Colon Cancer

Definition

Colon cancer is cancer of the large intestine (colon), the lower part of the 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.

Symptoms

Signs and symptoms of colon cancer include:

• A change in bowel habits, including diarrhea or constipation or a change in the consistency of the stool for more than a couple of weeks
• Rectal bleeding or blood in the stool
• Persistent abdominal discomfort, such as cramps, gas or pain
• A feeling that the bowel doesn't empty completely
• Weakness or fatigue
• Unexplained weight loss

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 the large intestine

Causes

It's not clear what causes colon cancer in most cases. Doctors know that colon cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep the body functioning normally. But sometimes this growth gets out of control — cells continue dividing even when new cells aren't needed. In the colon and rectum, this exaggerated growth may cause precancerous cells to form in the lining of the intestine. Over a long period of time — spanning up to several years — some of these areas of abnormal cells may become cancerous.

1.  Precancerous growths in the colon
Colon cancer most often begins as clumps of precancerous cells (polyps) on the inside lining of the colon. Polyps can appear mushroom-shaped. Precancerous growths can also be flat or recessed into the wall of the colon (non-polypoid lesions). Non-polypoid lesions are more difficult to detect, but are less common. Removing polyps and non-polypoid lesions before they become cancerous can prevent colon cancer.
2.  Inherited gene mutations that increase the risk of 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. Inherited colon cancer syndromes include:

• Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes the development of  thousands of polyps in the lining of the colon and rectum. People with untreated FAP have a greatly increased risk of developing colon cancer before age 40.
• Hereditary non-polyposis colorectal cancer (HNPCC). HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC tend to develop colon cancer before age 50.

Both FAP and HNPCC can be detected through genetic testing.

Risk factors

Factors that may increase the risk of colon cancer include:

• Older age. About 90 percent of people diagnosed with colon cancer are older than 50. Colon cancer can occur in younger people, but it occurs much less frequently.
• African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
• A personal history of colorectal cancer or polyps. If a person already had colon cancer or adenomatous polyps, he has a greater risk of colon cancer in the future.
• Inflammatory intestinal conditions. Long-standing inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase the risk of colon cancer.
• Inherited syndromes that increase colon cancer risk. Genetic syndromes passed through generations can increase the risk of colon cancer. These syndromes include familial adenomatous polyposis and hereditary non-polyposis colorectal cancer, which is also known as Lynch syndrome.
• Family history of colon cancer and colon polyps. One is more likely to develop colon cancer if he has a parent, sibling or child with the disease. If more than one family member has colon cancer or rectal cancer, the risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
• Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat and processed meats.
• A sedentary lifestyle. If one is inactive, ha is more likely to develop colon cancer. Getting regular physical activity may reduce the risk of colon cancer.
• Diabetes. People with diabetes and insulin resistance may have an increased risk of colon cancer.
• Obesity. People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
• Smoking. People who smoke cigarettes may have an increased risk of colon cancer.
• Alcohol. Heavy use of alcohol may increase the risk of colon cancer.
• Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colon cancer.

Tests and diagnosis

• Blood tests. The doctor may order blood tests to better understand what may be causing the signs and symptoms, but there are no blood tests that can detect colon cancer. Blood tests may include a complete blood count and organ-function tests.

• Using a scope to examine the inside of the colon. Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view the entire colon and rectum. If any suspicious areas are found, the doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis.
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• Using dye and X-rays to make a picture of the colon. A barium enema allows the doctor to evaluate the entire colon with an X-ray. Barium, a contrast dye, is placed into the bowel in an enema form. During a double-contrast barium enema, air also is added. The barium fills and coats the lining of the bowel, creating a clear silhouette of the rectum, colon and sometimes a small portion of the small intestine.
• Using multiple CT images to create a picture of the colon. Virtual colonoscopy combines multiple computerized tomography (CT) images to create a detailed picture of the inside of the colon.

Treatments and drugs

The type of treatment the doctor recommends will depend largely on the stage of the cancer. The three primary treatment options are: surgery, chemotherapy and radiation.

Surgery for early-stage colon cancer
If the cancer is small, localized in a polyp and in a very early stage, the doctor may be able to remove it completely during a colonoscopy. If the pathologist determines that the cancer in the polyp doesn't involve the base — where the polyp is attached to the bowel wall — then there's a good chance that the cancer has been completely eliminated.
Some larger polyps may be removed using laparoscopic surgery. In this procedure, the surgeon performs the operation through several small incisions in the abdominal wall, inserting instruments with attached cameras that display the colon on a video monitor. He  may also take samples from lymph nodes in the area where the cancer is located.

Surgery for invasive colon cancer
If the colon cancer has grown into or through the colon, the surgeon may recommend a colectomy to remove the part of the 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.
The surgeon is often able to reconnect the healthy portions of the colon or rectum. But when that's not possible, for instance if the cancer is at the outlet of the rectum, one may need to have a permanent or temporary colostomy. This involves creating an opening in the wall of the 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 ther colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.

