Feb. 21–Feb. 28, 2005 Listen to the message

What is Cancer and How Do Cancer Therapies Work?

What is Cancer?

Cancer is a group of diseases in which unusual or abnormal cells in a part of the body begin to grow out of control. Many people think of cancer as a single disease, but this is not correct. There are over 300 different kinds of cancers grouped in to 15-20 large categories based on the location of the cancer. These are the ones we read and hear about, such as lung cancer, breast cancer, colorectal cancer, or leukemia. But did you know there are two major types of lung cancer and four major types of adult leukemia? Each of these disease types is a different cancer requiring specific treatments.

Normal cells of the body grow and divide in a very organized way. In adults, cells divide to replace damaged or worn-out cells. This process, called cell replication, is controlled by the body so that the number of cells dividing equals the number of damaged or worn out cells that need to be replaced. The body doesn’t make new cells when it doesn’t need them.

Cancer begins when cells in a certain part of the body, such as the colon or breast, begin to grow out of control. These cells do not stop growing or dividing. Over time, they may spread to other parts of the body by traveling through the blood stream or lymph system. This process of spread is called metastasis. Cancer cells that start in the colon grow and spread differently than cancer cells that start in the breast, so different treatments are needed to control or cure these very different cancers. Surgery, radiation therapy, chemotherapy, biotherapy, or a combination of any of these, may be used to try to stop the uncontrolled growth.

What Is Chemotherapy and How Does It Work?

Chemotherapy is the use of medicines that have been chosen because they interfere with growing and dividing cancer cells. Chemotherapy drugs travel through the body, so they can affect cancer cells in different parts of the body at the same time. A variety of chemotherapy drugs have been discovered that work on different types of cancer. Because many cancers are made up of a mixture of cells growing at different rates, patients often receive a combination of drugs instead of just one agent.

The most common way that people with cancer receive chemotherapy is an infusion or injection into the blood stream (called an intravenous infusion or I.V.). There are many other ways patients may receive chemotherapy, including swallowing pills, or getting injections into a muscle.

Why Does Chemotherapy Cause Side Effects?

Chemotherapy drugs are designed to kill cells that are dividing and growing, such as cancer cells. But your body has many normal cells that are also dividing and growing, and these can be affected by the chemotherapy as well. Different chemotherapy drugs cause different side effects, because they damage or kill different normal cells. Nausea and vomiting, a lower ability to fight infection, hair loss, and tiredness are all common side effects of chemotherapy.

What Is Radiation Therapy and How Does It Work?

Radiation therapy is the use of certain types of energy (called ionizing radiation) that are carried by waves or streams of particles into a cancer cell. The radiation kills the genetic material inside the cancer cell. This genetic material is critical to helping a cell grow and divide, so damage from radiation causes the cell to die. There are different types of radiation that are used, depending on the location, size, and type of cancer being treated. About half of all patients receive some type of radiation as part of their treatment for cancer.

Why Does Radiation Therapy Cause Side Effects?

Unlike chemotherapy, radiation therapy does not affect other cells throughout the body, only the cells closest to the area of radiation. The type of radiation therapy a person with cancer receives is very carefully selected to do as much damage as possible to the tumor, while doing as little damage as possible to the surrounding normal cells. But some normal cells are also damaged, although they usually recover from the radiation therapy and over time will begin to function normally again. Some common side effects are skin damage in the area of radiation; mouth sores and dryness in patients receiving radiation for head and neck cancer; nausea, vomiting, and diarrhea in patients receiving radiation to the stomach or pelvis.

What is Biotherapy and How Does It Work?

Our body has a natural system in place that fights infection and destroys unusual or damaged cells, called the immune system. Scientists think that certain cancers grow when our immune system is not strong enough to kill the unusual cells. Biotherapy is the use of the same substances our immune system makes, but in much larger amounts, to control cancer or to help relieve some side effects of chemotherapy. Biotherapy may be used by itself or in combination with chemotherapy or radiation therapy.

Why Does Biotherapy Cause Side Effects?

Because biotherapy is the use of large amounts of substances our immune system makes, it causes our body to experience the same physical symptoms we would have if we were fighting an infection (for example, the flu). The most common side effects of biotherapy are tiredness and fever.

The Good News About These Cancer Treatments and Their Side Effects

Treatments for cancer are not only increasing survival, but as improvements in the therapies are discovered, they are causing fewer side effects. Also, even if a treatment does cause side effects, there are many new medicines available to help manage those side effects so they are less of a problem. For example, there are very effective medicines available to control nausea and vomiting, one of the common side effects of treatment that many people are concerned about. Often patients no longer experience the severe bouts of nausea and vomiting that people even 10 to 15 years ago had to endure, because of new anti-nausea drugs that are now available.

As a cancer patient or someone who is caring for a cancer patient, one of the best things you can do is to learn all about the treatments and side effects for the particular type of cancer you are dealing with. Knowing what to expect and following the suggestions for preventing or decreasing side effects will make the whole cancer treatment process more manageable for you. For more specific information, both the National Cancer Institute and the American Cancer Society have excellent web sites (listed below). Just type in the treatment you are interested in into the search box and both web sites will give you very helpful information about the treatment, its side effects and what you can do to manage them.

www.cancer.gov (National Cancer Institute)
www.cancer.org (American Cancer Society)