Context

• The three major forms of treatment for any cancer are surgery (removing the cancer), radiotherapy (delivering ionising radiation to the tumour), and systemic therapy (administering medicines that act on the tumour). 
• Surgery and radiotherapy have been refined significantly over time – whereas advances in systemic therapy have been unparalleled. 
• A new development on this front, currently holding the attention of many researchers worldwide, is CAR T-cell therapy.

Chemo and immunotherapy

• Systemic therapy’s earliest form was chemotherapy. When administered, chemotherapy preferentially acts on cancer cells as they have rapid unregulated growth and poor healing mechanisms. Chemotherapeutic drugs have modest response rates and significant side-effects as they affect numerous cell types in the body.
• The next stage in its evolution was targeted agents, a.k.a. immunotherapy: the drugs bind to specific targets on the cancer or in the immune cells that help the tumour grow or spread. This method often has fewer side-effects as the impact on non-tumour cells is limited. However, it is effective only against tumours that express these targets.

What are CAR T-cells?

• Chimeric antigen receptor (CAR) T-cell therapies represent a quantum leap in the sophistication of cancer treatment. Unlike chemotherapy or immunotherapy, which require mass-produced injectable or oral medication, CAR T-cell therapies use a patient’s own cells. 
• They are modified in the laboratory to activate T-cells, a component of immune cells, to attack tumours. These modified cells are then infused back into the patient’s bloodstream after conditioning them to multiply more effectively.
• The cells are even more specific than targeted agents and directly activate the patient’s immune system against cancer, making the treatment more clinically effective. This is why they’re called ‘living drugs’.

Where is it used?

• As of today, CAR T-cell therapy has been approved for leukaemias (cancers arising from the cells that produce white blood cells) and lymphomas (arising from the lymphatic system). These cancers occur through unregulated reproduction of a single clone of cells: following the cancerous transformation of a single type of cell, it produces millions of identical copies. As a result, the target for CAR T-cells is consistent and reliable.
• CAR T-cell therapy is also presently used among patients with cancers that have returned after an initial successful treatment or which haven’t responded to previous combinations of chemotherapy or immunotherapy.
• Its response rate is variable. In certain kinds of leukaemias and lymphomas, the efficacy is as high as 90%, whereas in other types of cancers it is significantly lower. 
• The potential side-effects are also significant, associated with cytokine release syndrome (a widespread activation of the immune system and collateral damage to the body’s normal cells) and neurological symptoms (severe confusion, seizures, and speech impairment).

How widespread is its use?

• The complexity of preparing CAR T-cells has been a major barrier to their use. 
• The technical and human resources required to administer this therapy are also considerable. Treatments in the US cost more than a million dollars. Trials are underway in India, with companies looking to indigenously manufacture CAR T-cells at a fraction of the cost. 

Reference:

https://www.cancer.gov/about-cancer/treatment/research/car-t-cells