Cancer chemotherapy is the use of drugs to kill cancer cells. Unlike radiation therapy and surgery, which are localized treatments, chemotherapy is a systemic treatment, meaning the drugs travel throughout the whole body. This means chemotherapy can reach cancer cells that may have metastasized to other areas.
Chemotherapy is used in 5 different ways:
Understanding how normal, healthy cells grow and divide is essential to understanding how chemotherapy works. All living things are composed of cells. Cells grow, divide, and die in a regulated fashion. The cell cycle is the process that normal and abnormal cells go through to grow and reproduce.
Five phases comprise the cell cycle:
Normal, healthy cells go through the cell cycle in a regulated manner—as some cells are dividing and creating new cells, other cells are dying. Abnormal cells divide and reproduce uncontrollably, creating a mass of cells known as a tumor.
The cell cycle is important to chemotherapy because chemotherapeutic drugs target and disrupt different phases of the cell cycle. Most chemotherapy drugs act on reproducing cells (not those in the G0 phase). Because cancer cells actively reproduce, they are primarily targeted by chemotherapeutic drugs. However, healthy cells reproduce as well, so they too are affected by chemotherapy. This is what causes side effects. When chemotherapy is given, the doctor must find a balance between destroying the cancer cells and sparing the normal cells.
Chemotherapy is given for the following reasons:
Chemotherapy is used to treat many different types of cancer. The type, location, and stage of the cancer as well as your general health will largely determine if chemotherapy is appropriate and which agents ought to be used. For example, adjuvant chemotherapy is considered standard treatment for breast, colon, and rectal cancers. Neoadjuvant chemotherapy has been used effectively in breast, bladder, esophageal, laryngeal, and locally advanced non-small cell lung cancers.
Brain tumors are more difficult to treat with chemotherapy because of the shielding effect of blood-brain barrier (BBB), the tumor's location inside the skull, and the lack of adequate lymphatic drainage.
Chemotherapeutic drugs are classified by their pharmacologic action and their interference with cellular reproduction. They are divided into cell cycle phase-specific and cell cycle phase-nonspecific.
Cell Cycle Phase-specific
Cell cycle phase-specific drugs act on cells undergoing division. Therefore they affect cells in phases G1, S, G2, or M, but not G0. Because these drugs exert their cytotoxic effects during the cell cycle, they are most effective against actively growing tumors. They are given in minimal concentrations using continuous dosing methods. Examples include the following:
Cell Cycle Phase-nonspecific
Cell cycle phase-nonspecific drugs act on cells either in dividing or resting states. Because these drugs are active in all phases of the cell cycle, they may be effective in large tumors that have fewer active cells. Cell cycle phase-nonspecific drugs are usually given as a single injection. Examples include the following:
Chemotherapy can be administered via several routes. The most common method is through an IV. Usually, a thin needle is inserted into a vein on the hand or lower arm at the onset of the treatment session and is removed at the conclusion.
Chemotherapy can also be delivered by IV through catheters, ports, and pumps. A catheter is a soft, thin, flexible tube that is placed in a large vein in the body. It remains in place as long as necessary. Sometimes the catheter is attached to a port, which is a small round plastic or metal disc placed under the skin. The port stays in place as long as necessary. A pump can be used to control how fast the drugs go into the catheter or port. An external pump remains outside the body, while an internal pump is surgically placed just under the skin.
Common IV delivery methods include:
Chemotherapy can also be delivered in methods other than IV. These include:
Because chemotherapy can kill healthy cells along with cancer cells, many side effects are associated with this form of treatment. The most common side effects occur in areas where healthy cells rapidly divide. These include:
You may experience no side effects or just a few. The kind of side effects and how severe they are will depend on the type and dose of chemotherapy and how your body reacts. Some of the more common side effects are described below.
Fatigue, feeling tired and lacking energy, is the most common symptom experienced by people receiving chemotherapy. Fatigue from chemotherapy feels different from the fatigue that you may experience from everyday life. Chemotherapy fatigue can appear suddenly. Some people have described it as a total lack of energy, feeling drained or wiped out. The fatigue can last days, weeks, or months, but it usually goes away gradually as your body responds to treatment.
