Chemotherapy drugs are medicine you receive to kill cancer cells. There are different types of chemo drugs that work in different ways. However, all chemotherapy drugs kill fast-growing cells, like cancer cells. Chemotherapy causes side effects because these medicines can kill other fast-growing cells, too, like cells in your skin and digestive tract.
Chemotherapy drugs are the medicines used during chemotherapy, or “chemo.” Chemotherapy is one of the most common and effective cancer treatments available. It destroys fast-growing cells, like cancer cells, and prevents them from multiplying.
Cells — including cancer cells and healthy cells — reproduce during a process called the cell cycle. During the cycle, a cell copies its genetic material (DNA) and divides to form new cells. Healthy cells reproduce when needed and die when they’re no longer useful (apoptosis). Cancer cells, on the other hand, don’t die. Instead, they multiply out of control and form tumors that can damage healthy tissue.
Chemotherapy drugs interfere with the cell cycle, killing cancer cells and preventing them from making more cancer cells. Various chemotherapy drugs use different methods to disrupt the cell cycle and fight cancer.
Chemotherapy drugs are primarily used to treat cancer. Cancer specialists called medical oncologists often prescribe chemotherapy drugs, in addition to other cancer treatments — like surgery, radiation therapy, immunotherapy or targeted therapy — to fight cancer.
Chemotherapy drugs may be used to treat conditions other than cancer, including:
Chemotherapy, surgery and radiation are the three most common cancer treatments. According to the Centers for Disease Control and Prevention (CDC), about 650,000 people with cancer receive chemotherapy in an outpatient cancer treatment setting in the U.S. each year.
Chemotherapy drugs are grouped based on their composition (what they’re made of) and how they destroy cancer cells. Some types of chemotherapy drugs work most effectively during specific phases of the cell cycle, while others kill cancer cells at all phases.
Your oncologist will consider the best timing to administer a chemotherapy drug and the optimal dosage when they plan your treatment.
You may receive one type of chemotherapy drug or a combination of drugs. This is called combination chemotherapy. Using more than one type of chemotherapy drug can increase treatment effectiveness, as different drug types target cancer cells differently. Also, using drugs in combination can reduce the likelihood of your body becoming resistant to a specific drug. Once you develop a resistance, the drug may no longer work as a cancer treatment.
What they do: Alkylating agents damage cell DNA to prevent cancer cells from dividing. Nitrosoureas are a particular type of alkylating agent. Unlike other alkylating agents, nitrosoureas can travel into your brain and kill cancer cells there. Nitrosoureas are used to treat some brain tumors.
Selected alkylating agents include:
Selected nitrosoureas include:
What they do: Antimetabolites prevent cancer cells from making the genetic material they need to create new cells.
Selected antimetabolites include:
What they do: Topoisomerase inhibitors prevent an enzyme called topoisomerase from allowing DNA to copy itself. Stopping this enzyme prevents cancer cells from multiplying and can also damage the cell DNA.
Selected topoisomerase inhibitors include:
What they do: Mitotic inhibitors are also called plant alkaloids because they’re made of the same material plants use to protect against predators. These drugs work by interfering with a cancer cell’s ability to divide and make new cells, a process called mitosis.
Selected mitotic inhibitors include:
What they do: Antitumor antibiotics prevent the DNA inside cancer cells from copying itself. Sometimes, they damage the cell’s DNA. Anthracyclines are a specific type of antitumor antibiotic.
Selected anthracyclines include:
Other antitumor antibiotics include:
Not all chemotherapy drugs fit into the main categories. Other common chemo drugs include:
What they do: Corticosteroids aren’t typically considered chemotherapy treatments. Healthcare providers prescribe them for a variety of conditions. Still, many people taking chemotherapy drugs also take corticosteroids to help manage side effects. These drugs can also kill cancer cells and prevent them from dividing.
Selected corticosteroids used during chemotherapy include:
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The most commonly prescribed chemotherapy medications are alkylating agents. They were also the first class of chemotherapy drugs developed. Still, other chemotherapy drugs or drug combinations may be more common depending on the type of cancer and how advanced it is (its stage).
Chemotherapy drugs have improved the outlook of many people with cancer. Cancers that were once considered deadly are now treatable. Many people are living longer, fuller lives thanks to chemotherapy drugs. Depending on your cancer diagnosis, chemotherapy drugs can:
Chemotherapy drugs target cells that divide and reproduce rapidly. This means they harm cancer cells but also other fast-growing cells that aren’t cancer. The cells in your skin, hair follicles, mouth and digestive tract and blood-forming cells in your bone marrow are all fast-growing cells that chemotherapy drugs can damage. The damage can cause side effects, including:
Your risk of side effects depends on the drugs you’re receiving for chemo. Ask your healthcare provider what side effects are most common with the drugs you’re taking.
Your outlook depends on various factors, including your overall health, the type of cancer, its stage and the treatments you’re receiving. Your outlook also depends on your treatment goals. For example, you may receive chemotherapy drugs as the first-line treatment to completely eliminate your cancer. You may receive it to shrink a tumor before surgery or to kill cancer cells that couldn’t be removed during surgery. You may receive chemotherapy to ease symptoms.
Ask your healthcare provider about your outlook based on your specific treatment goals.
Contact your oncologist if you’re experiencing unpleasant side effects during chemotherapy. They can suggest ways to manage side effects. In some cases, they may prescribe medicines to help lessen side effects. Depending on your situation, your oncologist may need to adjust your dosage and treatment schedule or try new medicines to treat your cancer.
The best chemotherapy drug is the one that’s proven to work best for your type of cancer. In some instances, the best chemotherapy drug isn’t a single drug but a combination that often works to treat a specific cancer type at a particular stage. In other instances, the best chemotherapy drug may be the one that works best alongside other treatments, like surgery or radiation therapy.
Ask your oncologist about the chemotherapy drugs you’re receiving and their record of success in treating your cancer type.
A note from Cleveland Clinic
Chemotherapy drugs are essential in the fight against cancer. Depending on your cancer, they can eliminate cancer cells entirely, prolong your life and improve your quality of life. They’re useful as a primary treatment or can complement other treatments you receive. Ask your oncologist about the benefits and potential side effects of the chemotherapy drugs you take. Help treatments work effectively by taking care not to miss any chemo appointments.
Last reviewed by a Cleveland Clinic medical professional on 10/20/2022.
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