About immunotherapy

What is immunotherapy?

Immunotherapy is a treatment that uses the body’s own immune system to fight cancer. There are several different types of immunotherapy.

Checkpoint inhibitors help the immune system to recognise and attack cancer cells. Examples include pembrolizumab, nivolumab, ipilimumab, atezolizumab, durvalumab and avelumab. New checkpoint inhibitor drugs may become available in the future.

Other types of immunotherapy stimulate the immune system to help it work better against cancer. These include immune stimulants, chimeric antigen receptor (CAR) T-cell therapy and monoclonal antibodies.

Immunotherapy may be used on its own or with other cancer treatments. A combined immunotherapy drug is also now available (for people with advanced melanoma). Immunotherapy can be given as the first treatment, or when the cancer has not responded to or has come back after other treatments.

How the immune system works

The immune system is a network of cells, chemicals, tissues and organs. It includes the lymph nodes, spleen, thymus, tonsils and bone marrow, as well as white blood cells known as lymphocytes.

This network tries to protect the body from infections and from abnormal cells such as cancer cells. When a germ enters the body, or when a cell becomes abnormal, the immune system usually recognises and then attacks the germ or cell so that it does not harm the body. This is called an immune response. The immune system can remember every germ or abnormal cell it has attacked so it can easily recognise them if they appear in the body again.

Immunotherapy and the immune system

To keep you healthy, the immune system needs to be carefully balanced. If it is too weak, you will be prone to infection and disease. If it is too active, it can start to attack normal cells and lead to autoimmune diseases such as rheumatoid arthritis and lupus.

Tipping the balance

Cancers find ways to disrupt the balance of the immune system so that it does not see cancer cells as abnormal. Immunotherapy manipulates the immune system to restore the balance and allow it to recognise and attack the cancer.

Immune system side effects

If immunotherapy makes the immune system overactive, it may affect normal cells as well as cancer cells. This means you can get side effects anywhere in the body.

After treatment

The immune system has a “memory”, so immunotherapy sometimes keeps working long after treatment finishes. This means side effects can appear months or even years after treatment, and some can be long term.

Cancer and the immune system

Cancer starts when abnormal cells begin growing out of control. The immune system usually stops new cancers from developing because it recognises abnormal cells and destroys them. When the body’s immune response is not able to kill all the abnormal cells, these cells can develop into cancer.

The immune system has natural mechanisms (“checkpoints”) that prevent it from becoming too strong and attacking healthy cells and tissue. Some cancers take over these checkpoints and use them to prevent the immune system from attacking the cancer cells. 

Cancers may also change over time (mutate), which helps them to “hide” from the immune system. This is why treating cancer isn’t as simple as boosting the immune system. Modern immunotherapy drugs try to help the immune system in very specific ways.

Some people with cancer wonder if they should try special diets or supplements to boost the immune system so it can fight the cancer. While having a healthy diet is always important, extreme diets are not proven to be effective and can be harmful. Talk to your doctors before starting any special diets or taking supplements during cancer treatment.

How cancer is treated

Because each cancer is unique, people may have different treatment plans, even if their cancer type is the same. The 3 most common cancer treatments are:

• surgery
• chemotherapy
• radiation therapy (also called radiotherapy).

Other, newer treatments used for some types of cancer include:

• immunotherapy
• targeted therapy
• hormone therapy.

Chemotherapy, targeted therapy, immunotherapy and hormone therapy are all drug therapies. They are known as systemic treatment because the drugs circulate throughout the body.

Cancer treatments may be used on their own or in combination. For example, you may have surgery to remove a tumour, followed by immunotherapy to stop the cancer returning. Doctors will recommend the best treatment for you based on the type and stage of the cancer, its genetic make-up, your age and your general health.