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What is immunotherapy?

Immunotherapy is a treatment that uses the body’s own immune system to fight cancer. There are several types of immunotherapy, and each works differently. The main type of immunotherapy for cancer uses drugs known as checkpoint inhibitors, which remove barriers that stop the immune system from finding and attacking cancer.

Immunotherapy may be used on its own or with other cancer treatments. It is most often given when cancer has not responded to or has come back after initial treatment. In some cases, it may be available as part of the first treatment plan.

Other types of immunotherapy stimulate the immune system to help it work better against cancer and include immune stimulants, CAR T-cell therapy and oncolytic virus therapy. A few have been approved to treat particular cancers, but most are still being tested in clinical trials. 

The immune system

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. Together, 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 process is known as 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. 

The role of 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 attack the cancer.
  • Immune side effects – if immunotherapy makes the immune system overactive, you can get side effects anywhere in the body.
  • After treatment – because the immune system has a 'memory', immunotherapy sometimes keeps working long after treatment finishes. This means side effects can also appear months or even years after treatment. 

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. In some cases, the body’s immune response is not able to kill all abnormal cells and they develop into cancer.

Cancer cells find ways to stop the immune system from destroying them – for example, by setting up barriers ('checkpoints') so the immune system can’t recognise them, or by changing over time (mutating) to avoid being found by 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 doctor before starting any special diets or supplements during cancer treatment. 

Some vaccines are not used to treat cancer, but can help prevent it. They do this by training the immune system to attack viruses that have been linked to certain cancers. It is important to check with your cancer specialist before having vaccinations, including for flu or COVID-19, if you have had immunotherapy.


Choosing immunotherapy

Immunotherapy using checkpoint inhibitors has worked well for some people, but it does not help everyone. It is available for some types of cancer including bladder, head and neck, Hodgkin and non-Hodgkin lymphoma, kidney, liver, lung, melanoma and Merkel cell carcinoma.

So far, most people who have been treated with checkpoint inhibitors have had advanced cancer. For some cancer types, immunotherapy is starting to become available for earlier-stage cancers.

Even if immunotherapy is recommended, it is difficult to predict whether it will work as the rate of success varies greatly. To work out if immunotherapy is an option for you, your doctor will consider:

  • the type and stage of cancer
  • your treatment history
  • your future treatment options
  • your overall health.

To access immunotherapy, talk to your cancer specialist. Ask if any checkpoint inhibitors would be a suitable treatment for you and whether they are reimbursed through the PBS for your type of cancer.

How long will it take to work?

Like most other cancer treatments, immunotherapy usually takes a while to work, so you and your family may experience anxiety waiting to see whether you’ll respond to the treatment. If it does work, you may worry about how long immunotherapy will control the cancer or whether the cancer will come back. 

Some media reports have claimed that checkpoint inhibitors are 'miracle drugs' that can cure cancer. This means that people often have very high expectations when starting immunotherapy, or they may be confused and upset if they aren’t offered it.

If immunotherapy doesn’t work or stops working, ask your cancer specialist about your other treatment options. You may be able to try another type of checkpoint inhibitor or join a clinical trial.

It is important to tell your cancer specialist if you have an autoimmune disease or have had an organ transplant, as this may affect the outcome of immunotherapy.

How much will it cost?

Checkpoint inhibitors are expensive (often several thousand dollars per dose), but the Australian Government covers most of this cost for some drugs for some types of cancer through the Pharmaceutical Benefits Scheme (PBS). Other cancer types and new drugs may be added to the PBS in the future.

If the drug is not on the PBS, you may be able to get checkpoint inhibitors through clinical trials or, sometimes, through a compassionate access program or cost-share program offered by the pharmaceutical company. Some people choose to pay the entire cost themselves, but this can involve major financial decisions.

Before deciding to pay for any cancer treatment, it is important to fully understand the total cost, as well as the likely rates of success and the possible risks and benefits of the treatment. Take the time to discuss these questions with your cancer specialist and your family or close friends. 


How it is given

Checkpoint inhibitors are usually prescribed by a medical oncologist or haematologist, and are given as a liquid through a drip inserted into a vein. Sometimes two or more drugs may be given together. You will usually have immunotherapy as an outpatient and in repeating cycles, with rest periods of 2–6 weeks in between.

