Educational Articles

Colon Cancer: Overview


Colon cancer is cancer that develops in the large intestine which is made up of the lower portion of the digestive system. Rectal cancer involves the last 10 to 12 cm of this large intestine. Together, they are often referred to as colorectal cancers, and they make up the second-leading cause of cancer-related deaths in the United States. colon cancer

Most colon cancer begin as small, noncancerous (benign) growth called adenomatous polyps. Over time, these polyps can grown and eventually become cancerous. In most cases, polyps may be small and produce few, if any, symptoms. As a result, it is important to get regular screening examination to help prevent colon cancer. When signs and symptoms of colon cancer may include a changes in bowel habits, blood in your stool, persistent cramping, gas or abdominal pain. colon polyp
Despite the relatively high number of cases and deaths, there is good news about colon cancer. It appears that the overall trend in colon cancer is improving with decreased incidence and death from this disease! 


Patients with colorectal cancer often have no symptoms, especially early on in the disease. When symptoms do appear, they will vary, depending on the size, location of the cancer. Bowel symptoms may result from a condition other than cancer, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), diverticulosis and diverticulitis.

You should see your doctor if you develop any of the following signs and symptoms:

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

Blood in your stool can be due to various conditions but also be a sign of cancer. For example, bright red blood you may notice on bathroom tissue often develop from hemorrhoids or minor tears (fissures) in your anus. In addition, certain foods, such as beets or red licorice, can turn your stools red. Iron supplements and some anti-diarrheal medications may cause black stools. Still, it is best to have any sign of blood or change in your stools checked promptly by your doctor.


Cancer affects your cells, the basic units of life. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But sometimes this growth gets out of control and — cells continue to divide even when new cells are not needed. In the colon and rectum, this uncontrolled growth causes precancerous polyps (adenomas, or adenomatous polyps) to form in the lining of your intestine. Over a long period of time — spanning up to several years — some of these polyps may become cancerous. In later stages of cancer, cancerous polyps may penetrate the colon walls and spread (metastasize) to nearby lymph nodes and other organs.

Colon polyps can occur anywhere in the large intestine, the muscular tube that forms the last part of your gastrointestinal tract. The colon comprises the upper 4 to 5 feet of your large intestine, and the rectum makes up the lower 4 to 5 inches. Your colon absorbs water, salt and other minerals from food and stores waste until it is eliminated from your body.

Polyps can be either mushroom-shaped or flat and may be large or small. There are also several different types of colon polyps. Among the most common are:
  • Adenomas. polyps have the potential to become cancerous and are usually removed during screening tests such as colonoscopy
  • Hyperplastic polyps. These polyps are not considered to carry risk for colorectal cancer.
  • Inflammatory polyps. These polyps may result from ulcerative colitis or other inflammatory condition of the colon but are generally not thought to be a strong risk for colon cancer.


Colon and rectal cancers can occur at any age. However, about 90 % of people with the disease are older than 50. Factors other than age that place you at a higher risk include:

  • Family history. You are more likely to develop colorectal cancer if you have a parent, sibling or child with the disease. The greater the number afflicted family members, the greater the risk. 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.

    Familial adenomatous polyposis (FAP) is a rare hereditary disorder that causes you to develop hundreds of polyps in the lining of your colon and rectum. If these go untreated, these patients will likely develop colon cancer by age 40. In most cases, genetic testing can help determine if you are at a risk of FAP. FAP may also cause noncancerous tumors to develop in other parts of your body, including your skin, bone and abdomen.

    Hereditary nonpolyposis colorectal cancer (HNPCC) is another hereditary disorder that can puts one at high risk of developing colon or rectal cancer at an early age. However, unlike FAP, you may have relatively few polyps.
    Patients of Jewish and of Eastern European descent, partucularly Ashkenazi Jews ,may have an inherited tendency to develop colon cancer or rectal cancer. 
  • Diet. Colon and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research is still occurring in this area. However, high-fiber, low-fat diets have additional health benefits apart from a potential connection to colorectal cancer prevention.
  • A sedentary lifestyle. Inactive people are more likely to develop colorectal cancer. This may be because when you are inactive, waste stays in your colon longer. Getting regular physical activity may reduce your risk.
  • Diabetes. Diabetics have up to a 40 percent increased risk of developing colorectal cancer.
  • Smoking. Smoking causes up to 10% fatal colon cancers. Once diagnosed with colorectal cancer, smokers face a 30 % to 40% increased risk of dying of the disease.
  • Alcohol. Heavy use of alcohol may increase your odds of colorectal cancer.
  • A personal history of colorectal cancer or polyps. Persons who have already had colorectal cancer or adenomatous polyps, have a greater risk of colorectal cancer in the future.



