Chemotherapy Health Article

Definition

Chemotherapy, sometimes referred to as "chemo," is the treatment of cancer with anticancer drugs.

Purpose

The main purpose of chemotherapy is to kill cancer cells. It usually is used to treat patients with cancer that has spread from the place in the body where it originated (metastasized). Chemotherapy destroys cancer cells anywhere in the body. It even kills cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body.

Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. Chemotherapy may be given before surgery or radiation therapy to shrink the tumor (neoadjuvant therapy). When a cancer has been removed by surgery or treated with radiation therapy, chemotherapy may be used to keep the cancer from coming back (adjuvant therapy).

Once a remission is achieved, consolidation chemotherapy, also called intensification chemotherapy, is given to sustain a remission. Maintenance chemotherapy is chemotherapy given in lower doses as a treatment to prolong a remission in certain types of cancer. Chemotherapy also can ease the symptoms of cancer (palliative chemotherapy), helping some patients have a better quality of life.

Description

Chemotherapy for the treatment of cancer began in the 1940s with the use of nitrogen mustard. More than 100 chemotherapy drugs are now available to treat cancer, and many more are being tested for their ability to destroy cancer cells.

Most chemotherapy drugs interfere with the ability of cells to grow or multiply. Although these drugs affect all cells in the body, many useful treatments are most effective against rapidly growing cells. Cancer cells grow more quickly than most other body cells. Other cells that grow fast are cells of the bone marrow that produce blood cells, cells in the stomach and intestines, and cells of the hair follicles. Therefore, the most common side effects of chemotherapy are linked to the treatment's effects on other fast-growing cells.

Types of chemotherapy drugs

Chemotherapy drugs are classified according to how they work. The main types of chemotherapy drugs are:

• Alkylating drugs—kill cancer cells by directly attacking DNA, the genetic material of the genes. Cyclophosphamide is an alkylating drug.
• Antimetabolites—interfere with the production of DNA and keep cells from growing and multiplying. An example of an antimetabolite is 5-fluorouracil (5-FU).
• Antitumor antibiotics—made from natural substances such as fungi in the soil. They interfere with important cell functions, including production of DNA and cell proteins. Doxorubicin and bleomycin belong to this group of chemotherapy drugs.
• Plant alkaloids—prevent cells from dividing normally. Vinblastine and vincristine are plant alkaloids obtained from the periwinkle plant.
• Steroid hormones—slow the growth of some cancers that depend on hormones. For example, tamoxifen is used to treat breast cancers whose growth depends on the hormone estrogen.
• Topoisomerase inhibitors—interfere with the action of topoisomerase enzymes, the enzymes that control the part of DNA needed to multiply. Etoposide belongs to this group.

Biological therapy

Biological therapy, also called immunotherapy, consists of treatment with substances that boost the body's own immune system against cancer. The body usually produces these substances in small amounts to fight diseases. These substances can be made in the laboratory and given to patients to destroy cancer cells, change the way the body reacts to a tumor, or help the body repair or make new cells destroyed by chemotherapy.

Combination chemotherapy

Chemotherapy usually is given in addition to other cancer treatments, such as surgery and radiation therapy. When given with other treatments, it is called adjuvant chemotherapy. An oncologist decides on the specific chemotherapy drug or combination of drugs that will work best for each patient. The use of two or more drugs together—combination chemotherapy—often works better than using a single drug. Scientific studies of different drug combinations help doctors learn the combinations that work best for each type of cancer. For example, research in 2003 found that a combination of chemotherapy and gene therapy stopped breast cancer and its metastasis (spread to other organs or parts of the body).

Clinical trials

Some patients may be eligible to participate in clinical trials, research programs conducted with patients to evaluate a new drug, medical treatment, device, or combination of treatments. The purpose of clinical trials is to find new and improved methods of treating different diseases and special conditions. More information is available at the National Institutes of Health's clinical trials Web site, <www.clinicaltrials.gov> or by calling (888) FIND-NLM, (888) 346-3656 or (301) 594-5983. Another resource is the National Cancer Institute's Web site, <www.cancer.gov/clinicaltrials>.