Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they’re often referred to as colorectal cancers.
Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become colon cancers.
Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying polyps before they become colon cancer.
Signs and symptoms of colon cancer include:
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they’ll likely vary, depending on the cancer’s size and location in your large intestine.
If you notice any symptoms of colon cancer, such as blood in your stool or a persistent change in bowel habits, make an appointment with your doctor.
Talk to your doctor about when you should begin screening for colon cancer. Guidelines generally recommend colon cancer screenings begin at age 50. Your doctor may recommend more frequent or earlier screening if you have other risk factors, such as a family history of the disease.
Colon cancer most often begins as clumps of precancerous cells (polyps) on the inside lining of the colon. Polyps can appear mushroom-shaped, or they can be flat or recessed into the wall of the colon. Removing polyps before they become cancerous can prevent colon cancer.
Inherited gene mutations that increase the risk of colon cancer can be passed through families, but these inherited genes are linked to only a small percentage of colon cancers. Inherited gene mutations don’t make cancer inevitable, but they can increase an individual’s risk of cancer significantly.
The most common forms of inherited colon cancer syndromes are:
FAP, HNPCC and other, rarer inherited colon cancer syndromes can be detected through genetic testing.
Factors that may increase your risk of colon cancer include:
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one or more tests and procedures, including:
Once you’ve been diagnosed with colon cancer, your doctor will order tests to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.
Staging tests may include imaging procedures such as abdominal and chest CT scans. In many cases, the stage of your cancer may not be determined until after colon cancer surgery.
The stages of colon cancer are:
The type of treatment your doctor recommends will depend largely on the stage of your cancer. The three primary treatment options are: surgery, chemotherapy and radiation.
If your cancer is small, localized in a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy. Larger polyps may be removed using endoscopic mucosal resection. If the pathologist determines that it’s likely that the cancer was completely removed, there may be no need for additional treatment.
Polyps that can’t be removed during colonoscopy may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. The surgeon may also take samples from lymph nodes in the area where the cancer is located.
If your colon cancer has grown into or through your colon, your surgeon may recommend a partial colectomy to remove the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Nearby lymph nodes are usually also removed and tested for cancer.
Your surgeon is often able to reconnect the healthy portions of your colon or rectum. But when that’s not possible, for instance if the cancer is at the outlet of your rectum, you may need to have a permanent or temporary colostomy. This involves creating an opening in the wall of your abdomen from a portion of the remaining bowel for the elimination of body waste into a special bag. Sometimes the colostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.
If your cancer is very advanced or your overall health very poor, your surgeon may recommend an operation to relieve a blockage of your colon or other conditions in order to improve your symptoms. This surgery isn’t done to cure cancer, but instead to relieve signs and symptoms, such as bleeding and pain.
In specific cases where the cancer has spread only to the liver and if your overall health is otherwise good, your doctor may recommend surgery to remove the cancerous lesion from your liver. Chemotherapy may be used before or after this type of surgery. This treatment may improve your prognosis.
Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colon cancer is usually given after surgery if the cancer has spread to the lymph nodes. In this way, chemotherapy may help reduce the risk of cancer recurrence.
Chemotherapy can also be given to relieve symptoms of colon cancer that has spread to other areas of the body. Chemotherapy may be used before surgery to shrink the cancer before an operation. In people with rectal cancer, chemotherapy is typically used along with radiation therapy.
Radiation therapy uses powerful energy sources, such as X-rays, to kill cancer cells that might remain after surgery, to shrink large tumors before an operation so that they can be removed more easily, or to relieve symptoms of colon cancer and rectal cancer.
Radiation therapy is rarely used in early-stage colon cancer, but is a routine part of treating rectal cancer, especially if the cancer has penetrated through the wall of the rectum or traveled to nearby lymph nodes. Radiation therapy, usually combined with chemotherapy, may be used after surgery to reduce the risk that the cancer may recur in the area of the rectum where it began.
Drugs that target specific defects that allow cancer cells to grow are available to people with advanced colon cancer, including bevacizumab, cetuximab , Targeted drugs can be given along with chemotherapy or alone. Targeted drugs are typically reserved for people with advanced colon cancer.
Some people are helped by targeted drugs, while others are not. Researchers are working to determine who is most likely to benefit from targeted drugs. Until then, doctors carefully weigh the limited benefit of targeted drugs against the risk of side effects and the expensive cost when deciding whether to use these treatments.
People with an average risk of colon cancer can consider screening beginning at age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner.
Several screening options exist — each with its own benefits and drawbacks. Talk about your options with your doctor, and together you can decide which tests are appropriate for you.
You can take steps to reduce your risk of colon cancer by making changes in your everyday life. Take steps to:
Some treatments, including medications and surgery, have been found to reduce the risk of precancerous polyps or colon cancer. However, not enough evidence exists to recommend these medications to people who have an average risk of colon cancer. If you have an increased risk of colon cancer, discuss the benefits and risks of these preventive treatments with your doctor:
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