A study looking at tamoxifen to prevent breast cancer in premenopausal women (TAM-Prev)

Cancer type:

Breast cancer





This study aimed to find out how many women who had a high risk of developing breast cancer had considered using tamoxifen to prevent it. The study was for women who had not been through the menopause Open a glossary item. The researchers also wanted to see if a substance in the blood called a biomarker Open a glossary item can be used to find out which women may benefit from having tamoxifen.

More about this trial

Some women have an increased risk of breast cancer. We know from research that taking tamoxifen for 5 years can significantly reduce the number of high risk women who develop breast cancer. But tamoxifen cannot prevent breast cancer in all women. And like all medications it has side effects.

The researchers had developed a tool called a Decision Aid. It explains in detail the benefits and risks of taking tamoxifen. The researchers wanted to use this to see if it could help women decide if they wanted to take tamoxifen or not.

The aims of this study were to find out

  • How many women decided to take tamoxifen
  • If biomarkers could identify women who could benefit from having tamoxifen

Summary of results

The study team found that the number of women who decided to take tamoxifen after using the Decision Aid was similar to the number of women who decided to take tamoxifen in other studies that didn’t use this tool.

The study team sent out letters of invitation to 1,279 women who attended the Family History Clinic at the Nightingale and Genesis Prevention Centre, Manchester. Of these, 379 women accepted the invitation to join the study and received the Decision Aid. In total, 136 of the 1,279 women (10%) decided to have tamoxifen.

Halfway through the study, the team updated the Decision Aid after getting feedback from the women. Before they updated the Decision Aid, about 3 out of every 10 women (33%) decided to take tamoxifen. After updating the Decision Aid, the number rose to 4 out of every 10 women (40%).

Women who were at risk of developing breast cancer because they may have the BRCA 2 Open a glossary item  or BRCA 1 Open a glossary item gene change were significantly less likely to take tamoxifen than those who didn’t.

The group that had the highest uptake of tamoxifen was women between 41 to 46 years old and had the highest life time risk of getting breast cancer.

The study team interviewed 30 women, 15 women who had declined tamoxifen and 15 women who had decided to take it. They wanted to find out what influenced the women to make their decision.

They found that there were 4 major themes that influenced their decision.

Impact of possible side effects
The risk of side effects was the main consideration when the women were deciding whether to take tamoxifen or not. Both those who declined tamoxifen and those who decided to take it were concerned about the range of possible side effects. 25 women expressed concern that the impact on their quality of life Open a glossary item would also affect their family, particularly young children. 9 women who decided to take tamoxifen accepted that they might experience many of the side effects, such as hot flushes.

The opinions and knowledge of tamoxifen gained from social groups
All the women sought the opinions of others, especially from women who were taking, or had taken, tamoxifen. 6 women said that the opinions of others strongly influenced their decision not to take tamoxifen.

Their social groups also influenced the women’s view on how well tamoxifen worked as a way of preventing breast cancer. Those who had close friends or family who’d had their cancer come back while taking tamoxifen were doubtful about how well it worked. When they knew women who had taken tamoxifen and whose cancer hadn’t come back, the women were more positive about how well it might work.

Tamoxifen as a cancer drug
For many women, tamoxifen was too closely associated with cancer and deciding whether to take it stirred up painful memories. 7 women expressed concern about how their family and friends would react to their decision to take tamoxifen on a voluntary basis. Some also expressed concern about having to explain to children about their family history of breast cancer.

A reminder of their cancer risk
8 women decided not to take tamoxifen because it was a final recognition that they had a risk of getting breast cancer. For other women, breast cancer wasn’t the only health concern in their families and it may be difficult for them to focus on prevention of breast cancer instead of more pressing or significant diseases.

The researchers also took blood samples to find out if there was a biomarker Open a glossary item that could identify women who may benefit from having tamoxifen.

Firstly they looked at the women’s breast tissue density on mammograms. This is because the less dense the breast tissue, the lower the risk of getting breast cancer.

After a year of tamoxifen, a doctor who specialises in reading mammograms looked at the changes in the density of the women’s breast tissue. They found that for half the women the density of their breast tissue had reduced by more than 10%. When they used an automatic assessment tool, this also showed that breast density had reduced by more than 10% in more than half the women taking tamoxifen.

They then compared changes in certain substances in the blood with changes in breast tissue density seen on a mammogram.

By looking at blood samples taken from women in the study, they found that the level of certain fats called triglycerides was higher in women with reduced breast density.

The study team concluded that the numbers of women in this study who decided to take tamoxifen as a preventative was similar to other studies. Doctors should be aware of the beliefs surrounding using tamoxifen as a preventative and how these beliefs are formed.

They also found that levels of triglycerides in the blood may possibly be used as a biomarker to see who might benefit from tamoxifen.

We have based this summary on information from the team who ran the trial.   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. 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 Gareth Evans

Supported by

NIHR Clinical Research Network: Cancer
The Genesis Breast Cancer Prevention Appeal
NIHR Research for Patient Benefit (RfPB) Programme

Questions about cancer? Contact our information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle 8554

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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