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Colon Cancer 

Introduction
Colon cancer is a common type of cancer.  Colon cancer occurs when cells in the interior lining of the colon or large intestine grow abnormally and out of control.  The exact cause of colon cancer is unknown.
 
In most cases, colon cancers begin as a benign or non-cancerous polyp.  A polyp is a small growth that projects out from the inside lining of the colon.  Not all polyps turn into cancer.  Polyps that turn into cancer typically take several years to do so.  Screening for colon cancer allows polyps to be detected and removed early, which may prevent the development of cancer.

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Anatomy

Your colon is located at the end part of your digestive system.  Whenever you eat and drink, food travels through your digestive system for processing.  Your body absorbs nutrients and removes waste products via your digestive system. 

When you eat, your tongue moves chewed food to the back of your throat.  When you swallow, the food moves into the opening of the esophagus.  Your esophagus is a tube that moves food from your throat to your stomach.  Muscles in your esophagus wall slowly squeeze the food toward your stomach.

Chemicals in your stomach begin to break down the food.  Your stomach processes the food you eat into a liquid form.  The processed liquid travels from your stomach to your small intestine.  The small intestine is a tube that is about 20-22 feet long and 1 ½ to 2 inches around. Your small intestine breaks down the liquid even further so that your body can absorb the nutrients from the food you ate. The remaining waste products from the small intestine travel to the large intestine.

Your large intestine, also called the large bowel, is a tube that is about 5 feet long and 3 or 4 inches around.  The large intestine is divided into sections, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, and anus.  The appendix is located on the cecum, but it does not serve a purpose in the digestive process. 

The first part of the colon absorbs water and nutrients from the waste products that come from the small intestine.  As the colon absorbs water from the waste product, the product becomes more solid and forms stool or feces.  The large intestine moves the stool into the sigmoid colon, where it may be stored before traveling to the rectum.  The rectum is the final 6-inch section of your large intestine.  No significant nutrient absorption occurs in the rectum or anal canal.  From the rectum, the stool moves through the anal canal.  It passes out of your body through your anus when you have a bowel movement.

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Causes
The exact cause of colon cancer is unknown.  Cancer occurs when cells in the interior lining of the colon grow abnormally and out of control, instead of dividing in an orderly manner.  Because the colon and rectum are both part of the large intestine, cancers are sometimes referred to together as “colorectal cancer,” although their treatments may differ.
 
In rare cases, colon cancer can develop as a result of genetic mutations.  However, the majority of colon cancers begin as a benign or non-cancerous polyp.  A polyp is a small growth that projects out from the inside mucus lining of the colon.  A type of polyp called an adenoma can turn into cancer.  Cancer in the cells that line the inside of the colon are called adenocarcinomas.  Adenocarcinomas are the most common type of colon cancer.  However, not all polyps turn into cancer.  Polyps that turn into cancer typically take several years to do so.

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Symptoms
Most people with early colon cancer do not have symptoms.  Symptoms tend to appear as colon cancer advances.  Some people do not develop any symptoms.  Symptoms may include changes in bowel movement patterns.  You may develop diarrhea, constipation, or narrow stools that last for more than a few days.  You may experience rectal bleeding or have blood in your stools.  However, it is also common for the stools to remain normal looking.  You may have the feeling that you need to have a bowel movement even after you have just completed one. 
 
You may also experience lower abdominal pain or cramps.  You may feel weak or tired.  Some people develop anemia, a decrease in red blood cells. 

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Diagnosis
Your doctor can diagnose colon cancer after reviewing your medical history and by conducting a physical examination.  You should tell your doctor about your symptoms and risk factors.  Your doctor will rule out other conditions with similar symptoms, such as hemorrhoids or infection.  There are several tests for colorectal cancer.
 
Your doctor will examine your abdomen to feel for growths or enlarged organs.  Your doctor may also perform a digital rectal examination.  A mass may be indicative of rectal cancer, but not colon cancer.
 
A stool blood test can detect small amounts of blood in your stool. The fecal occult blood test (FOBT) or the fecal immunochemical test (FIT) is commonly used.  You will receive a kit and instructions for taking a stool sample at home.  The kit is sent to a laboratory for testing.  If the test results are positive, your doctor may order a sigmoidoscopy or colonoscopy to identify the exact cause of bleeding.
 
A flexible sigmoidoscopy is used to view the rectum and part of the colon for cancer or polyps.  A sigmoidscope is a thin tube with a light and viewing instrument.  It is about two feet long.  The sigmoidscope is placed in the colon, through the anus.  This test can be uncomfortable, but should not be painful.
 
A colonoscopy is used to view the entire colon.  A colonoscopy is similar to a sigmoidscope, but it is much longer.  A colonoscopy allows a doctor to examine the colon for cancer or polyps.  A tissue sample or biopsy may also be taken with the colonoscopy.  A colonoscopy can be uncomfortable however you will receive medication to relax you for the test.
 
