Colon Cancer

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Colon cancer

Alternative names

Colorectal cancer; Cancer - colon
Definition
Colon cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon). Such cancer is sometimes referred to as "colorectal cancer."

Other types of colon cancer such as lymphoma, carcinoid tumors, melanoma, and sarcomas are rare. In this article, use of the term "colon cancer" refers to colon carcinoma and not these rare types of colon cancer.

Causes, incidence, and risk factors

According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. (However, in almost all cases, early diagnosis can lead to a complete cure.)

There is no single cause for colon cancer. Nearly all colon cancers begin as benign polyps, which slowly develop into cancer.

You have a higher risk for colon cancer if you have:

Colorectal polyps
Cancer elsewhere in the body
A family history of colon cancer
Ulcerative colitis
Crohn's disease
Personal history of breast cancer
Certain genetic syndromes also increase the risk of developing colon cancer.

What you eat may play a role in your risk of colon cancer. Colon cancer may be associated with a high-fat, low-fiber diet and red meat. However, some studies found that the risk does not drop if you switch to a high-fiber diet, so the cause of the link is not yet clear.

Symptoms

Many cases of colon cancer have no symptoms. The following symptoms, however, may indicate colon cancer:

Diarrhea, constipation, or other change in bowel habits
Blood in the stool
Unexplained anemia
Abdominal pain and tenderness in the lower abdomen
Intestinal obstruction
Weight loss with no known reason
Narrow stools
With proper screening, colon cancer can be detected BEFORE the development of symptoms, when it is most curable.

Signs and tests
Your doctor will perform a physical exam and press on your belly area. The physical exam rarely shows any problems, although an abdominal mass may be felt. A rectal exam may reveal a mass in patients with rectal cancer, but not colon cancer.

Imaging tests to diagnose colorectal cancer include:

Colonoscopy
Sigmoidoscopy
Note: Only colonoscopy can see the entire colon.

A fecal occult blood test (FOBT) may detect small amounts of blood in the stool, which could suggest colon cancer. However, this test is often negative in patients with colon cancer. For this reason, a FOBT must be done along with colonoscopy or sigmoidoscopy. It is also important to note that a positive FOBT doesn't necessarily mean you have cancer.

A complete blood count may reveal show signs of anemia with low iron levels.

If your doctor learns that you do have colorectal cancer, additional tests will be done to see if the cancer has spread. This is called staging.

Stage 0: Very early cancer on the innermost layer of the intestine
Stage I: Cancer is in the inner layers of the colon
Stage II: Cancer has spread through the muscle wall of the colon
Stage III: Cancer has spread to the lymph nodes
Stage IV: Cancer that has spread to other organs
Treatment Return to top

Treatment depends partly on the stage of the cancer. In general, treatments may include:

Chemotherapy medicines to kill cancer cells
Surgery to remove cancer cells
Radiation therapy to destroy cancerous tissue
Stage 0 colon cancer may be treated by removing the cancer cells, often during a colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous. (See: Colon resection.)

There is some debate as to whether patients with stage II colon cancer should receive chemotherapy after surgery. You should discuss this with your oncologist.

Almost all patients with stage III colon cancer should receive chemotherapy after surgery for approximately 6 - 8 months. The chemotherapy drug 5-fluorouracil given has been shown to increase the chance of a cure in certain patients.

Chemotherapy is also used to treat patients with stage IV colon cancer. Irinotecan, oxaliplatin, and 5-fluorouracil are the three most commonly used drugs. You may receive just one type, or a combination of the drugs. Capecitabine is a chemotherapy drug taken by mouth, and is similar to 5-fluroruracil.

For patients with stage IV disease that has spread to the liver, various treatments directed specifically at the liver can be used. This may include cutting out the cancer, burning it (ablation), or freezing it (cryotherapy). Chemotherapy or radiation can sometimes be delivered directly into the liver.

While radiation therapy is occasionally used in patients with colon cancer, it is usually used in combination with chemotherapy for patients with stage III rectal cancer.

Support Groups
For additional resources and information, see colon cancer support groups.

