A trial of mercaptopurine and methotrexate for advanced breast or ovarian cancer in people with a BRCA gene fault (6MP-BRCA)

Cancer type:

Breast cancer
Ovarian cancer




Phase 2

This trial looked at mercaptopurine and methotrexate for people with breast or ovarian cancer who had an inherited fault in the BRCA1 or BRCA2 gene. 

The trial was supported by Cancer Research UK. It was open for people to join between 2011 and 2014. The team published the results in 2020.

More about this trial

This trial was for people whose cancer had grown around the original area (locally advanced cancer) or had spread to another part of the body. 

It was for people with:

Fallopian tube cancer and primary peritoneal cancer are similar to ovarian cancer, and doctors treat them in the same way.

When this trial was done, people with cancer related to a BRCA gene fault had the same treatment as those whose cancer was not related to a gene fault. But we knew from research that these cancers may be more sensitive to certain types of chemotherapy.

In this trial, researchers looked at 2 chemotherapy drugs, mercaptopurine (6MP) and methotrexate. Mercaptopurine had already been used to treat leukaemia Open a glossary item. Doctors often give it alongside methotrexate.

The main aims of this trial were to find out:

  • how well mercaptopurine and methotrexate works for breast cancer, ovarian cancer, fallopian tube cancer or primary peritoneal cancer in people with a BRCA gene fault
  • what the side effects are

Summary of results

The trial team found that mercaptopurine and methotrexate didn’t work very well for people with breast cancer who had a change in a BRCA gene. But it seemed to work for a small number of people with ovarian cancer who had a change in the BRCA gene.

About this trial
The people taking part in this trial had either advanced breast cancer or ovarian cancer, and a change in the BRCA1 or BRCA2 gene.

They had all had at least one course of treatment Open a glossary item before. But their cancer had either continued to grow or had come back after treatment.

Everyone taking part had the same treatment – mercaptopurine (6MP) and methotrexate chemotherapy. 

A total of 67 people took part in this trial:

  • 57 people with ovarian cancer
  • 10 people with breast cancer

They all had a change in one of the BRCA genes:

  • 40 people (60%) had a change in BRCA1
  • 27 people (40%) had a change in BRCA2

The research team looked at how well the treatment was working after 2 months. 

They were able to do this for 44 of the people who took part, and found that the cancer had:

  • got a bit smaller in 1 person
  • stopped growing in 21 people
  • continued to grow in 22 people

They looked at how long it was before the cancer started growing again, and found it was nearly 2 months. But for 5 people (7%) it hadn’t started to grow again more than 6 months later. All 5 of these people had ovarian cancer.

Quality of life
The research team were not able to assess how the treatment affected people’s quality of life Open a glossary item. This is because only a very small number of people completed the questionnaires. 

Blood tests
The research team looked at the level of mercaptopurine in people’s blood to see if that affected how well treatment worked. They didn’t find a link between the two.

They also looked at the level of a protein (enzyme) called TPMT (thiopurine methyltransferase) in people’s blood. TPMT helps the body get rid of mercaptopurine. If you have a low level, you are more at risk of having serious side effects. 

The team found that the 5 people whose ovarian cancer stopped growing for at least 6 months all had a high level of TPMT.

Side effects
Just over 9 out of 10 people (91%) who took part at had least 1 side effect. Some were mild or didn’t last long. But just over 6 out of 10 people (61%) had more serious side effects.

The more serious side effects included tummy (abdominal) pain and a drop in red and white blood cells.

12 people taking part decided to stop treatment because of the side effects they were having.

The trial team concluded that the combination of mercaptopurine and methotrexate didn’t work very well for people with breast cancer and a change in a BRCA gene. It did work a bit better for a small group of people with ovarian cancer and a change in a BRCA gene.

They say that further trials of this treatment for this group of patients are unlikely. And that there are other treatment options that may work better.

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

Dr Shibani Nicum

Supported by

Cancer Research UK
Experimental Cancer Medicine Centre (ECMC)
NIHR Clinical Research Network: Cancer
University of Oxford

Other information

This is Cancer Research UK trial number CRUK/10/049.

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.

Last reviewed:

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