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Benefits of chemotherapy for primary breast cancer

Whether you are offered chemotherapy depends on several factors. Read more about the benefits of chemotherapy and whether chemotherapy is the right treatment for you.

1. Do I need chemotherapy?

If you have primary breast cancer, whether you’re offered depends on factors such as:

  • The size of your breast cancer
  • Whether the are affected
  • The grade of your cancer (how different your cancer cells are from normal breast cells and how quickly the cancer cells are growing)
  • The oestrogen receptor and HER2 status

Our information on pathology results explains these in more detail.

Your general health and any other medical conditions you have will also be considered.

2. What are the benefits of chemotherapy?

The benefits of chemotherapy may be clear for some people but less clear in other cases. Your specialist may use an online program to help estimate the benefit you might expect to get from chemotherapy. They may be able to show you a graph of this information or explain the benefit as a percentage.

Genomic assays

When the benefit of chemotherapy is less certain, your treatment team may suggest a test called a genomic assay. You may hear it called gene expression profiling or gene assays.

These tests look at groups of genes found in the breast cancer. They help identify who is most likely to benefit from chemotherapy and how likely the cancer is to return ().

The tests are carried out on breast tissue removed during surgery, usually in a laboratory away from your hospital. Genomic assays are not suitable for everyone and sometimes do not provide a clear answer.

If any of these tests are suitable for you, your treatment team will discuss this with you. 

Genomic assays which may be offered are:


EndoPredict is a test that predicts how likely breast cancer is to spread to somewhere in the body within 10 years in people who will be taking for at least 5 years.

Oncotype DX

Oncotype DX is a test that predicts how likely breast cancer is to come back after surgery and the likely benefit of having chemotherapy.

The test gives a score between 0 and 100, and people who score above a certain number are more likely to be offered chemotherapy.


Prosigna is a test that predicts how likely breast cancer is to spread to somewhere in the body within 10 years in people who will be taking hormone therapy for at least 5 years.

3. Making decisions

You may be asked to decide if you want to have chemotherapy. Making this decision is a personal one. You’ll need to weigh up the likely benefits against the potential side effects.

You can talk it through with your treatment team, who can answer your questions and support you with your decision.

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Quality assurance

This information was published in July 2021. We will revise it in July 2023.

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