Immunotherapy

What it is

Immunotherapy is a cancer treatment that uses the immune system to find and attack cancer cells; modern cancer immunotherapy began in 1891 with William Coley's early work on immune stimulation. In current oncology, the term usually means medicines or cell-based treatments that either remove the "brakes" on immune cells, mark cancer cells for immune attack, or engineer immune cells to recognise a tumour. The most important practical fact is that immunotherapy is not one treatment. It is a group of treatments, and whether it helps depends strongly on the cancer type, stage, biomarkers, and the specific drug or cell therapy used.

Cancer can grow partly because it avoids immune detection or suppresses immune responses around the tumour. Immunotherapy tries to reverse that. Some immunotherapies are now standard treatment for cancers such as melanoma, lung cancer, kidney cancer, Hodgkin lymphoma, and several others. In India, access is increasing in major cancer centres, but use is still shaped by cost, biomarker testing, and the need for teams experienced in managing immune-related side effects.

Common types include:

Type	What it does	Examples
Immune checkpoint inhibitors	Release inhibitory signals on T cells	PD-1, PD-L1, CTLA-4 inhibitors
Monoclonal antibodies	Bind specific targets on cancer cells or immune pathways	Tumour-targeting antibodies
CAR T-cell therapy	Engineers a patient's T cells to attack cancer	Used mainly in some blood cancers
Cancer vaccines	Stimulate immune recognition of tumour antigens	Preventive and therapeutic approaches
Cytokines / immune stimulants	Boost immune signaling	Interleukin-2, interferon-based approaches

How it works

The immune system can recognise abnormal cells, especially through T cells and antigen-presenting cells. But tumours develop ways to escape. They may reduce antigen presentation, create an immunosuppressive microenvironment, or activate checkpoint pathways such as PD-1/PD-L1 and CTLA-4 that dampen T-cell activity.

Checkpoint inhibitors work by blocking these inhibitory pathways so T cells can attack cancer more effectively. CAR T-cell therapy takes a different approach: T cells are collected from the patient, genetically modified in a lab to recognise a tumour target, expanded, and then infused back. Monoclonal antibodies may directly flag cancer cells for immune destruction, block growth signals, or deliver immune effects indirectly. Cytokines can stimulate immune-cell growth and activity, although older cytokine therapies are often limited by toxicity.

Immunotherapy can also be combined with chemotherapy, radiation, or targeted therapy. This is important because standard treatments may increase tumour antigen release or alter the tumour environment in ways that make immune attack more effective. That is one reason chemo-immunotherapy has become common in several cancers.

Evidence and uses

Evidence for immunotherapy is strong in selected cancers, but responses are uneven. Some patients have deep and durable responses, while others do not benefit at all. This is why oncologists often use biomarker testing and disease-specific evidence before recommending it.

Examples of established uses include:

1. Melanoma: checkpoint inhibitors changed survival outcomes for advanced disease.
2. Non-small cell lung cancer: immunotherapy may be used alone or with chemotherapy, often guided by PD-L1 expression.
3. Kidney cancer: checkpoint inhibitor combinations are widely used.
4. Hodgkin lymphoma: PD-1 inhibitors can be effective in relapsed disease.
5. Some bladder, head and neck, liver, and gastrointestinal cancers: use depends on stage, prior treatment, and biomarkers.
6. Certain blood cancers: CAR T-cell therapy is used in selected leukaemias, lymphomas, and myeloma settings.

Doctors may test biomarkers such as PD-L1 expression, microsatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR), and sometimes tumour mutational burden. These tests do not guarantee response, but they can help estimate the chance that immunotherapy will work.

In India, immunotherapy is available in many tertiary cancer centres, especially in metropolitan areas. The main barriers are affordability, need for pathology and molecular testing, infusion infrastructure, and specialist monitoring. Biosimilars and broader oncology services may improve access over time, but this varies by hospital and state.

Evidence is also strong for some combinations. Chemo-immunotherapy is now standard in several lung and other cancers because chemotherapy can reduce tumour burden and may increase immune visibility of cancer cells. Still, combination treatment can also increase side effects, so the balance of benefit and risk matters.

Safety and interactions

Immunotherapy side effects are different from standard chemotherapy. Instead of mainly causing direct cell damage, these treatments can trigger the immune system to attack normal organs. These are called immune-related adverse events.

Common or important immune-related problems can affect:

Organ/system	Possible problem
Skin	Rash, itching
Gut	Colitis, diarrhoea
Liver	Hepatitis, abnormal liver tests
Lungs	Pneumonitis
Endocrine glands	Thyroiditis, adrenal insufficiency, hypophysitis, diabetes
Kidneys, nerves, heart	Less common but potentially serious inflammation

Some side effects are mild, but others can become emergencies. Severe diarrhoea, shortness of breath, jaundice, chest pain, confusion, or extreme fatigue need urgent medical review. Treatment may require pausing immunotherapy and giving corticosteroids or other immunosuppressive medicines.

Patients should tell their oncology team about all medicines, including steroids, antibiotics, tuberculosis treatment, herbal products, and supplements. Interactions are not always direct drug-drug interactions in the usual sense, but other medicines can affect immune function, infection risk, or side-effect management. People with autoimmune disease, prior organ transplant, chronic viral infections, or poor lung reserve may need especially careful assessment before treatment.

Do not start over-the-counter immune boosters or herbal products during cancer treatment without asking your oncologist or pharmacist. "Natural" products can still affect the liver, kidneys, clotting, or prescribed medicines.

When to see a clinician

See a cancer specialist if you want to know whether immunotherapy is an option for your cancer, especially if you have advanced disease, recurrence, or a pathology report mentioning PD-L1, MSI-H, or dMMR. A medical oncologist can explain whether immunotherapy is standard, optional, or experimental in your situation.

If you are already receiving immunotherapy, contact your treatment team promptly for new symptoms, even if they seem minor. Immune-related side effects can start during treatment or sometimes weeks to months later. Early reporting often makes them easier to treat.

Seek urgent care for severe breathlessness, chest pain, persistent vomiting, dehydration, confusion, high fever, black stools, severe abdominal pain, or rapidly worsening weakness.

Limitations and open questions

Immunotherapy has changed cancer care, but it is not a universal cure. Many tumours do not respond, and some respond only briefly. Biomarkers help, but they are imperfect. A high PD-L1 result does not guarantee benefit, and a low result does not always mean no benefit.

Important open questions include how to predict response more accurately, how long treatment should continue, which combinations are best, and how to reduce serious immune toxicity without reducing anti-cancer effect. Evidence is also still evolving for many newer combinations, earlier-stage use, and some rare cancers.

CAR T-cell therapy and other advanced cell therapies are promising, but they remain complex, expensive, and available only in selected centres. In lower-resource settings, including parts of India, access and supportive care capacity remain major practical limits.

The best way to think about immunotherapy is as a major treatment class with real benefits for some patients, real risks, and a need for individualised decision-making based on cancer type, biomarkers, overall health, and treatment goals.