Expectations (prognosis)

How well a patient does depends on many things, including the stage of the cancer. In general, when treated at an early stage, more than 90% of patients survive at least 5 years after their diagnosis. (This is called the 5-year survival rate.) However, only about 39% of colorectal cancer is found at an early stage. The 5-year survival rate drops considerably once the cancer has spread.

If the patient's colon cancer does not come back (recur) within 5 years, it is considered cured. Stage I, II, and III cancers are considered potentially curable. In most cases, stage IV cancer is not curable.

Complications

Cancer spreading to other organs or tissues (metastasis)
Recurrence of carcinoma within the colon
Development of a second primary colorectal cancer
Calling your health care provider

Colon cancer is, in almost all cases, a treatable disease if caught early. Removal of pre-cancerous polyps by colonoscopy essentially prevents colon cancer. If you are age 50 or older and have not yet had a colonoscopy, you should ask your health care provider about scheduling one. Early colon cancer usually has no symptoms, so screening by colonoscopy is important.

You should also call your health care provider if you have blood during a bowel movement, black, tar-like stools, or a change in bowel habits.

Prevention

The death rate for colon cancer has dropped in the last 15 years. This may be due to increased awareness and screening by colonoscopy. Colon cancer can almost always be caught in its earliest and most curable stages by colonoscopy. Almost all men and women age 50 and older should have a colonoscopy. Colonoscopy is almost always painless and most patients are asleep for the entire procedure.

For information on this procedure, see colonoscopy.

Dietary and lifestyle modifications are important. Some evidence suggests that low-fat and high-fiber diets may reduce your risk of colon cancer.

The U.S. Preventive Services Task Force recommends against taking aspirin or other anti-inflammatory medicines to prevent colon cancer if you have an average risk of the disease -- even if someone in your family has had the condition. Taking more than 300 mg a day of aspirin and similar drugs may cause dangerous gastrointestinal bleeding and heart problems in some people. Although low-dose aspirin may help reduce your risk of other conditions, such as heart disease, it does not lower the rate of colon cancer.

Cancer: Early Detection

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Why is it important to find cancer early?
For many types of cancer, it is easier to treat and cure the cancer if it is found early. There are many different types of cancer, but most cancers begin with abnormal cells growing out of control, forming a lump that's called a tumor. The tumor can continue to grow until the cancer begins to spread to other parts of the body. If the tumor is found when it is still very small, curing the cancer can be easy. However, the longer the tumor goes unnoticed, the greater the chance that the cancer has spread. This makes treatment more difficult.
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How do I know if I am at risk for cancer?
Talk to your doctor. He or she can help you understand your risk for cancer, especially if other members of your family have a history of cancer. Your doctor can also help you understand how your risk for cancer is affected by the following:
Using or having used tobacco products, such as cigarettes
Using alcohol
Having eaten a high-fat diet for most of your life
Being exposed to chemicals that can cause cancer
Being at risk for skin cancer
Depending on your age and your risk factors, your doctor may begin screening you for certain types of cancer. Screening means looking for cancer before it causes symptoms. Some doctors recommend that people who are at high risk or have a family history of cancer be screened regularly. The recommendations vary for different cancers.
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If I am a woman, what screening tests should I have?
To help find breast cancer early, you should begin by checking your breasts for lumps every month, beginning at about age 20. Your doctor can teach you how to check your breasts on your own. You should also have your doctor check your breasts every 1 to 2 years beginning when you're 30, and you should have a mammogram (an x-ray of your breasts) every 1 to 2 years beginning at age 40. If you have risk factors for breast cancer, such as a family history, your doctor may want you to have mammograms more often or start having them sooner.

To help find cervical cancer early, have regular Pap smears. During a Pap smear, your doctor takes a sample of cells from your cervix to be tested. You should have your first Pap smear when you start having sex or by age 18. Continue having a Pap smear once a year until you've had at least 3 normal ones. After this, you should have a Pap smear at least every 3 years, unless your doctor suggests that you need one more often. Keep having Pap smears throughout your life, even after menopause.
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If I am a man, what screening tests should I have?
To help find prostate cancer early, first talk to your doctor about your risk. Doctors don't all agree on whether screening is needed for men who aren't at high risk of prostate cancer.

