Colorectal Cancer

Conditions A-Z - Colorectal Cancer

Anatomy of the colon

The colon is the large intestine. It has four sections.

The first section is called the ascending colon. It extends upward on the right side of the abdomen.

The second section is called the transverse colon since it goes across the body to the left side.

There it joins the third section, the descending colon, which continues downward on the left side.

The fourth section is known as the sigmoid colon because of its S-shape.

The sigmoid colon joins the rectum, which, in turn, joins the anus, or the opening where waste matter passes out of the body.

What is colorectal cancer?

Colorectal cancer is malignant cells found in the colon or rectum. The colon and the rectum are parts of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.

Excluding skin cancers, colorectal cancer is the third most common cancer in both men and women. The American Cancer Society estimates that about 140,000 colorectal cancer cases and about 50,000 deaths from colorectal cancer occur each year. The number of deaths due to colorectal cancer has decreased, which is attributed to increased screening and polyp removal and to improvements in cancer treatment.

What are the types of cancer in the colon and rectum?

A type of cancer called adenocarcinoma accounts for more than 95 percent of the cancers in the colon and rectum and is usually what is meant by the term colorectal cancer. It is the type we focus on in this section. There are other types of cancer that can be found in the colon and rectum, but they are rare.

Here is an overview of the types of cancer in the colon and rectum:

What are the symptoms of colorectal cancer?

The following are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently.

People who have any of the following symptoms should check with their doctors, especially if they are over 50 years old or have a personal or family history of the disease:

The symptoms of colorectal cancer may resemble other conditions, such as infections, hemorrhoids, and inflammatory bowel disease. It is also possible to have colon cancer and not have any symptoms. Always consult your health care provider for a diagnosis.

What are the risk factors for colorectal cancer?

Risk factors may include:

What is a risk factor?

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.

Although these factors can increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors. But, knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

What causes colorectal cancer?

The exact cause of most colorectal cancer is unknown, but the known risk factors listed above are the most likely causes. A small percentage of colorectal cancers are caused by inherited gene mutations. People with a family history of colorectal cancer may wish to consider genetic testing. The American Cancer Society suggests that anyone undergoing such tests have access to a doctor or geneticist qualified to explain the significance of these test results.

Prevention of colorectal cancer

Although the exact cause of colorectal cancer is not known, it may be possible to lower your risk of colorectal cancer with the following:

Methods of screening for colorectal cancer

Screening methods for colorectal cancer, for people who do not have any symptoms or strong risk factors, include the following:

Illustration demonstrating a colonoscopy, part 1
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Illustration demonstrating a colonoscopy, part 2
Screening guidelines for colorectal cancer
Colorectal cancer screening guidelines from the American Cancer Society for early detection include:
  • Beginning at age 50, both men and women should follow one of the examination schedules below:
    • Fecal occult blood test or fecal immunochemical test every year
    • Flexible sigmoidoscopy every five years
    • Double-contrast barium enema every five years
    • Colonoscopy every 10 years
    • CT colonography (virtual colonoscopy) every five years
  • People with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age and/or be screened more often:
    • Strong family history of colorectal cancer or polyps in a first-degree relative, especially in a parent or sibling before the age of 45 or in two first-degree relatives of any age
    • Family with hereditary colorectal cancer syndromes, such as familial adenomatous polyposis and hereditary nonpolyposis colon cancer
    • Personal history of colorectal cancer or adenomatous polyps
    • Personal history of chronic inflammatory bowel disease (Crohn's disease or ulcerative colitis)

Diagnostic procedures for colorectal cancer

If a person has symptoms that might be caused by colorectal cancer, the doctor will want to get a complete medical history and do a physical examination. The doctor may also do certain tests to look for cancer. Many of these tests are the same as those done to screen for colorectal cancer in people without symptoms.

What are the stages of colorectal cancer?

When colorectal cancer is diagnosed, tests will be performed to determine how much cancer is present, and if the cancer has spread from the colon or rectum to other parts of the body. This is called staging, and is an important step toward planning a treatment program. The stages for colorectal cancer are as follows:

Stage 0 (Cancer in situ) The cancer is found in the innermost lining of the colon or rectum.
Stage I (also called Dukes' A colon cancer) The cancer has spread beyond the innermost lining of the colon or rectum to the second and third layers. The cancer has not spread to the outer wall or outside of the colon or rectum.
Stage II (also called Dukes' B colon cancer) The cancer has spread through the wall or outside the colon or rectum to nearby tissue. However, the lymph nodes are not involved.
Stage III (also called Dukes' C colon cancer) The cancer has spread to nearby lymph nodes, but has not spread to other organs in the body.
Stage IV (also called Dukes' D colon cancer) The cancer has spread to other parts of the body, such as lungs.

Treatment for colorectal cancer

Specific treatment for colorectal cancer will be determined by your doctor based on:

After the colorectal cancer is diagnosed and staged, your doctor will recommend a treatment plan. Treatment may include:

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