Colorectal Cancer

Medically Reviewed By William C. Lloyd III, MD, FACS

What is colorectal cancer?

Colorectal cancer is a cancer that grows within the colon, also called the large intestine or large bowel. Cancer that grows in the last section of the colon, the rectum, is often called rectal cancer, and cancer that grows in other areas of the colon is often referred to as colon cancer. Colorectal cancer most often develops in the lower areas of the large intestine.

Colorectal cancer is the third most common cancer in women and men in the United States (not including skin cancers). It is the second leading cause of cancer-related deaths in both sexes combined, according to the American Cancer Society (Source: ACS Trusted Source American Cancer Society Highly respected international organization Go to source ).

Did you know?

Despite the grim statistics for colorectal cancer, it is a highly curable cancer if it is caught early. Your best defense against colon cancer is regular medical care and screening tests. Screening tests include:

  • Digital rectal exam, in which a health care practitioner inserts a gloved, lubricated finger in the rectum to feel for abnormal growths or lumps

  • Fecal occult blood test, in which the feces are tested for hidden blood

  • Flexible sigmoidoscopy or colonoscopy, in which a physician inserts a small, flexible and lighted tube into the colon in order to view any polyps (abnormal growths) or other potential problems. Polyps may also be removed during this procedure.

If you dread the thought of undergoing testing for colorectal cancer, you are not alone. However, modern testing can be performed with a minimum of discomfort and dramatically increases the chances of catching and treating colorectal cancer in its earliest, most curable stage.
Colorectal cancer often develops from adenomatous intestinal polyps, noncancerous growths in the colon that can become malignant or cancerous over time. In their early stages, adenomatous intestinal polyps often produce no symptoms. As cancer develops, symptoms can include:

  • A change in bowel movements or habits, such as constipation or diarrhea, or a change in the usual color or texture of feces

  • Bloating and abdominal discomfort

  • Rectal bleeding or blood in the stool

    Untreated adenomatous intestinal polyps can develop into colorectal cancer. Colorectal cancer can grow through the intestinal wall and spread to other parts of the body, such as the liver and lungs, and become terminal. You can minimize the risk of life-threatening complications of colorectal cancer by seeking regular medical care and routine colorectal cancer screening tests.

    In addition, you should seek prompt medical care if you have symptoms of colorectal cancer, such as a change in bowel habits. Seek immediate medical care (call 911) if you have major rectal bleeding or bloody, black or tarry stool.

    What are the symptoms of colorectal cancer?

    Symptoms of colorectal cancer can vary among individuals. Some people experience no symptoms at all, especially in the early stages of the disease. In addition, colorectal cancer often develops from benign adenomatous intestinal polyps, which in themselves generally produce no symptoms.

    If adenomatous intestinal polyps are not diagnosed and removed promptly, they can become cancerous, resulting in symptoms that may include:

    • A change in bowel movements or habits, such as ongoing diarrhea, narrow (thin) stool, constipation, or runny stool

    • A feeling of not being able to empty the bowel completely

    • Abdominal discomfort or cramps

    • Bloating and gas

    • Fatigue

    • Rectal bleeding, blood in the stool, dark mucus in the stool, or pockets of blood in the stool

    • Unexpected weight loss

    Serious symptoms that might indicate a life-threatening condition

    As colorectal cancer grows, the wall of the colon gets thicker and hardens, and the growing tumor can block the colon, causing intestinal obstruction or rupture of the intestinal wall and a life-threatening infection called peritonitis. Seek immediate medical attention (call 911) if you, or someone you are with, have any of these symptoms:

    • Change in level of consciousness or alertness, such as passing out or unresponsiveness

    • Heavy rectal bleeding, or bloody, black or tarry stool

    • High fever (higher than 101 degrees Fahrenheit)

    • Severe abdominal pain

    What causes colorectal cancer?

    The exact cause of colorectal cancer is not known. However, research shows that multiple acquired changes to the genetic material in the cells lining the colon can lead to their uncontrolled growth and the formation of precancerous cells, which can eventually form polyps. The presence of adenomatous intestinal polyps that are not removed while still benign (not cancerous) significantly increases the risk of developing colorectal cancer. The initial event that alters the cells is not known in most cases, but some gene mutations that increase the risk of colorectal cancer can be inherited.

    What are the risk factors for colorectal cancer?

    A number of factors are thought to increase your chances of developing colorectal cancer. Not all people who are at risk for colorectal cancer will develop cancer.