Most colon cancers develop from adenomatous polyps. Screening is essential for detecting polyps before they become cancerous. Colonoscopies/sigmoidoscopies help detect colorectal cancer in its early stages. Many people may be embarrassed by the screening procedures, worried about discomfort or afraid of the results. Try not to let these concerns stand in your way. Most procedures are only moderately uncomfortable. Working with a doctor you like and trust can ease your embarrassment. 

Common screening and diagnostic procedures include the following:

  • Digital rectal exam. In this office exam, your doctor uses a gloved finger to check the first few inches of your rectum for large polyps and cancers. Although safe and painless, the exam is limited to your lower rectum and does not detect problems with your upper rectum and colon. In addition, it is difficult for your doctor to feel small polyps.

  • Fecal occult (hidden) blood test.  This test checks a sample of your stool for blood. It can be performed in your doctor's office, but you are usually given a kit that explains how to collect the sample at home. You then return the sample to a lab or your doctor's office to be checked. Unfortunately, not all cancers bleed, and those that do often bleed intermittently. Furthermore, most polyps do not bleed. This can result in a false negative test result. Conversely, if blood shows up in your stool, it may be the result of hemorrhoids or an intestinal condition other than cancer. For these reasons, many doctors recommend other screening methods instead of, or in addition to, fecal occult blood tests.

  • Flexible sigmoidoscopy. In this test, your doctor uses a flexible, slender and lighted tube to examine your rectum and sigmoid — approximately the last 2 feet of your colon. The test usually takes just a few minutes. It can sometimes be uncomfortable, and there is a slight risk of perforating the colon wall. If a polyp or colon cancer is found during this exam, your doctor will recommend a colonoscopy to look at the entire colon and remove any polyps that are present for examination under a microscope.

  • Barium enema. This diagnostic test allows your doctor to evaluate your entire large intestine with an X-ray. Barium, a contrast dye, is placed into your bowel in an enema form. During a double contrast barium enema, air is also added. The barium fills and coats the lining of the bowel, creating a clear silhouette of your rectum, colon and sometimes a small portion of your small intestine. There is also a slight risk of perforating the colon wall and the test has a significantly high rate of missing important lesions. A flexible sigmoidoscopy is often done in addition to the barium enema to aid in detecting small polyps that a barium enema X-ray may miss. 

  • Colonoscopy. This procedure is the most sensitive test for colon cancer, rectal cancer and polyps. Colonoscopy is similar to flexible sigmoidoscopy, but the instrument used — a colonoscope, which is a long, flexible and slender tube attached to a video camera and monitor — allows your doctor to view your entire colon and rectum. If any polyps are found during the exam, your doctor may remove them immediately or take tissue samples (biopsies) for analysis. This is done through the colonoscope and is painless. If you have adenomatous polyps, especially those larger than 5 millimeters in diameter, you'll need careful screening in the future. You may receive a mild sedative to make you more comfortable. Preparation for the procedure involves drinking a large amount of fluid containing a laxative to clean out your colon — enemas are no longer necessary. Major risks of diagnostic colonoscopy include hemorrhage and perforation of the colon wall, but these are extremely rare and occur in less than 1 in 1,000.
  • Genetic testing. If you have a family history of colorectal cancer, you may be a candidate for genetic testing. This blood test may help determine if you're at increased risk of colon cancer or rectal cancer, but it's not without drawbacks. The results can be ambiguous, and the presence of a defective gene doesn't necessarily mean you'll develop cancer. Knowing you have a genetic predisposition can alert you to the need for regular screening. Still, you'll also want to consider the psychological impact of what the test may reveal. Knowing you may develop cancer affects not only your own life, but also the lives of everyone close to you. Genetic testing for children is even more complex and problematic. It's best if you discuss all of the ramifications of genetic testing with your doctor or a medical geneticist.
  • New technologies. In the future, new technologies, such as virtual colonoscopy, may make colon screening safer, more comfortable and less invasive. In virtual colonoscopy, you have a two-minute computerized tomography scan, a highly sensitive X-ray of your colon. Then, using computer imaging, your doctor rotates this X-ray in order to view every part of your colon without actually going inside. Before the scan, your intestine is cleared of any stool, but researchers are looking into whether the scan can be done successfully without the usual bowel preparation. Although virtual colonoscopy potentially is a tremendous step forward, it's currently much less accurate than regular colonoscopy and doesn't allow your doctor to remove polyps or take tissue samples. This test is also not widely available. Another new test checks a stool sample for DNA from abnormal cells. A clinical trial of this test by the National Cancer Institute is under way.
  • After a diagnosis of colorectal cancer, your doctor will then also "stage" your cancer. Staging helps determine how well you will do and what treatments are most appropriate for you. In both cases, the size of your tumor is not as important as how far your cancer has spread (metastasized). People being treated for colorectal cancer have a five-year survival rate higher than 90% if treated in an early stage, before it has spread. When cancer has spread to lymph nodes or nearby organs, the survival rate drops to less than 65%. The stages are: 
  • Stage 0. The cancer is in the earliest stage. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage of cancer may also be called carcinoma in situ (CIS).

