Immunotherapy for Cancer — Types, How Each Works, and Which Cancers Respond

Immunotherapy has changed outcomes for certain cancer patients in ways that would have seemed implausible twenty years ago. People with Stage IV melanoma who were given months are now in long-term remission years later. Some leukaemia patients who had exhausted every other option had complete responses to CAR T-cell therapy. These results are real.

They are also not universal. And the gap between the headlines and the reality of who actually benefits is where most confusion sits. This guide goes through each type of immunotherapy, what it does, which cancers it works for, and what it does not do.

Checkpoint Inhibitors — The Most Widely Used

The immune system has built-in brakes — checkpoints — that prevent it from attacking the body's own tissues. Cancer cells exploit these checkpoints. They express proteins like PD-L1 that bind to receptors (PD-1) on T cells and essentially send a "stand down" signal. The T cell, receiving this signal, does not attack.

Checkpoint inhibitor drugs block this interaction. Block the PD-L1 signal, and the T cell's brake is released. The tumour loses its disguise.

1. PD-1 inhibitors: Pembrolizumab (Keytruda), nivolumab (Opdivo). These bind to the PD-1 receptor on the T cell, preventing PD-L1 from docking and sending the inhibitory signal.

2. PD-L1 inhibitors: Atezolizumab (Tecentriq), durvalumab. These bind to PD-L1 on the tumour cell itself, blocking it from reaching the PD-1 receptor.

3. CTLA-4 inhibitors: Ipilimumab (Yervoy). CTLA-4 is a different checkpoint, active earlier in the immune activation process. Blocking it unleashes T cell activity more broadly.

Combinations of PD-1 and CTLA-4 inhibitors produce stronger responses in some cancers — particularly melanoma and renal cell carcinoma — at the cost of higher rates of immune-related side effects.

4. Which cancers respond:

Melanoma, non-small cell lung cancer (especially high PD-L1), bladder cancer, renal cell carcinoma, Hodgkin's lymphoma, head and neck squamous cell carcinoma, cervical cancer, endometrial cancer, hepatocellular carcinoma, and any tumour with high microsatellite instability (MSI-H) regardless of where it started.

5. Which cancers largely do not respond:

Pancreatic cancer, most brain tumours, colorectal cancers without MSI-H, prostate cancer (with some exceptions).

CAR T-Cell Therapy — Engineered Immunity

This approach does not work with the existing immune system — it engineers new immune cells specifically designed to hunt the cancer.

T cells are collected from the patient's blood. In a specialised laboratory, the cells are genetically modified to express chimeric antigen receptors — CARs — on their surface. These receptors are designed to bind to a specific protein on the cancer cell's surface. The modified T cells are multiplied to large numbers and infused back into the patient.

Once in the body, these CAR T cells hunt down any cell bearing the target antigen. They kill the cancer cell and then multiply further in response to finding targets.

The responses in some blood cancers have been striking. In studies of patients with large B-cell lymphoma who had failed two or more prior therapies, 30 to 40 percent achieved complete remission — meaning no detectable cancer — with CAR T-cell therapy. In acute lymphoblastic leukaemia, particularly in children and young adults, complete remission rates in relapsed/refractory patients have been above 70 percent in some trials.

CAR T-cell therapy is not without serious risk. Cytokine release syndrome — a potentially life-threatening storm of inflammatory proteins released as the T cells activate — is common and can be severe. Neurotoxicity is another serious complication. These require management in specialised oncology units with experienced teams.

Current CAR T approvals target CD19 (B-cell malignancies) and BCMA (multiple myeloma). Research into solid tumour targets is ongoing but has not yet produced the same results as in blood cancers.

Monoclonal Antibodies — Targeted and Specific

Antibodies manufactured in a laboratory to target specific proteins. Some work by directly killing cancer cells. Others flag cancer cells for destruction by the immune system. Others block signalling pathways the cancer needs to grow.

1. Trastuzumab (Herceptin) — targets HER2 protein, overexpressed in 15 to 20 percent of breast cancers and some gastric cancers. Has transformed outcomes in HER2-positive breast cancer.

2. Rituximab — targets CD20 on B lymphocytes. Standard treatment in B-cell non-Hodgkin's lymphoma and chronic lymphocytic leukaemia.

3. Cetuximab and panitumumab — target EGFR. Used in colorectal cancer (only if the tumour does not have KRAS or NRAS mutations) and head and neck cancer.

4. Bevacizumab — targets VEGF, the protein that stimulates blood vessel formation that tumours need to grow. Used across multiple cancer types as part of combination regimens.

Bispecific Antibodies — Newer and Promising

These are engineered antibodies that bind two targets at once — one arm grabs the cancer cell, the other grabs a T cell and pulls it into contact with the cancer cell. Blinatumomab (Blincyto) for acute lymphoblastic leukaemia was one of the first. Newer bispecifics for multiple myeloma and other haematological malignancies are entering clinical use.

What Testing Is Needed Before Starting Immunotherapy

The testing matters as much as the treatment choice.

1. PD-L1 immunohistochemistry — determines whether the tumour expresses PD-L1 and at what level. Required before pembrolizumab monotherapy in lung cancer.

2. MSI/MMR testing — microsatellite instability status. MSI-H tumours respond to pembrolizumab regardless of cancer type.

3. Tumour mutational burden (TMB) — higher TMB is associated with better checkpoint inhibitor response. Testing by next-generation sequencing.

4. HER2 testing — before trastuzumab in breast or gastric cancer.

5. KRAS/NRAS/BRAF testing — before anti-EGFR therapy in colorectal cancer.

All of this testing is available at India's accredited oncology hospitals. For African patients who have received a cancer diagnosis without this workup, it can be completed in India — and the results will determine which immunotherapy, if any, is appropriate.

Immunotherapy at Prime Medical's Partner Hospitals

1. Apollo Proton Cancer Centre, Chennai — Dr. Rakesh Jalali (Medical Director, Neuro Oncology) and Dr. Sapna Nangia manage complex cancer cases including immunotherapy-eligible presentations. The centre has molecular testing capability for the full range of biomarker tests described above.

2. Max Super Speciality Hospital, Saket, Delhi (JCI, NABH, NABL) — Dr. Rohit Nayyar handles cancer care including immunotherapy for solid tumours. Full oncology programme.

3. Fortis Memorial Research Institute, Gurugram (JCI, NABH, NABL) — Multidisciplinary tumour board reviews immunotherapy candidacy for complex cases.

4. Yashoda Hospitals, Hyderabad (JCI, NABH, NABL) — Dr. M. Suneetha. Cancer care including immunotherapy.

5. Sarvodaya Hospital, Faridabad — Dr. Vishnu Hari. Cancer care for patients prioritising accessibility.

6. Fortis Hospital BG Road, Bengaluru — Dr. Niti Raizada and Dr. Saratchandra Pingali. Full oncology programme including immunotherapy.

For patients from Ethiopia, Uganda, Tanzania, and Gambia wanting to understand whether immunotherapy is relevant to their diagnosis — share biopsy reports and imaging with Prime Medical Solutions. A specialist reviews within 48 hours. To book a consultation, call the number on our website.