to as a virtual colonoscopy. During this test, multiple CT scan images are combined to create a detailed view of the inside of the colon. This testing is typically done on individuals who are unable to undergo the process of a colonoscopy.

Individuals that are confirmed to have colorectal cancer will undergo further testing to determine the stage (extent) of the cancer. This is necessary for determining appropriate treatments. A physician may recommend specific laboratory tests on a tissue sample to identify specific genes and proteins. This is done for the purpose of determining if an individual's treatment options could include a treatment called targeted therapy.

Staging tests can include imaging procedures such as a chest or abdominal CT scan. An MRI can also be used to produce detailed images that can be used to measure the size of the tumor. Prior to the scan, a special dye is used, which can help determine where the colorectal cancer has grown. However, in many cases, the stage of cancer may not be determined until surgery is performed for the colon cancer. There are four stages of colon cancer including:

  • Stage I – The cancer has grown enough to affect the superficial lining of the colon or rectum but has not spread beyond the wall of the colon or rectum.
  • Stage II – The cancer has either grown into or through the wall of the rectum or colon but has not affected lymph nodes nearby.
  • Stage III – The cancer has progressed further to invade nearby lymph nodes but other parts of the body are not affected.
  • Stage IV – The cancer has spread to other tissues or organs, such as the liver or lungs.

Treatment & Therapy

There are various forms of treatment available for colorectal cancer. Some treatments are standard and used currently, while others are being tested in clinical trials. There are six different types of standard treatment.

One standard treatment is the surgical removal of cancer. This is the most common treatment for all stages of colorectal cancer. The surgical procedure is dependent on the size of the cancer. If in the early stages, a local excision can be performed. This involves the insertion of a tube with a cutting tool through the rectum into the colon, where the cancer can be removed.

If the cancer is larger a resection of the colon may be necessary. During this surgical procedure, a physician will remove the cancer and a small amount of surrounding healthy tissue. During this time, lymph nodes near the colon are typically removed so they can be examined to determine if they contain cancer as well. Lastly, the physician may perform an anastomosis, which is the sewing together of healthy parts of the colon.

If the cancer was so extensive that the physician was unable to sew healthy parts of the colon together, a procedure called a colostomy is performed. During this procedure an opening is made on the outside of the body for stool to pass through and a bag is placed around the opening to collect the waste.

After these surgical procedures, even if the physician was able to remove all of the cancer seen, some individuals still undergo chemotherapy or radiation therapy to be sure any cancer cells that may be left are killed. Other standard treatments for colorectal cancer include:

Prevention & Prophylaxis

Individuals who are believed to have an average risk for the development of colorectal cancer should consider beginning regular screening at age 50. Those with an increased risk, such as having a family history of colon cancer, should speak to their physician about beginning screening sooner. Screening typically involves undergoing a colonoscopy. In addition to screening, being aware of risk factors is important so they can be avoided if possible. The following are risk factors that increase the risk of developing colorectal cancer:

In addition, taking protective measures to decrease the risk of colon cancer include being physically active, taking aspirin or combination hormone replacement therapy, and removal of polyps.