A virtual colonoscopy is a newer way to view the colon with a computed tomography (CT) scan.  A CT scan takes a series of images to compose a detailed picture.  A virtual colonoscopy involves filling the colon with air and then taking the CT scans.  The CT images construct a visual depiction of the interior of the colon.  The colon can also be viewed with a barium enema with air contrast test.  For this test, the barium, a chalky substance, and air are used to fill and expand the colon.  Next, X-rays are taken.  These tests can be uncomfortable.  Any abnormal results are followed up with a colonoscopy.
 
Your doctor may order blood tests to see if you have anemia.  Anemia is a condition that results from a low red blood cell count.  Some people with colorectal cancer develop anemia as a result of bleeding from a tumor. 
 
If your tests are positive for colorectal cancer, your doctor will order tests to determine if the cancer has spread to other parts of your body.  In some cases, cancer that originates in the colon can spread or metastasize to other organs.  Blood tests can assess your liver function.  CT scans and chest X-rays can see if the cancer has spread to the liver, lungs, or other organs.
 
If you have colon cancer, your doctor will determine what stage of growth your cancer is in and if it has spread or metastasized.  Your doctor will assign a number to label your cancer stage.  Staging is helpful for treatment planning and recovery prediction.  There are different systems for staging colon cancer, and you should make sure that you understand the system that your doctor is using.  The stages of colon cancer are most commonly labeled with the Roman numerals I through IV, with a higher number indicating a more serious cancer.  The stages of colon cancer, according to the American Cancer Society, are:
Stage 0:  The cancer has not grown beyond the inner lining of the colon.
Stage I:  The cancer has grown through several inner layers of the colon.
Stage II:  The cancer has grown through the wall of the colon and may extend to nearby tissues,
but it has not spread to the lymph nodes.
Stage III:  The cancer has grown through the colon and  to nearby lymph nodes, but it has not
spread to other parts of the body.
Stage IV:  The cancer has grown through the colon and has metastasized to distant
tissues and organs, such as the liver, lungs, peritoneum, or ovaries.

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Treatment
Your doctor may refer you to an Oncologist for treatment.  An Oncologist is a doctor with special training in cancer and cancer treatments.  Treatment for colon cancer depends on the stage of the cancer. 
 
Surgery is the primary treatment for colon cancer.  Surgery removes the cancerous mass from the body.  Advanced cancers may need adjuvant therapy or additional treatments.  Adjuvant therapies are used if there is a chance that cancer cells may exist outside of the surgical site or if there is a chance that the cancer might come back.
 
Adjuvant therapies for colon cancer include radiation therapy and chemotherapy.  Radiation therapy uses high-energy rays to destroy cancer cells.  Chemotherapy uses cancer-fighting drugs to destroy cancer cells.  There are several different types of radiation therapy and chemotherapy.  Treatments usually last for several weeks or months.  Your doctor will let you know what to expect.
 
Stage 0 colon cancer is treated with the surgical removal of the lesion or polyp.  The surgery is frequently done with the colonoscopy.  Stage I colon cancer can also be treated with surgery.  Stage I colon cancer may require the removal of the segment of the colon containing the cancer, after which the colon is reattached.  Stage 0 and Stage I colon cancers do not require additional therapy.
 
Stage II colon cancer is usually treated with surgical resection of  a portion of the colon.  In some cases radiation therapy or chemotherapy is recommended if the cancer has a high likelihood of returning.  Stage III colon cancer is first treated with surgical resection of the colon and then with chemotherapy.  In some cases, radiation may also be used.
 
Treatment of Stage IV colon cancer depends on how extensively the cancer has metastasized.  Treatment choices may also depend on the overall health of the individual.  The goal of Stage IV colon cancer treatments are to prevent complications, extend life, and to improve the quality of life.  Stage IV treatments are usually not curative in nature.  Stage IV colon cancer surgery is usually performed to prevent colon complications, such as a blockage.  In come cases a stent or tube is inserted through the cancer tumor to prevent or help manage blockages. 
 
Stage IV colon cancer surgery may involve resection of the colon or a colostomy.  A colostomy involves surgically creating an opening in the abdominal wall for the elimination of stools.  This diverts the process from the anus.  A colostomy may be necessary if the colon is extensively damaged.
 
Surgery in Stage IV also includes removing cancer metastases from other organs if possible.  Metastases may also be treated with nonsurgical methods, such as freezing or heating with microwaves.  Chemotherapy and/or radiation therapy may also be given.
 
In some cases, colon cancer returns after treatment.  This is termed “recurrent colon cancer.”  Recurrent colon cancer may come back near the original site or in distant organs.  It most commonly returns in the liver first.  Recurrent colon cancer may be treated with surgery and chemotherapy. 
 
If the colon cancer does not return in five years after treatment, it is considered cured.  Stage 0-III colon cancers are potentially curable.  In most cases, Stage IV colon cancer is not curable.  Your doctor will let you know what to expect.
 
The experience of cancer and cancer treatments can be an emotional process for people with cancer and their loved ones.  It is important that you receive emotional support.  Some people find comfort in their family, friends, co-workers, and place of worship.  Cancer support groups are another good option.  They can be a good source of information and support from people who understand what you are experiencing.  Ask your doctor about cancer support group locations in your area.   

