Cancer treatment is changing rapidly. Alongside long-established chemotherapy and radiotherapy, immunotherapy — a type of biological treatment that uses drugs to harness the body’s own defences — is increasingly providing longer-lasting control of many cancers. By activating a person’s immune system, immunotherapy helps the body’s immune cells recognise and fight cancer cells more effectively.
The immune system — made up of white blood cells and the organs and tissues of the lymphatic system — can often recognise and destroy abnormal cells. Cancer cells, however, may change their surface proteins or other features so they are less visible to the immune system. Over the past century there have been many attempts to use the immune response against tumours, and recent technological advances have produced drugs that target the molecular “checkpoints” used by cancer cells to switch off immune attacks. These checkpoint inhibitors are now among the most widely used immunotherapies; later sections explain the main types, how they are given, possible side effects and who may benefit.
What is Immunotherapy?
Cancer cells arise from the body’s own tissues but often differ from healthy cells in ways that help them avoid detection. The immune system — a network of white blood cells and lymphatic organs — normally recognises and removes abnormal cells, but cancer cells can undergo changes that make them less visible. One common mechanism is expression of proteins on the tumour surface that inhibit immune attack; for example, some tumours express PD‑L1, which can bind PD‑1 on T cells and switch them off. Mutations and other alterations in cancer cells further reduce the immune response, so the body’s natural ability to destroy cancer cells can be weakened or lost.
Immunotherapy is a type of biological therapy that uses drugs to boost or restore the immune system’s capacity to recognise and attack cancer. These treatments work in different ways — some remove the molecular “brakes” on immune cells, others increase the number or activity of immune cells, and some mark cancer cells so they are easier for the immune system to find. Later sections cover the main types of immunotherapy and how they are used in cancer care.
What are the Types of Immunotherapy?
Immunotherapy strengthens the immune system so it can better recognise and attack cancer. It works by activating or increasing the number of immune cells (such as macrophages, natural killer cells and T lymphocytes), by removing molecular brakes that limit immune responses, or by marking cancer cells so they are easier to find. Below are the main types of immunotherapy in current use or development.
- Checkpoint inhibitors: These drugs block checkpoint proteins (for example PD‑1, PD‑L1 or CTLA‑4) that cancer cells exploit to turn off T cells. By releasing that brake, checkpoint inhibitors allow T cells to attack cancer cells. They have produced durable responses in several cancers and are among the most widely used immunotherapies today.
Other established or investigational immunotherapy approaches include:
- Adoptive cell therapy / T cell transfer: T cells are taken from a patient’s tumour or blood, expanded or genetically modified in the laboratory, and then returned to the patient. This cell therapy can re‑establish an immune attack on cancer cells and includes approaches such as CAR‑T for some blood cancers.
- Cytokines (interleukins and interferons): Cytokines are signalling proteins (for example interleukins, interferons, GM‑CSF) that stimulate immune cell proliferation and activity. They can be given by injection (subcutaneous, intramuscular or intravenous) to boost immune responses and can also affect tumour blood supply.
- Monoclonal antibodies: Lab‑made antibodies can mark cancer cells for immune recognition, block growth signals, or carry toxic payloads (radioactive substances or cytotoxic drugs) directly to cancer cells — a targeted way to combine immunological targeting with cancer treatments.
- Oncolytic viruses: Certain engineered viruses preferentially infect and kill cancer cells and can stimulate an immune response against the tumour.
- Vaccines and adjuvants: Cancer vaccines and adjuvants aim to provoke an antibody or T cell response against tumour‑specific targets. Adjuvants enhance vaccine responses by stimulating the immune system.
- Interferons and interleukins (endogenous mediators): Interferons (IFNs) can slow tumour growth by disrupting cancer cell proliferation, while interleukins (ILs) encourage immune cell division and maturation and increase antibody production against cancer cells.
Each type of immunotherapy has a different mechanism and is used for different cancers or clinical situations. For example, checkpoint inhibitors are widely used in melanoma, lung and bladder cancers, while adoptive cell therapy (cell therapy) has proven effective in certain blood cancers. Many approaches are being tested in clinical trials to extend benefits to more types of cancer.