There are some things you can do to help cope with fatigue:
Nausea and vomiting are common side effects of several chemotherapeutic agents. Chemotherapeutic drugs irritate the lining of the stomach and the first section of the small intestine (duodenum), which stimulates certain nerves that lead to the vomiting center of the brain.
Although everyone is different, certain drugs are more likely to cause vomiting than others.
|Melphalan (in high doses)||Plicamycin|
|Streptozocin||Methotrexate (in high doses)|
|Cytarabine (in high doses)||Carboplatin|
|Etoposide (in high doses)||Doxorubicin|
Many things can influence the likelihood and severity of nausea and vomiting:
There are some things that can be done to help control the nausea and vomiting associated with chemotherapy:
Antiemetics have been developed to help control the nausea and vomiting associated with chemotherapy, many of which can be extremely effective:
Talk with your doctor to see if one or a combination of these antiemetic medications is right for you.
Chemotherapeutic drugs can cause painful side effects as well. They can damage nerves, most often in the fingers and toes, which leads to burning, numbness, tingling, or shooting pain. Some drugs also cause mouth sores, head and muscle aches, and joint pain and stomach pain. Because not everyone who undergoes chemotherapy experiences pain, it is important to let your doctor know if you feel pain. Steps can be taken to relieve it. There are many different medications and methods to help control pain.
Pain is often measured on a scale from 0 to 10 (with 0 as no pain). Keep a journal to know the timing, location, and type of pain. Write down any steps taken and if it made the pain better or worse.
The goal of pain control is to prevent pain that can be prevented and to control pain that cannot be prevented. Talk with your doctor to determine what method or methods will work best for you.
Hair loss is a notorious side effect of chemotherapy, but not all chemotherapeutic drugs cause hair loss. Talk with your doctor to see if the regimen you are on may cause hair loss.
Hair loss usually occurs between 10 and 21 days after drug administration. It may happen suddenly and in large amounts or hair may fall out gradually. Hair loss is temporary and hair should grow back after treatment is stopped.
To care for the scalp and hair:
Although not life-threatening, hair loss can be very upsetting. Many people buy a wig or hairpiece, or use hats or scarves, to cover their head. If you buy a wig because of cancer treatment, it is a tax-deductible expense and may be covered in part by health insurance. Shop for these items before any hair falls out to get the best match.
One of the most common side effects of chemotherapy is bone marrow suppression, also known as myelosuppression. Bone marrow is the tissue inside of some bones, such as the sternum (breastbone), hip, femur (thigh), and humerus (upper arm), which produces white blood cells, red blood cells, and platelets. Because cells in the bone marrow tissue grow and divide rapidly, they are susceptible to the effects of chemotherapy.
Blood cell counts do not drop immediately after starting chemotherapy because the drugs do not kill cells already in the blood stream. Chemotherapeutic drugs, instead, prevent bone marrow from forming new blood cells. Each type of blood cell has an average life span, which has an impact on when each type of blood cell reaches its lowest levels, called the nadir. The average life spans are:
Blood normally has between 4,000 and 10,000 WBCs per cubic millimeter. When your white blood cell count falls, it is known as neutropenia. The main function of white blood cells is to help the body resist infection. Because the white blood cells play such an important role in your health, your doctor will monitor your white blood cell level carefully.
If your WBC count falls, you will not automatically get an infection. But, it is important to watch for signs and symptoms of a possible infection:
Naturally occurring hematopoietic growth factors stimulate the production of different types of blood cells. These growth factors can be produced in a laboratory and are available as drugs. The 2 growth factors that stimulate production of white blood cells are granulocyte-macrophage colony stimulating factor (GM-CSF) and granulocyte colony stimulating factor (G-CSF). They are frequently given the day after you start chemotherapy and for up to 2 weeks.
There are things you can do to decrease your risk of infection:
Report any signs of infection to your doctor immediately.
