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The colon and rectum
Colorectal cancer begins in either the colon or the rectum. Both are part of the digestive tract, which is a series of tubes and organs that process the food we eat. Digestion begins in the stomach. From the stomach, partly digested food passes into the small intestine, the longest section of the digestive tract, which absorbs most of the nutrients. The food then continues into the large intestine (the colon), which is a muscular tube approximately 5 feet long. In the colon, the remaining water and nutrients are extracted from the food and the rest is stored as waste. The waste moves from the colon into the rectum, and then passes out of the body through the anus during a bowel movement. Cancer is similar in the colon and the rectum, so they often are discussed together.
Polyps and adenocarcinoma
Colorectal cancer does not happen overnight. It can take many years to develop, and it usually is preceded by changes in the lining of the colon or rectum that occur over several years. One of these changes is a growth of tissue into the center of the colon or rectum, called a polyp. Not all polyps develop into cancer, but some do. Removing a polyp early can prevent it from becoming cancer.
Ninety-five percent of colorectal cancers are of the particular kind called adenocarcinoma. These cancers begin in the lining of the colon or rectum and can grow either into the center of the colon or rectum, or outward through the wall. If the cancer is not treated, cancerous cells can break away into the circulatory system and travel to other parts of the body. When a cancer spreads in this way, it is said to have metastasized.
Risk factors
No one knows for sure what causes colorectal cancer, although there are a number of risk factors that may increase a person's chances of developing it. Sometimes people inherit colorectal conditions that increase their chances of developing cancer. Having certain types of polyps (particularly large and numerous ones) also increase the risk. People who already have had colon cancer are at greater risk of developing new cancers in other areas of the colon and rectum.
To reduce risk, experts recommend eating a diet high in fruits, vegetables, and whole grain foods. Similarly, regular exercise may help to prevent colorectal cancer.
What Happens When People Have Colorectal Cancer?
Signs and symptoms
The symptom that brought Darryl Strawberry to the doctor was gnawing pains in his abdomen. Another symptom a person might notice is a change in bowel habits, for example, diarrhea or constipation that lasts for more than a few days. Or a person might feel the need to have a bowel movement even after they have had one, or one might notice bleeding from the rectum or blood in the stool.
Diagnosis
Just because people have symptoms does not mean that they have colorectal cancer. But the only way to be sure is to consult a doctor. It also is possible to have colon or rectal cancer and not to have any symptoms at all. For this reason, tests to screen for colorectal cancer are recommended for people over 50, whose age puts them at greater risk for developing the disease.
Did You Know?
The American Cancer Society reports the number of cases of colon and rectal cancer in the U.S. for 1999 as follows:
- • 43,000 men and 51,700 women diagnosed with colon cancer
- • 19,400 men and 15,300 women diagnosed with rectal cancer
- • 9 out of every 10 people diagnosed with colorectal cancer are older than age 50
- • The number of people who die from colorectal cancer has been going down for the past 20 years
The simplest test is a digital rectal exam. The doctor inserts a gloved finger into the rectum to feel for anything that is not normal. People often are shy at the thought of such a test, but it is very effective in detecting certain kinds of cancers. Other tests use special instruments to examine parts of the colon. If the doctor finds anything unusual, he or she may remove a small amount of tissue for examination under the microscope (a biopsy) to see whether the tissue is cancerous or benign (harmless).
How Is Colorectal Cancer Treated?
If cancer is found, the next step is to do tests to see whether it has spread. Doctors use a system of numbers or letters to stage, or classify, the cancer. The lower the number or letter, the less the cancer has spread. A higher number, for example, stage IV, means a more serious stage of the disease. The three main types of treatment for colorectal cancer are surgery, radiation therapy, and chemotherapy:
- Surgery is the main treatment for both colon and rectal cancer. In some more advanced instances of rectal cancer, a person may need to have a colostomy. Colostomies usually are not needed in colon cancer.
- Radiation therapy uses high-energy radiation to kill cancer cells. It is used to kill small areas of cancer that might not have been removed during surgery.
- Chemotherapy refers to the use of anticancer drugs to kill cancer cells. The drugs may be given through a vein in the arm or as pills, which means that they can enter the bloodstream and can reach any area of the body where metastasized cancer cells may have traveled.
Can Colorectal Cancer Be Prevented?
Scientists do not know how to prevent colorectal cancer, but there are steps people can take to reduce their risk.
Screening
Because finding colorectal cancer early often means it can be cured, people age 50 and older should follow the screening guidelines established by the American Cancer Society. Younger people whose close relatives (mother, father, sister, or brother) have had colorectal cancer or physical conditions that increase the risk for colorectal cancer should begin screening earlier than age 50. Younger people who have had colorectal cancer already must be particularly careful to follow up with their doctors regularly to make sure the cancer does not return. Eating a healthy diet, getting plenty of exercise, and never smoking are other things people can do to decrease their risk.
Research
If detected and treated early, colorectal cancer can be cured. Researchers now are studying the use of natural or man-made chemicals to lower a person's risk of ever developing colorectal cancer. Another area of investigation is in the kinds of changes to DNA that people inherit or acquire during the lifespan that might cause the cells of the colon and rectum to become cancerous. Such studies could lead to new drugs and new therapies for correcting those problems. Researchers also are working to develop colorectal screening methods that are faster and more comfortable than the ones available now. Experimental treatments that enlist the body's own defenses in the fight against cancer also are being tested.
What Is It Like to Live with Colorectal Cancer?
Caught in the early stages, colorectal cancer is one of the most curable cancers. People recover from surgery and resume their normal lives. Many people feel shame about colorectal cancer, however, because it involves a part of the body they do not usually talk about. Moreover, people who have had permanent colostomies may feel different from everyone else. Everyone's reaction to cancer and to treatment is different. There is no single right way to handle it. Support groups can be particularly helpful for people who are living with this very curable form of cancer.
Sigmoidoscopy and Colonoscopy
Colorectal cancer is highly curable if it is caught early. Two tests can help to prevent or cure many cases of colon cancer.
The first is called sigmoidoscopy. In this test, the doctor uses a slender, lighted tube linked to a video camera to examine the rectum and lower part of the colon. This is where most cancers and polyps are found.
Another test is called colonoscopy. In this test, a long, thin, flexible tube linked to a video camera allows the doctor to examine the entire length of the colon. If polyps are found, they can be removed using a wire loop. Because polyps take 6 to 10 years to develop into cancers, removing them early can help prevent them from becoming cancerous.