How often and how long you have the treatment depends on the type of cancer and how advanced it is, the type of checkpoint inhibitor, how the cancer responds to the treatment and what side effects you experience. Many people stay on immunotherapy for up to two years. 

Checkpoint inhibitors can take weeks or months to start working, depending on how your immune system and the cancer respond. Most cancers have treatment protocols that set out which drugs to have, how much and how often. Your specialist may need to tailor the protocols to your individual situation.

Like many other cancer treatments, immunotherapy drugs are often not safe to use if you are pregnant or breastfeeding. Ask your doctor for advice about contraception. 

Side effects

Like all treatments, checkpoint inhibitors can cause side effects. These are sometimes called immune-related adverse effects (IRAEs). Immunotherapy side effects need to be managed differently to the side effects of other cancer treatments.

You may have side effects within days of starting treatment, but more commonly they occur several weeks or months later. In some rare cases, new side effects can appear months after finishing treatment.

Most people have mild side effects, but they are likely to be more severe if you are having higher doses or a combination of immunotherapy drugs, or if you are having immunotherapy with other cancer treatments.

Checkpoint inhibitors trigger an immune response that can lead to redness, swelling or pain (inflammation) anywhere in the body. Side effects will depend on which part of the body becomes inflamed. 

Common side effects include:

  • Fatigue tiredness that does not go away with rest, caused by inflammation throughout your body.
  • Dry eyes – could be inflammation of the eyes or tear glands.
  • Changes in weight and body temperature – could be inflammation causing the thyroid to work too fast (hyperthyroidism, leading to weight loss and feeling warm) or too slow (hypothyroidism, leading to weight gain and feeling cold).
  • Skin rash and itching – could be dermatitis, which makes skin red, bumpy and itchy.
  • Diarrhoea, abdominal pain and bloating – could be inflammation of the bowel (colitis).
  • Pain in the joints – could be inflammation of the joints (arthralgia), especially if you already have arthritis or a similar condition.

Rare side effects include:

  • Headache or blurred vision – could be inflammation of the pituitary gland (hypophysitis) or the membranes around the brain and spinal cord (meningitis).
  • Breathlessness, coughing, fainting or chest pain – could be a lung or heart problem, which is rare but serious.
  • Yellowing of the eyes, severe abdominal pain and dark urine – could be inflammation of the liver (hepatitis).
  • Excessive thirst or urination – could be inflammation of the pancreas affecting the production of insulin.
  • Reduced urination or blood in the urine – could indicate problems in the kidneys, which is very rare but serious.
  • Muscle pain – could be inflammation of the muscles (myositis).
  • Confusion or seizures – could be nerve problems, which is very rare but serious.

Managing side effects

Because immunotherapy works differently from other cancer treatments, it’s important to work closely with your treatment team to monitor any side effects and how the cancer responds. Before starting immunotherapy, discuss the potential side effects with your cancer specialist. Ask which side effects to watch out for or report, who to report them to, and who to contact after hours. 

Before treatment begins, you will usually have some tests to check that you are well enough to have immunotherapy. Throughout treatment, the team will regularly test your blood and ask you questions to check for early signs of side effects. New side effects can appear months after having immunotherapy, so ask your cancer specialist how long you need to keep watching for side effects. 

Reporting side effects

Side effects can be better managed if reported early, so it is important to let your cancer care team know about new or worsening symptoms, even if they seem minor or you’re not sure if they are related to your treatment. If left untreated, side effects can become serious and may even be life-threatening.

Sometimes it can be tricky to know whether your symptoms are related to the cancer or the treatment. Make sure to discuss this with your cancer care team. Because immunotherapy is a newer cancer treatment, GPs and other health professionals may not yet be familiar with the side effects.

Your team may give you a card with information about your immunotherapy treatment and potential side effects. You can show this card to other health professionals you see and ask them to consult with your cancer specialist. Do not start any new medicines, including anti-inflammatory steroids, herbal therapies or over-the-counter medicines, until your cancer specialist has been consulted.

