A trial looking at celecoxib for women with breast cancer (REACT)

Cancer type:

Breast cancer




Phase 3

This trial looked at a Cox-2 inhibitor called celecoxib to see if it stopped early breast cancer coming back. It was open to women who had all of the following:

  • breast surgery 
  • further treatment after surgery
  • breast cancer that didn’t have a large number of the HER2 receptor (HER2 negative breast cancer)

This trial was open for people to join between 2007 and 2012. The team published the results in 2021.

Cancer Research UK supported this trial. 

More about this trial

The usual first treatment for early breast cancer is surgery. Some people also have radiotherapy or chemotherapy. These treatments work well but sometimes the cancer comes back.

When this trial was done, doctors thought that adding celecoxib might lower the chance (risk) of the cancers coming back. 

Celecoxib is a type of drug called a Cox-2 inhibitor Open a glossary item. These are a type of anti inflammatory drug. They block a protein, called Cox-2, that may help cancers to grow.

In this trial researchers compared celecoxib to dummy tablets (placebo Open a glossary item) for people with early breast cancer Open a glossary item.

The aims were to find out:

  • whether celecoxib stops breast cancer from coming back
  • more about the side effects

Summary of results

The trial team found that taking celecoxib for 2 years didn’t stop HER2 negative breast cancer coming back. 

Trial design 
This was a double blinded randomised trial. Neither the women nor their doctor could choose which group they were in. Nor did they know whether they were having celecoxib or the dummy drug. 

A total of 2,639 women took part. 2 out of every 3 women had celecoxib.

1,763 women had celecoxib and 876 women had the dummy drug. 

After surgery to remove their cancer the women had either radiotherapy or chemotherapy. They then had 2 years of treatment with either celecoxib or the dummy drug. 

After a median Open a glossary item follow up of just over 6 years (74.3 months) the trial team looked at the number of women who were living.  And whose cancer had not come back or spread after 5 years. They found that it was:

  • 1,440 (84%) women in the celecoxib group 
  • 712 (83%) women in the dummy drug group


The researchers also looked at the number of women who were living after 5 years. They found this was similar between the 2 groups.  It was:

  • 1,560 women (90%) in the celecoxib group
  • 772 women (91%) in the dummy drug group


Side effects
Having celecoxib didn’t increase heart or certain other common side effects such as sickness or tummy pain. The team found no difference between the side effects reported by the women taking celecoxib and those who had the dummy drug. And the number of side effects reported in both groups were low. 

The team concluded that celecoxib didn’t benefit women with HER2 negative early breast cancer. 

The researchers say that having celecoxib for a longer period of time or having a higher dose might work better. But they would need to run a trial to test this. 

Even so, all trial results help doctors and researchers understand more about different cancers and the best way to treat them. 

Where this information comes from    

We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Professor Charles Coombes

Supported by

Cancer Research UK
Experimental Cancer Medicine Centre (ECMC)
German Breast Group (GBG)
Imperial College London
NIHR Clinical Research Network: Cancer

Other information

This is Cancer Research UK trial number CRUKE/03/015.

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Harriet wanted to try new treatments

A picture of Harriet

“I was keen to go on a clinical trial. I wanted to try new cancer treatments and hopefully help future generations.”

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