See the next sections to learn when immunotherapy is applied, how it is given, and the possible side effects patients may experience.
When is Immunotherapy Applied?
Immunotherapy is used in several clinical situations. It began as a treatment for metastatic (advanced) cancer but is now often used alongside chemotherapy or radiotherapy and, in some cases, in earlier stages of disease (neoadjuvant or adjuvant settings) to improve long‑term control. Clinicians may give immunotherapy on its own or combine it with other cancer treatments depending on the type of cancer and the individual patient’s circumstances.
Common scenarios include advanced/metastatic disease where checkpoint inhibitors can produce durable responses, use before surgery (neoadjuvant) to shrink tumours, and use after surgery (adjuvant) to reduce the risk of recurrence. Patient selection often depends on tumour type and whether molecular tests (for example PD‑L1, MSI or TMB) indicate a likely benefit — see the patient selection section for more on tests and eligibility.
How is Immunotherapy Applied?
Most modern immunotherapy drugs — particularly checkpoint inhibitors — are given by intravenous infusion in a clinic or day‑ward, similar to many chemotherapy regimens. Infusion times and schedules vary by drug: some agents are administered every 2–3 weeks, others every 4–6 weeks. Patients usually have baseline blood tests and are monitored during and after the infusion for immediate reactions.
There is generally no complex preparation required beforehand, but specific instructions (for example about vaccinations, concurrent medicines or acute infections) depend on the individual drug and the patient’s overall health. Your treating oncology team will give precise guidance on the infusion schedule, monitoring and any necessary precautions.
What are the Side Effects of Immunotherapy?
Immunotherapy side effects differ from those of classical chemotherapy. Because these treatments boost the immune response, the immune system can sometimes attack healthy tissues. These immune‑related adverse events may affect many organs rather than causing the typical chemotherapy problem of hair loss — although side effects vary by drug and by person.
Common side effects of immunotherapy include:
- Skin: rash or itching.
- Gastrointestinal tract: diarrhoea or colitis (which can be serious).
- Endocrine glands: thyroid dysfunction (hypothyroidism or hyperthyroidism), adrenal or pituitary problems.
- Liver: hepatitis with raised liver enzymes.
- Lungs: pneumonitis (shortness of breath or cough).
- Kidneys: nephritis (changes in kidney function).
The severity of side effects ranges from mild to life‑threatening. Management commonly involves pausing treatment and, when needed, giving immunosuppressive drugs such as corticosteroids under specialist supervision. Because early recognition matters, patients should report new symptoms promptly to their oncology team — for example persistent diarrhoea, breathlessness, unexplained tiredness, or changes in mood or weight.
If you or someone you care for is receiving immunotherapy, your treating clinician will explain likely side effects for the specific drug, how they are monitored (blood tests and symptom checks), and when to seek urgent advice.
Who is Treated with Immunotherapy in Cancer, and for How Long?
Eligibility for immunotherapy depends on the type and stage of the cancer, plus specific features of the tumour. In many cancers, clinicians use molecular tests on the pathology specimen to guide treatment decisions — common biomarkers include PD‑L1 expression, microsatellite instability (MSI) and tumour mutational burden (TMB). Some indications for immunotherapy are biomarker‑driven, while others may be approved regardless of testing; your medical oncology team will interpret test results alongside clinical evidence to decide whether immunotherapy is appropriate.
How long a patient remains on immunotherapy varies. In clinical practice many patients continue treatment as long as the cancer remains controlled and side effects are manageable. Some clinical trials and guidelines explore fixed‑duration approaches or stopping after a defined period of response, and research continues to define optimal durations for different cancers and drugs.
Decisions about starting, continuing or stopping immunotherapy should be made by a medical oncology specialist in discussion with the patient, taking into account likely benefits, possible side effects and alternative cancer treatments (including clinical trials). If you are considering immunotherapy, ask your clinician about relevant tests, potential outcomes for your type of cancer (for example bladder, skin or lung cancers), and whether a clinical trial might be an appropriate way to access new immunotherapies or shorter treatment courses.