If you become unwell, even years later, it is important to tell any health professionals you see that you have had immunotherapy.

Treating side effects

Side effects are graded on a scale of 1–4. Your doctor will tell you how to manage mild to moderate side effects (grades 1–2). Moderate to severe side effects (grades 2–4) are often treated with steroid tablets, such as prednisolone. In some cases of severe side effects (grades 3–4), people may need to stay in hospital and/or have intravenous steroids or other medicines, and immunotherapy may be stopped until the side effects are better controlled.

If side effects become too severe, you may have to stop immunotherapy permanently. In this case, the immunotherapy that you have already received may have 'trained' your immune system to recognise cancer cells, so you may continue to benefit. Although there is a risk of severe side effects, it may be reassuring to know that many people experience only mild side effects. 

Question checklist

It is important to ask your specialist questions, especially if you feel confused or uncertain about your treatment. You may want to include some of the questions below in your list.

  • Is immunotherapy available as part of my treatment plan? If not, why not? Would other treatment options be better for me?
  • How do I find out about clinical trials? Are there any nearby that might be right for me?
  • Which immunotherapy drug are you recommending? Does it have different names?
  • What percentage of people with this type of cancer respond to immunotherapy?
  • How often have you prescribed this treatment? Has it worked well for your other patients?
  • What do you expect the immunotherapy to do to the cancer? Will it be my only treatment?
  • How much will immunotherapy cost? Is there any way to reduce the cost if I can’t afford it?
  • How often will I receive immunotherapy?
  • How long will I have treatment?
  • Where will I have treatment?
  • What side effects should I watch out for or report? Can I get some written information about them?
  • Am I likely to get all of the side effects on the list? Who do I contact if I get side effects? How can side effects be managed?
  • Will I have to pay for extra medicines to help manage side effects?
  • Can I take my other medicines while I am having immunotherapy?
  • Can I have the flu, COVID-19 or other vaccines?
  • How will I know if the treatment is working?


Knowing if it is working

You will have regular check-ups, blood tests and different types of scans to check whether the cancer has responded to the treatment. It may take some time to know if immunotherapy has worked because people often have a delayed response. In some cases, the cancer may appear to get worse before improving.

You may wonder whether having side effects means the immunotherapy is working. Side effects are a sign that the treatment is affecting your immune system in some way, but this may or may not mean the treatment is affecting the cancer. Many people with mild side effects have still seen improvements.

A good response from immunotherapy will make the cancer shrink or disappear. In some cases, the cancer remains stable, which means it does not grow but also does not shrink or disappear. People with stable disease often continue to have a good quality of life.

Unfortunately, checkpoint inhibitors do not work for everyone. Some cancers will not respond to the treatment at all, or the cancer cells can become resistant to the treatment even if it works at first. This can be very disappointing, but your cancer specialist will help you explore other treatment options if this happens.


Understanding Immunotherapy

Download our Understanding Immunotherapy fact sheet to learn more

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Expert content reviewers:

Dr Jenny Lee, Medical Oncologist, Chris O’Brien Lifehouse, NSW; Prof Michael Boyer, Medical Oncologist and Chief Clinical Officer, Lung and Thoracic Cancer, Chris O’Brien Lifehouse, and Central Clinical School, The University of Sydney, NSW; A/Prof Christine Carrington, Senior Consultant Pharmacist Cancer Services, Princess Alexandra Hospital, QLD; Dr Inês Pires da Silva, Medical Oncology Fellow, Melanoma Institute Australia and Westmead and Blacktown hospitals, NSW; Sandra Donaldson, 13 11 20 Consultant, Cancer Council WA; Sherry Gilbert, Consumer; Marilyn Nelson, Consumer; Julie Teraci, Skin and Melanoma Cancer Nurse Coordinator, WA Cancer and Palliative Care Network, North Metropolitan Health Service, WA; Helen Westman, Lung Cancer Nurse Coordinator, Cancer and Palliative Care Network, Royal North Shore Hospital, NSW.

Page last updated:

The information on this webpage was adapted from Understanding Immunotherapy - A guide for people affected by cancer (2021 edition). This webpage was last updated in August 2021.

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