Dr AlHilali Consultant Clinical Oncologist
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Treatment decisions Understanding treatment

Chemotherapy, immunotherapy and targeted therapy: how do they differ?

How common cancer drug treatments work, why the treatment name does not tell you its aim and why side effects differ.

Written and clinically reviewed by Dr AlHilali Consultant Clinical Oncologist

Published Clinical review

Chemotherapy, immunotherapy and targeted therapy are different ways of treating cancer with medicines. They are often described as systemic treatments because the medicine can reach cancer cells in different parts of the body.

The name of the treatment does not tell you whether its aim is cure, reducing the risk of recurrence, controlling cancer or relieving symptoms. That needs a separate explanation.

In this article

Chemotherapy

Chemotherapy interferes with the growth and division of cells. Cancer cells may be affected, but healthy tissues can be affected too. This helps explain possible effects on blood counts, the mouth, bowel and hair.

There are many chemotherapy medicines and combinations. They do not all have the same side effects, schedule or benefit. Treatment may be given through a vein, as tablets or by another route.

Black-and-white photograph of sealed chemotherapy medicine vials arranged in two rows.
Chemotherapy vials in a historical NCI photograph (1986). These bottles do not depict immunotherapy or targeted therapy, or identify which treatment is suitable for someone. Proportionally resized and compressed; no crop. Photograph: Bill Branson, National Cancer Institute. Source · Public domain

Immunotherapy

Immunotherapy uses the immune system to help attack cancer. One group, immune checkpoint inhibitors, changes signals that normally restrain an immune response.

It is not suitable for every cancer or every person. It can also cause inflammation in healthy organs. New symptoms need to be reported, including symptoms appearing after treatment has finished. Being different from chemotherapy does not mean it is automatically gentler or safer.

Targeted therapy

Targeted treatments act on particular processes or features involved in cancer growth. For some medicines, testing the tumour for a relevant biomarker helps determine whether the treatment might be useful.

Targeted does not mean that only cancer cells are affected. Healthy tissues can be affected and significant side effects are possible. The categories can overlap: some medicines are described using more than one of these terms.

Why might treatments be combined?

Different approaches may contribute to the same treatment aim. A drug may be given with another drug, surgery or radiotherapy. The combination should be supported by evidence for that cancer and clinical situation.

Hormone treatments are another important group used for cancers whose growth is influenced by hormones. Not every cancer medicine fits neatly into the three headings above.

Ask about the actual medicines

Useful questions are:

  • What are the names of my medicines and what is each intended to do?
  • Is a tumour test needed before choosing them?
  • Which side effects need an immediate call?
  • How will benefit and side effects be assessed?

Do not compare treatment strength by whether it is a tablet or an infusion. Ask for instructions specific to your plan, including an out-of-hours contact number.

Sources

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