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Prevention
In most cases, colon cancer is treatable if it is detected early.  The American Cancer Society recommends that people be screened for colon cancer beginning at age 50.  Screening may be warranted earlier for people with a history of polyps or inflammatory bowel disease, and a personal or family history of certain cancers.  Screening may include a fecal occult blood test, flexible sigmoidoscopy, colonoscopy, and barium enema testing.
 
If you have been diagnosed and treated for colon cancer, you will have regular follow-up appointments to check for recurrence.  Some studies suggest that lifestyle changes may be helpful as well.  These studies are not conclusive, but they suggest that eating fruits and vegetables that are high in fiber and reducing high-fat foods may reduce the risk of colorectal cancer.  Other studies suggest that vitamins or a diet containing folic acid or folate, vitamin D, magnesium, and calcium may help lower colorectal cancer risk.  Exercising for 30 minutes for five or more days during the week is also recommended.
 
Aspirin and similar medications may help reduce polyp formation in some people.  However, not everyone can tolerate the side effects of aspirin.  You should talk to your doctor before taking aspirin to see if it is right for you.

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Am I at Risk

Risk factors may increase your likelihood of developing colon cancer.  People with all of the risk factors may never develop the disease; however, the chance of developing colon cancer increases with the more risk factors you have.  You should tell your doctor about your risk factors and discuss your concerns.

Risk factors for colon cancer:

_____ People over the age of 50 are more likely to develop colon cancer.
_____ If you had colon cancer before, even if it was removed, you are at risk for developing colon cancer again.
_____ If you have had polyps in your colon or rectum you have an increased risk for cancer in your colon or rectum.  Numerous polyps or large polyps are associated with a higher risk. 
_____ Ulcerative colitis and Crohn’s Disease, digestive tract diseases, increase the risk for colon cancer.
_____ If you have family members that have colon or rectal cancer, especially before the age of 60, you are at a higher risk for colon cancer.
_____ Certain genetic syndromes in some families cause the development of hundreds of polyps in the colon.  The high number of polyps increases the risk of developing cancer.
_____ People who are Ashkenazi Jews or African American appear to have a higher risk of developing colon cancer than people of other ethnicity or racial backgrounds.
_____ What you eat may increase your risk for colon cancer, although the cause of the link is not clear.  Diets that are low in fiber, high in fat and animal products, such as meat, appear to increase the risk for colon cancer.
_____  People who do not exercise have a higher risk of developing colorectal cancer.
_____ People who are overweight have an increased chance of dying from colorectal cancer.
_____ People who smoke are more likely than non-smokers to die of colorectal cancer.
_____ Consuming a large amount of alcohol is linked with colorectal cancer.
 
Researchers suggest that people with diabetes, breast cancer, and testicular cancer may have a higher risk for developing colorectal cancer, although the results of such studies are not conclusive.  Researchers also suspect that long-term female night shift workers may also be at risk because of the role of light on body cell development, but more studies are needed.

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Complications
Metastases are a complication of Stage IV colon cancer.  This means that the cancer has grown through the colon and spread to distant tissues and organs.  Common sites for colon cancer metastases include the liver, lungs, peritoneum, or ovaries.  The cancer must be treated in the distant organs as well as in the colon.
 
Recurrent colon cancer can be a complication after treatment.  Recurrent colon cancer may return near the original site in the colon and in the distant organs, usually the liver first.  Recurrent colon cancer is ideally treated with surgery first along with radiation therapy.
 
The side effects of radiation therapy and chemotherapy can be harsh for some people.  The type of side effects you experience may depend on the type of radiation therapy or chemotherapy that you receive.  Tell your doctor about the side effects you experience.  In some instances, steps can be taken to relieve or reduce the amount of side effects. 
 
The side effects from chemotherapy may include temporary hair loss, nausea, vomiting, diarrhea, loss of appetite, mouth sores, rashes, fatigue, low blood counts, hand swelling, and foot swelling.  Most side effects subside after treatment.  Your hair will grow back, although it may look different. 
 
Potential side effects of radiation therapy include mild skin irritation, nausea, diarrhea, rectal irritation, bladder irritation, loss of bowel control, fatigue, vaginal irritation in women, and impotence in men.  Some of the side effects from radiation may be temporary, but others may persist and become permanent. 

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Advancements
Researchers are continually working on methods to prevent, detect, and treat colon cancer.  Researchers are working on chemoprevention, methods of using diet and medications to lower the risk of getting cancer.  Scientists are also studying the genetic changes that take place during cancer.  They hope to identify gene therapies that can correct such problems. 
 
In the area of immunotherapy, researchers are studying ways to boost a person’s immune system to fight colon cancer better.  Medications are also being studied that can detect fast and slow growing cancer cells.  Finally, researchers are looking for new ways to perfect the screening process for colon cancer and to inform the public about such screening methods.

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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on April 13th, 2016. For information on iHealthSpot’s other services including medical website design, visit www.iHealthSpot.com.