Immunotherapy: Supporting the Immune System Against Cancer

What is it?

Immunotherapy is the general name for treatments that help the body’s own immune system recognise and fight cancer cells. The most widely used in oncology today are antibodies called checkpoint inhibitors.

Instead of poisoning the tumour directly, these drugs loosen the brake mechanism between the immune cell and the tumour. For this reason both the effect and the pattern of side effects differ from chemotherapy. In patients who benefit, the response can last longer than with chemotherapy; in those who do not, other options are moved to. The check-up interval and duration are discussed from the outset according to the tumour type.

How does it work?

Pembrolizumab and nivolumab bind to the PD-1 protein, atezolizumab and durvalumab to the PD-L1 protein, and ipilimumab to the CTLA-4 protein. In some patients the tumour hides from the immune system using these proteins. When the drug reduces this hiding, T cells can recognise the tumour again.

The response may not appear immediately. On some imaging studies the tumour may first appear to grow and then shrink; this is called pseudoprogression and is interpreted by an experienced team.

In which cancers is it used?

Melanoma, non-small cell lung cancer, kidney cancer, bladder cancer, some head and neck tumours, Hodgkin lymphoma and selected tumours with high MSI or high tumour mutational burden are among the examples. There are also regimens in which it is given together with chemotherapy or targeted drugs.

Which treatment is appropriate is discussed at the tumour board, with the relevant specialties taking part, by considering the type, stage and molecular features of the cancer and the person’s general condition together.

How is it given?

It is usually given intravenously every two, three, four or six weeks. Depending on response and tolerance, the duration may be months or longer. Before each course, symptoms are reviewed and a blood test is done.

Some immune-related side effects can appear even after treatment has ended. For this reason follow-up does not end on the end date. Live vaccines and drugs that suppress immunity are discussed separately.

During follow-up, blood tests, imaging and symptom review are read together. The dose or date may be changed according to side effects and organ function. The list of medicines used at home is updated at every visit. Sudden fever, shortness of breath, uncontrolled diarrhoea or bleeding should be reported the same day.

Possible side effects

Fatigue, rash, itching, diarrhoea, cough and shortness of breath, changes in thyroid or pituitary hormones and raised liver tests may occur. When the immune system turns against its own organ, colitis, pneumonitis or hepatitis can develop.

New-onset diarrhoea, shortness of breath or severe fatigue should be reported without waiting. The reaction can be suppressed with drugs such as corticosteroids; early intervention reduces organ damage.