A low level of red blood cells is called anemia. Blood normally has between 4 and 6 million red blood cells per cubic millimeter. Red blood cells carry oxygen to all parts of your body. If your red blood cell count drops, you may experience the following:
If you are anemic, the following suggestions may help you feel less tired:
Erythropoietin is a naturally occurring growth factor that stimulates red blood cell production. The drug forms are called erythropoiesis-stimulating agents (ESAs). ESAs are usually given 3 times per week by injection under the skin until red blood cell counts rises.
A low platelet count is called thrombocytopenia. The normal range for platelet counts is between 150,000 and 450,000 per cubic millimeter. Platelets are the blood cells that help stop bleeding by making your blood clot. Signs that your platelet count is low include the following:
Very low platelet counts can lead to serious internal bleeding. If your platelet counts fall below a specific number, you may be given platelet transfusions. Oprelvekin, a platelet growth factor, can be given if you have severe thrombocytopenia.
Many chemotherapy drugs cause a decrease in or complete loss of appetite. Each person is different and there is no way to predict how chemotherapy will affect you. But appetite loss and weight loss can range from mild to severe and may lead to malnutrition. The decrease in appetite is usually temporary. Your appetite should return after chemotherapy has stopped, but it may take several weeks.
In those with certain types or advanced cancers that are resistant to treatment, cachexia is possible. Cachexia, or wasting, is a significant loss of weight and muscle mass, which can occur without loss of appetite or decreased intake of calories. Treating the cancer is the most effective way to overcome cachexia. Dietary changes or medications have little effect on regaining lost weight.
Because chemotherapy can alter your sensation of taste, the therapy can affect the way some foods taste and smell to you, adding to your poor appetite and weight loss. Your taste and smell should return to normal several weeks after chemotherapy has ended.
In order for your body to fight the cancer and cope with chemotherapy, it is important that you get proper nutrition. If you are experiencing loss of appetite, talk with your doctor—there are medications that can help.
There are some things you can do to boost nutrition:
Some chemotherapy drugs can affect your central nervous system. These side effects can occur soon after chemotherapy or years later:
Some chemotherapeutic drugs can cause sores and inflammation in the mouth, known as stomatitis. Changes in the throat (pharyngitis) or esophagus (esophagitis) can also occur. Mucositis is the term used to refer to inflammation of the lining of the mouth, throat, and esophagus.
There are some things you can do to help keep your mouth, gums, and throat healthy:
If you do experience mouth sores, try the following to help manage them:
Chemotherapy can cause reproductive and sexual problems. Whether or not you experience these changes will depend on a few factors:
Everyone responds to treatment differently. Side effects may or may not affect you. Don't feel embarrassed to talk with your doctor about your concerns regarding sexual and reproductive side effects.
Some reproductive and sexual changes a woman may experience include the following:
Men undergoing chemotherapy should use condoms because of the changes in or damage to sperm cells, which can create pregnancy or birth complications. Other reproductive and sexual changes a man may experience include the following:
Some side effects can lead to infertility in both men and women. If you and your partner are planning a family, talk to the doctor before you start treatment. There are resources and treatments available to preserve fertility while undergoing chemotherapy so you can have your family after. Some options may also be available for children or adolescents depending on their stage of development.
For details on the use of chemotherapy for specific cancers, see the following articles:
A guide to chemotherapy. American Cancer Society website. Available at: https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/chemotherapy.html. Accessed February 28, 2020.
Chemotherapy. National Cancer Institute website. Available at:
...(Click grey area to select URL)
Updated April 29, 2015. Accessed December 27, 2016.
Ettinger DE, Berger MJ, Barbour SB, et al. Antiemesis. Version 1.2015. In: National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology (NCCN Guidelines). NCCN 2015 April.
Hesketh PJ. Chemotherapy-induced nausea and vomiting. N Engl J Med. 2008 Jun 5;358(23):2482.
Toxicities of chemotherapeutic agents. EBSCO DynaMed Plus website. Available at: https://www.dynamed.com/topics/dmp~AN~T115935/Toxicities-of-chemotherapeutic-agents. Updated September 16, 2019. Accessed December 27, 2016.
Last reviewed December 2019 by Mohei Abouzied, MD
Last Updated: 11/26/2019