The National Cancer Institute, the American Cancer Society, the U.S. Preventive Services Task Force and the American Academy of Family Physicians recommend that men talk to their doctors about whether screening is needed.

Your doctor may examine your prostate by putting a gloved, lubricated finger a few inches into your rectum to feel your prostate gland. This is called a digital rectal exam. A normal prostate feels firm and rubbery. If there are hard spots on the prostate, your doctor may suspect cancer.

Another way to check for prostate cancer is with a blood test called the PSA test. PSA is short for prostate-specific antigen. Men who have prostate cancer may have a higher level of PSA in their blood. However, the PSA level can also be high because of other, less serious causes such as infection.

To help find testicular cancer early, examine your testicles on a routine basis. If you find anything unusual during a self-exam (like a lump or swelling), see your doctor right away. The best time to do the exam is during or right after a shower or a bath. The warm water relaxes the skin on your scrotum and makes the exam easier. Your doctor can give you more specific information about checking your testicles.
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What about colorectal cancer?
Most colorectal cancers begin as a polyp (say “pahl-ip”). At first, a polyp is a small, harmless growth in the wall of the colon. However, as a polyp gets larger, it can develop into a cancer that grows and spreads. See your doctor if you have any of the following warning signs:
Bleeding from your rectum
Blood in your stool or in the toilet after you have a bowel movement
A change in the shape of your stool
Cramping pain in your lower stomach
A feeling of discomfort or an urge to have a bowel movement when there is no need to have one
A digital rectal exam is usually used along with another screening test to check for colorectal cancer. Tests used to screen for colorectal cancer include the following:
Fecal occult blood test (in which your stool is checked for blood that you can't see)
Flexible sigmoidoscopy (in which a tiny camera is inserted into your colon, allowing your doctor to look at the rectum and the lower part of your colon)
Double-contrast barium enema (for which you take an enema and have an x-ray to find abnormal spots)
Colonoscopy (similar to a flexible sigmoidoscopy, except the entire colon is examined)
Colorectal cancer is more common in older people, so doctors usually screen people after the age of 50 years. Some people have risk factors that make them more likely to get colorectal cancer at a young age. Screening should begin earlier in these people.

Talk to your family doctor to decide which screening tests you should have and how often you should be screened.
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What about skin cancer?
The best way to find skin cancer early is to keep an eye on your skin, especially moles. The ABCDE rule (see below) can help you remember what to look for when you're checking any moles on your skin. If you notice any of these signs, talk to your doctor right away.
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Signs of skin cancer: The ABCDE rule
A for asymmetry: A mole that, when divided in half, doesn't look the same on both sides.

B for border: A mole with edges that are blurry or jagged.

C for color: Changes in the color of a mole, including darkening, spread of color, loss of color, or the appearance of multiple colors such as blue, red, white, pink, purple or gray.

D for diameter: A mole larger than 1/4 inch in diameter.

E for elevation: A mole that is raised above the skin and has an uneven surface.



Colon Cancer

The large intestine or colon is a part of the gastrointestinal tract that makes and stores stool.

It includes the Ascending colon, Transverse colon, Descending colon and the Sigmoid colon.

The cause of cancer is an uncontrolled multiplication of cells lining the colon.

Before a true cancer develops, it usually begins as a non-cancerous growth called a polyp. Certain people can have multiple polyps in their colon which are inherited genetically.

Over a period of several years a polyp has the potential to become cancerous.

A cancerous polyp grows rapidly in size, eventually breaking through the wall of the colon and spreading through the tiny channels called lymph vessels.

The cancer can also spread through blood vessels to other parts of the body.

Symptoms of colon cancer are:

1. Blood in the stools
2. A change in bowel habits resulting in either more constipation or diarrhea than normal.
3. Abdominal pain.
4. Unintended weight loss

Medical investigations required to detect colon cancer are:

1. Colonoscopy
A long flexible tube called a colonscope is passed through the anus and manipulated to visualize the colon and identify the cancer growths.
2. Barium enema
3. CT scan or MRI
4. Routine blood tests

Treatment
Treatment varies depending on the stage of the disease. Some patients will need surgery to remove the diseased segment of the bowel followed by radiotherapy or chemotherapy