What is chemotherapy?
Chemotherapy is a general term for treatments that use chemical agents (drugs) to kill cancer cells. Many different kinds of drugs are used, either alone or in combination, to treat different cancers. The specific drug or combination used is chosen to best combat the type and extent of cancer present.
Why are chemotherapy drugs given?
Chemotherapy drugs are given for several reasons:
- To treat cancers that respond well to chemotherapy
- To decrease the size of tumors for easier and safer removal by surgery
- To enhance the cancer-killing effectiveness of other treatments, such as radiation therapy
- In higher dosages, to overcome the resistance of cancer cells
- To control the cancer and enhance the patient’s quality of life
How does chemotherapy work?
Healthy normal cells in the body grow and divide in an orderly manner to replace old or damaged cells. Cancer cells have lost that capacity and divide out of control. Chemotherapy drugs work by interfering with the ability of cancer cells to divide and reproduce themselves. Chemotherapy can be delivered by the bloodstream to reach cancer cells all over the body, or it can be administered directly to specific cancer sites.
Each class of chemotherapy drugs damage cells in different ways:
- Prevent the copying of cellular components needed to divide
- Replace or eliminate essential enzymes or nutrients the cells needed to survive
- Trigger cells to self-destruct
Each chemotherapy drug works in a different way to prevent cells from growing. Often a combination of drugs will be used, with each drug attacking the cancer cells in a different way. This decreases the possibility that cancer cells will survive, become resistant and continue to grow.
How are chemotherapy drugs given?
Chemotherapy is given in different ways depending on the cancer type and the drugs used.
Methods of giving chemotherapy drugs include:
- Intravenously (IV) – injected into a vein
- Intrathecally (IT) – injected into the spinal canal during a lumbar puncture
- Intramuscular (IM) – injected into a muscle
- Intraperitoneal (IP) – injected into the abdominal cavity
- Intracavitary (IC) – injected into a body cavity
- Subcutaneous (sub.q.) – injected just under the skin
- Oral (PO) – as a pill or a liquid to be swallowed
How are chemotherapy drugs chosen for treatment?
For some types of cancer, the treatment plan is well established, through many years of research and experience. For other cancers, clinical research is in progress to find the most effective treatment, with the fewest number of side effects.
Why are there side effects from chemotherapy drugs?
Chemotherapy drugs target rapidly dividing cells, including normal ones. When normal cells are damaged, it can cause side effects. But normal cells can repair the damage or be replaced by other healthy cells, which is why side effects are usually temporary.
Factors influencing side effects include:
- The specific chemotherapy drug
- The dose of the drug
- The health of the patient
Despite monitoring the effects of chemotherapy very closely, some long-term effects can occur, sometimes years after therapy is completed. Therefore, it is important that every patient be followed throughout his or her life by a physician who is aware of the late effects of treatment.