  • Stage I. The cancer has grown through the mucosa but has not spread beyond the colon wall or rectum.

  • Stage II. The cancer has grown through the wall of the colon or rectum but has not spread to nearby lymph nodes.

  • Stage III. The cancer has invaded nearby lymph nodes but is not affecting other parts of the body yet.

  • Stage IV. Cancer has spread to distant sites or organs (common sites are the liver, lung, the membrane lining of the abdominal cavity, or ovaries).

  • Recurrent. This means the cancer has come back after treatment. It may recur in the colon, rectum or other part of the body. 



    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. Surgery (colectomy) is the main treatment for colorectal cancer. How much of your colon is removed and whether other therapies, such as radiation or chemotherapy, are an option for you depend on how far the cancer has penetrated into the wall of your bowel and whether it has spread to your lymph nodes or other parts of your body.

    Surgical procedures: The surgeon removes the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer to help ensure that no cancer remains. Nearby lymph nodes are usually also removed and tested for cancer. The surgeon is often able to reconnect the healthy portions of your colon or rectum, but sometimes that is not possible. For example, 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 wastes 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. 

    In cases of rare, inherited syndromes such as familial adenomatous polyposis, or inflammatory bowel disease(IBD) such as ulcerative colitis, you may need removal of your entire colon and rectum as a prophylactic measure. Then, in a procedure known as ileal pouch-anal anastomosis, your surgeon will likely construct a pouch from the end of your small intestine that attaches directly to your anus. This allows you to expel waste normally, although you may have several watery bowel movements a day. 

    Side effects of colon cancer surgery may include short-term pain and tenderness, and temporary constipation or diarrhea. If you have a colostomy, you may develop an irritation on the skin around the opening (stoma).

    If your cancer is small, localized in a polyp and in a very early stage, your surgeon may be able to remove it completely during a colonoscopy. If the pathologist determines that the cancer in the polyp does not involve the base — where the polyp is attached to the bowel wall — then there is a good chance that the cancer has been completely eliminated. 

    Some larger polyps may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several tiny incisions in your abdominal wall, using small instruments with attached cameras that display your colon on a video monitor. The doctor can take samples from the lymph nodes that drain the area where the cancer is located. Studies  have found that people undergoing this procedure need less pain medication and leave the hospital a day earlier on average. Also, people who have this procedure do not have higher rates of recurrence than those who choose the open surgical procedure. 

    If your cancer is advanced or your health is poor, only a small portion of your colon or rectum may be removed. This is not as effective as surgeries that remove more tissue. Doctors mainly do palliative surgery (non-curative) to relieve blockages or bleeding. 

    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 colorectal cancer. A doctor may recommend chemotherapy if your cancer has spread beyond the wall of the colon. In some cases, chemotherapy is used along with radiation therapy. 

    Possible side effects of chemotherapy include nausea and vomiting , mouth sores, fatigue, hair loss and diarrhea. If your doctor suggests aggressive treatment with multiple drugs, be sure you understand the side effects and risks as well as the potential benefits. If you are taking an oral chemotherapy medication, be sure you know the side effects to watch out for and report them to your doctor promptly.

    Radiation therapy Radiation therapy uses 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 colorectal cancer. The goal of therapy is to damage the tumor without harming the surrounding tissue. If your cancer has spread through the wall of the rectum, your doctor may recommend radiation treatments in combination with chemotherapy after surgery. This may help prevent cancer from reappearing in the same place. Side effects of radiation therapy may include diarrhea, rectal bleeding, fatigue, loss of appetite and nausea. 

    Biologics Recently, several new drugs from a new class of medications called biologics have been used to treat colorectal cancer by inhibiting the action of the cancer cells' growth factor. The drugs bevacizumab (Avastin) and cetuximab (Erbitux) are used in people with colon cancerthat has spread (metastatic cancer). Avastin is used in conjunction with standard chemotherapy and in a clinical trial added an average of five months to the study participants' survival time. Erbitux can be given on its own or in combination with the chemotherapy drug irinotecan (Camptosar). It has been shown to slow tumor growth and even shrink tumors, but there is currently no evidence showing that Erbitux can prolong survival. As more evidence mounts in this new area of research, doctors can better counsel their patients regarding the role of biologics in cancer treatment.  


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