Colorectal cancer

What is colorectal cancer?

Colorectal cancer is a malignant tumor of the colon or the rectum. Of the cancers affecting the large intestine, approximately 70 percent develop in the colon and 30 percent in the rectum. Roughly 95 percent of colorectal cancers are adenocarcinomas, cancers of the glandular cells that line the inside of the colon and rectum. Colorectal cancers develop slowly over a period of several years, starting with precancerous changes in the mucosal lining of the colon or rectum, and can grow through some or all of the tissue layers in the intestinal wall.

How many people get colorectal cancer?

Together, cancers of the colon and rectum are among the most common cancers in the United States. This year, it is estimated that there will be about 112,340 new cases of colon cancer and 41,420 new cases of rectal cancer, together causing about 52,180 deaths. They occur in both men and women and are most often found among people who are over the age of 50.

What causes colorectal cancer?

Although the exact cause of colorectal cancer is not known, there are certain risk factors for the disease, some of which are described below.

Family History

People with a family history suggesting these or other colorectal cancer syndromes should talk to their doctors about how often to have screening tests. This is because relatives of people who have had colorectal cancer are at increased risk of developing the disease themselves.

Some families may have a colorectal cancer syndrome such as hereditary nonpolyposis colorectal cancer (HNPCC) or familial adenomatous polyposis (FAP). In HNPCC, the onset of cancer tends to occur in people at a younger age and is not usually preceded by the presence of many polyps in the colon and rectum. Conversely, in FAP, cancer develops at a later age and affected persons typically develop hundreds of colorectal polyps—some of which will inevitably develop into cancer.

Ethnicity

Recent research has found an inherited tendency to develop colorectal cancer among some Jews of Eastern European descent, but the risk appears to be relatively small—much less than that caused by FAP or HNPCC.

Personal History of Colorectal Cancer

Even when a colorectal cancer has been completely removed, new cancers may develop in other areas of the colon and rectum.

Personal History of Polyps

Some types of polyps do not increase the risk of colorectal cancer. Other types, such as adenomatous polyps, do increase the risk of colorectal cancer, especially if they are large or there are many of them.

Personal History of Inflammatory Bowel Disease

This condition is also called ulcerative colitis or Crohn’s colitis. The colon is inflamed over a long period of time and may have ulcers in its lining. This increases the risk of colon cancer. People with this condition should start being screened for colorectal cancer at a young age and have the tests frequently.

Age

About nine out of 10 people with colorectal cancer are 50 years of age or older.

Diet Mainly From Animal Sources

A diet made up mostly of foods from animal sources can increase the risk of colorectal cancer. Many fruits and vegetables contain substances that interfere with the process of cancer formation. The American Cancer Society recommends eating at least five servings of fruits and vegetables every day, as well as servings of other foods from plant sources such as breads, cereals, grain products, rice, pasta or beans.

Lack of Exercise

Being active—even to a moderate degree—can lower the risk of colorectal cancer.

Obesity

Being very overweight increases a person’s colorectal cancer risk. Having excess fat in the waist area increases this risk more than having the same amount of fat in the thighs or hips.

Smoking

Most people know that smoking causes lung cancer but recent studies show that smokers are also 30 percent to 40 percent more likely than nonsmokers to die of colorectal cancer.

What are the symptoms of colorectal cancer?

Some symptoms of colorectal cancer include:

• A change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
• Still feeling the need to have a bowel movement even after you've just had one
• Bleeding from the rectum or blood in the stool
• Cramping or steady stomach pain

How is colorectal cancer diagnosed?

Screening tests are used to look for disease in people who do not have any symptoms. In many cases, these tests can find colorectal cancers at an early stage and greatly improve the chances of successful treatment. There are several test used to screen for colorectal cancer, some of which are described below.

Digital Rectal Exam (DRE)

The doctor or health care provider inserts a gloved finger into the rectum to feel for anything abnormal. Although DRE is often included as part of a routine physical exam, it is not recommended as a stand-alone test for finding colorectal cancer.

Fecal Occult Blood Test (FOBT)

The FOBT is used to test for traces of hidden (occult) blood in the stool. People having this test will receive a kit with instructions that explain how to take a stool sample at home. The kit is then sent to a lab for testing. If the test is positive, further tests are usually necessary to pinpoint the exact cause of the bleeding.

Sigmoidoscopy

A sigmoidoscopy involves placing a slender lighted tube (sigmoidoscope) in the rectum. This allows the doctor to look at the inside of the rectum and part of the colon for cancer or polyps. Because the tube is about two feet long, the doctor is only able to see about half of the colon.

Colonoscopy

The colonoscope is a long version of the sigmoidoscope. It allows the doctor to see the entire colon. If a polyp is found, the doctor may remove it. If anything else looks abnormal, a biopsy might be done. To do this, a small piece of tissue is taken out through the colonoscope, then sent to the lab to see if cancer cells are present.

Barium Enema With Air Contrast

A chalky substance is used to partly fill and open up the colon. Air is then inserted to cause the colon to expand, which allows good X-ray films to be taken.

Because there are several different screening tests available for finding colorectal cancer early, the American Cancer Society recommends that beginning at age 50, both men and women should follow one of these five screening options:

• Yearly fecal occult blood test
• Flexible sigmoidoscopy every five years
• Yearly fecal occult blood test plus sigmoidoscopy every five years
• Double-contrast barium enema every five years
• Colonoscopy every 10 years

People with certain risk factors should begin screening earlier or have screening more often.

How is colorectal cancer staged?

Staging is the process of finding out how far the cancer has spread. It is very important because, to a large extent, treatment and outlook for recovery depend on the stage of the cancer. In general, the lower the number, the less the cancer has spread.

Is colorectal cancer fatal?

The one- and five-year survival rates for colorectal cancers are 80 percent and 61 percent, respectively, and 54 percent of patients survive for 10 years. Prognosis improves when the cancer is diagnosed at an early, localized stage, with a five-year relative survival rate of 90 percent. However, only 37 percent of colorectal cancers are discovered at that stage. The five-year relative survival rate for a patient with regional and distant metastatic disease is 65 percent and 8 percent, respectively.

How is colorectal cancer treated?

Surgery is the main treatment for most stages of colorectal cancer and, for cancers that have not spread, it can be curative. Surgical treatment is commonly combined with chemotherapy and/or radiation therapy. Advances in the treatment of colorectal cancer include using immunotherapy to stimulate or enhance the immune system’s recognition and elimination of cancer cells.

Below are additional resources that may be helpful to you.