    Risk factors for colorectal cancer include:

    • Abdominal radiation

    • Advanced age, especially age over 50 years

    • Diet high in red meats or processed meats (such as hot dogs or luncheon meats)

    • Family history of colorectal cancer

    • History of ulcerative colitis or Crohn’s disease

    • Obesity

    • Presence of adenomatous polyps (spontaneous or inherited)

    • Smoking

    Reducing your risk of colorectal cancer

    You can lower your risk of colorectal cancer by:

    • Being physically active and maintaining a healthy weight

    • Daily consumption of recommended doses of Vitamins B6, D and folic acid

    • Eating a diet that is low in red meats and high in fruits, vegetables, and whole grains

    • Not smoking or consuming excessive alcohol

    • Seeking regular medical care so that your health care provider can regularly screen for colorectal cancer and promptly diagnose and remove precancerous adenomatous intestinal polyps

    How is colorectal cancer treated?

    The goal of the treatment of colorectal cancer is to permanently cure the cancer or to bring about a complete remission of the disease. Remission means that there is no longer any sign of cancer in the body, although cancer may recur or relapse later.

    Colorectal cancer treatment plans use a multifaceted approach that is individualized to your age, medical history, coexisting diseases and conditions, and the type, location and stage of the disease.

    Colorectal cancer that is found in its very earliest stage and is limited to the inside of the polyp may be treated simply by removing the polyp. Cancer within the wall of the colon that has not spread to other organs outside of the colon may be treated by surgical removal of a section of colon containing the cancer. If colorectal cancer has gone beyond this stage or spread outside the colon, treatment may require a combination of surgery, chemotherapy, and radiation therapy.

    Colorectal cancer treatment may include an individualized combination of:

    • Chemotherapy for cases of colorectal cancer that have spread through the wall of the colon or to other organs such as the liver

    • Colectomy to surgically remove the cancerous section of the colon and surrounding areas. If possible, the remaining healthy sections of the colon are then rejoined to maintain a normal passageway for stool. In some cases, such as in some colorectal cancers of the lowest portion of the colon, this may not be possible, and a passageway for stool must be made through the abdominal wall. This is called a colostomy.

    • Dietary counseling to help people with cancer maintain their strength and nutritional status

    • Pain medications as needed

    • Palliative care to improve overall quality of life for families and patients with serious diseases

    • Participation in a clinical trial to test promising new therapies and treatments for colorectal cancer

    • Physical therapy to help strengthen the body, increase alertness, reduce fatigue, and improve functional ability during and after cancer treatment

    • Radiation therapy for cases of colorectal cancer that have spread through the colon wall

    • Removal of adenomatous intestinal polyps by colonoscopy or surgery

    • Testing of nearby lymph nodes for the presence of cancer cells, which indicates that the colorectal cancer has spread outside the colon

    Complementary treatments

    Some complementary treatments may help some people to better cope with colorectal cancer and its treatments. These treatments, sometimes referred to as alternative therapies, are used in conjunction with traditional medical treatments. Complementary treatments are not meant to substitute for traditional medical care. Be sure to notify your doctor if you are consuming nutritional supplements or homeopathic (nonprescription) remedies as they may interact with the prescribed medical therapy.

    Complementary treatments may include:

    • Acupuncture

    • Massage therapy

    • Nutritional dietary supplements, herbal remedies, tea beverages, and similar products

    • Yoga

    Hospice care

    In cases in which colorectal cancer has progressed to an advanced stage and has become unresponsive to treatment, the goal of treatment may shift away from curing the disease and focus on measures to keep a person comfortable and maximize the quality of life. Hospice care involves medically controlling pain and other symptoms while providing psychological and spiritual support as well as services to support the patient's family.

    In some cases, surgery may be performed to clear an intestinal obstruction and help relieve symptoms, but not necessarily as a curative treatment.

    What are the potential complications of colorectal cancer?

    Complications of colorectal cancer are life threatening. Complications of colorectal cancer are caused by rapid growth of abnormal cells that can grow through the wall of the intestine and travel through the bloodstream and lymphatic system to other areas of the body, most often the liver. There they can multiply rapidly and develop new malignant tumors that interfere with normal organ function.

    In addition, as colorectal cancer grows, the wall of the colon gets thicker and hardens, and the growing tumor can block the colon, causing intestinal obstruction or rupture of the intestinal wall and a life-threatening infection called peritonitis.

    You can best treat colorectal cancer and lower your risk of complications by seeking regular medical care and routine colorectal screening tests, and following the treatment plan you and your health care professional design specifically for you.

    Was this helpful?
    1. Colon and Rectal Cancer. National Cancer Institute, National Institutes of Health.
    2. Colon Cancer. PubMed Health, a service of the NLM from the NIH.
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    5. Colorectal Cancer. What are the risk factors for colorectal cancer? American Cancer Society.
    6. Colorectal Cancer. Treatment by stage of colorectal cancer. American Cancer Society.
    7. Siegel R, Naishadham D, Jemal A. Cancer statistics, 2013. CA Cancer J Clin 2013; 63:11.
    Medical Reviewer: William C. Lloyd III, MD, FACS
    Last Review Date: 2020 Nov 23
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