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Information About 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?

The colon and the rectum are part of the large intestine, which is part of the digestive system. Malignant tumors can be found in either the colon or rectum. The large bowel includes the first 6 feet of bowel, the colon, and the last 6 inches includes the rectum and the anal canal.

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.

Colorectal cancer is the third most common cancer in both men and women. It is estimated by the American Cancer Society that 106,370 colon and 40,570 rectal cancer cases are expected in 2004. However, the number of new cases of colorectal cancer, and the number of deaths due to colorectal cancer, have decreased, which is attributed to increased screening and polyp removal.

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 physicians, 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 physician 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 colorectal cancer is unknown. Age and health history can affect the risk of developing colorectal cancer. Approximately 25 percent of individuals with colorectal cancer have at least one relative with colorectal cancer, while 75 percent of cases are persons without a family history.

Approximately 5 percent to 6 percent of colorectal cancers are due to known predisposing genetic factors. This means that the majority of colorectal cancers are, in fact, not inherited. Specifically, 3 percent to 5 percent of all colorectal cancer is due to hereditary nonpolyposis colon cancer (HNPCC), while approximately 1 percent is due to familial adenomatous polyposis (FAP).

Persons 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 physician or geneticist qualified to explain the significance of the results.

Prevention of colorectal cancer:

Although the exact cause of colorectal cancer is not known, it is possible to reduce the risk of developing many colon cancers 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 should begin at age 50 and include the following:

Screening Guidelines for Colorectal Cancer

Colorectal cancer screening guidelines for 2004 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 (FOBT) every year
    • flexible sigmoidoscopy (FSIG) every five years
    • annual FOBT and FSIG every five years
    • double-contrast barium enema every five years
    • colonoscopy every 10 years

  • People with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age and be screened more often:

    • strong family history of colorectal cancer or adenomatous polyps in a first-degree relative, in a parent or sibling before the age of 50 or in two first-degree relatives of any age

    • family with hereditary colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC)

    • personal history of colorectal cancer or adenomatous polyps

    • personal history of chronic inflammatory bowel disease

Diagnostic procedures for colorectal cancer:

In addition to a complete medical history and physical examination, diagnostic procedures for colorectal cancer may include the following:

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 to other parts of the body. This is called staging, and is an important step toward planning a treatment program. The National Cancer Institute defines the following stages for colorectal cancer:

Stage 0 (Cancer in Situ) The cancer is found in the innermost lining of the colon.
Stage I (also called Dukes’ A colon cancer) The cancer has spread beyond the innermost lining of the colon to the second and third layers and the inside wall of the colon. The cancer has not spread to the outer wall of the colon or outside of the colon.
Stage II (also called Dukes’ B colon cancer) The cancer has spread outside the colon 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 physician based on:

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

Internal radiation involves giving a higher dose of radiation in a shorter time span than with external radiation. Some internal radiation treatments stay in the body temporarily. Other internal treatments stay in the body permanently, through the radioactive substance looses its radiation within a short period of time. In some cases, both internal and external radiation therapies are used.

Stanford Medicine Resources:

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