How do chemotherapy drugs work?

Chemotherapy drugs work by stopping cancer cells dividing and growing. Different drugs affect the cancer cells in different ways. When a combination of drugs is used, each drug is chosen for its different effects.

Most chemotherapy drugs are carried in the blood. This means they can reach cancer cells anywhere in the body. But chemotherapy can be given in different ways. The way you have chemotherapy depends on:

Chemotherapy drugs also affect some of the healthy cells in your body. These healthy cells can usually recover from damage caused by chemotherapy. But cancer cells cannot recover, and they eventually die.

Side effects of chemotherapy

Because chemotherapy drugs can affect some of the healthy cells in your body, this can cause side effects. Most side effects will go away after treatment finishes.

Healthy cells in certain parts of the body are more sensitive to chemotherapy drugs. For example, this includes cells in the bone marrow (which makes blood cells) and the digestive system.

This is why certain side effects are more common, such as being at risk of infection or feeling sick. We have more information about the side effects of chemotherapy and how they can be reduced and managed.

Chemotherapy

This video provides a brief overview of chemotherapy treatment, how it can be given, how it works and possible side effects.

We have videos about other treatment types

Chemotherapy

This video provides a brief overview of chemotherapy treatment, how it can be given, how it works and possible side effects.

We have videos about other treatment types

Monitoring the effects on the cancer

During treatment, your cancer doctor may want to find out how the cancer is responding to the chemotherapy drugs. This can be done in different ways:

  • If your doctor can see or feel the cancer, they will be able to tell if it is responding to chemotherapy by doing a physical examination.
  • If the cancer can be seen on a scan, you may have another scan after a few cycles of chemotherapy to see if the cancer is getting smaller. If you are having chemotherapy to reduce the risk of cancer coming back after surgery (adjuvant chemotherapy), you will not usually need scans to check if it is working.
  • With some cancers, blood tests can be used to check if treatment is working. These cancers release proteins into the blood (called tumour markers) that can be measured with a blood test. If the tumour markers are reducing, it usually means the chemotherapy is working.

If results show the cancer has not responded well enough, your doctor may decide to change your treatment to different chemotherapy drugs.

Back to Chemotherapy explained

What is chemotherapy?

Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. It can be given alone or with other treatments.

When is chemotherapy used?

Chemotherapy is used to kill cancer cells in the body. Your doctor will explain if chemotherapy is advised for you.