Surgery for advanced cancer
If  the cancer is very advanced or if the overall health is very poor, the surgeon may recommend an operation to relieve a blockage of the colon or other conditions in order to improve the symptoms. This type of surgery is referred to as palliative surgery. The goal of palliative surgery isn't to cure the cancer, but to relieve signs and symptoms, such as bleeding and pain.
In specific cases where the cancer has spread only to the liver and if the overall health is otherwise good, the doctor may recommend surgery to remove the cancerous lesion from the liver. Chemotherapy may be used before or after this type of surgery. This treatment may improve the prognosis.

Chemotherapy
Chemotherapy uses drugs to destroy cancer cells. Chemotherapy can be used to destroy cancer cells after surgery, to control tumor growth or to relieve symptoms of colon cancer. The doctor may recommend chemotherapy if the cancer has spread beyond the wall of the colon or if the cancer has spread to the lymph nodes. In people with rectal cancer, chemotherapy is typically used along with radiation therapy.

Radiation therapy
Radiation therapy uses powerful energy sources, such as X-rays, to kill any 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.

Targeted drug therapy
Drugs that target specific defects that allow cancer cells to proliferate are available to people with advanced colon cancer, including bevacizumab (Avastin), cetuximab (Erbitux) and panitumumab (Vectibix). 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.

Alternative medicine

No complementary or alternative treatments have been found to cure colon cancer.
Alternative treatments may help cope with a diagnosis of colon cancer. Nearly all people with cancer experience some distress. Common signs and symptoms of distress after  diagnosis might include sadness, anger, difficulty concentrating, difficulty sleeping and loss of appetite. Alternative treatments may help redirect thoughts away from fears, at least temporarily, to give some relief.

Alternative treatments that may help relieve distress include:

• Art therapy
• Dance or movement therapy
• Exercise
• Meditation
• Music therapy
• Relaxation exercises

Coping and support

A diagnosis of cancer can be extremely challenging. Even when a full recovery is likely, one may worry about a recurrence of the disease. But no matter what the concerns or prognosis, one is not alone. Here are some strategies and resources that may make dealing with cancer easier:

• Know what to expect. Find out everything needed to know about the cancer in order to make treatment decisions. Ask the doctor to tell you the type and stage of your cancer, as well as your treatment options and their side effects. The more you know, the more confident you'll be when it comes to making decisions about your own care. Look for information in your local library and on reliable Web sites on the Internet.
• Maintain a strong support system. Friends and family can be the best allies as you face your cancer diagnosis. They often want to help, so take them up on offers to make meals or provide transportation to and from appointments. Sometimes the concern and understanding of a formal support group or other cancer survivors can offer unique emotional support. You may also find you develop deep and lasting bonds with people who are going through the same things you are. There are also support groups for the families of cancer survivors.
• Set reasonable goals. Having goals helps you feel in control and can give you a sense of purpose. But don't choose goals you can't possibly reach. You may not be able to work a 40-hour week, for example, but you may be able to work at least half time. In fact, many people find that continuing to work can be helpful.
• Take time for yourself. Eating well, relaxing and getting enough rest can help combat the stress and fatigue of cancer. Also, plan ahead for the downtimes when you may need to rest more or limit what you do.

Prevention

Get screened for colon cancer
Regular colon cancer screening should begin at age 50 for people at average risk of colon cancer. 
Guidelines issued by the American Cancer Society include several options for colon cancer screening:

• Annual fecal occult blood testing
• Flexible sigmoidoscopy every five years
• Double-contrast barium enema every five years
• Colonoscopy every 10 years
• Virtual colonoscopy (CT colonography) every five years
• Stool DNA testing — new screening approach; test is available, but not certified by the Food and Drug Administration; research under way to increase accuracy and determine how often test should be done

More frequent or earlier screening may be recommended if one is at increased risk of colon cancer.

Make lifestyle changes to reduce the risk
One can take steps to reduce the risk of colon cancer by making changes in everyday life. Take steps to:

• Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
• Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women and two for men.
• Stop smoking. Talk to your doctor about ways to quit that may work for you.
• Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you've been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
• Maintain a healthy weight. If you have a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.

Colon cancer prevention for people with a high risk
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 and high risk of colon cancer.
Nonsteroidal anti-inflammatory drugs (NSAIDs) other than aspirin. This class of pain-relief medications includes drugs such as ibuprofen (Advil, Motrin, others) and naproxen (Aleve, others). Some studies have found NSAIDs may reduce the risk of precancerous polyps and colon cancer. But side effects include ulcers and gastrointestinal bleeding. Some NSAIDs have been linked to an increased risk of heart problems.

• Celecoxib (Celebrex). Celecoxib and other drugs known as COX-2 inhibitors work similarly to NSAIDs to provide pain relief. Some evidence suggests COX-2 drugs can reduce the risk of precancerous polyps in people who've been diagnosed with these polyps in the past. But COX-2 drugs carry a risk of heart problems, including heart attack. Two COX-2 inhibitor drugs were removed from the market because of these risks.
• Surgery to prevent cancer. In cases of rare, inherited syndromes such as familial adenomatous polyposis, or inflammatory bowel disease such as ulcerative colitis, the doctor may recommend removal of the entire colon and rectum in order to prevent cancer from occurring in the future.