An international multicentre study of tamoxifen versus placebo in women at increased risk of breast cancer
Breast cancer is the most common cancer in women in the UK. Some women face a higher risk of developing it due to their family history or certain non-cancerous breast changes found in past biopsies. This trial investigates whether taking a hormone-blocking drug called tamoxifen can safely prevent breast cancer. Tamoxifen is already widely used to treat breast cancer, but researchers want to see if it can stop it from starting in the first place. Women aged 35 to 70 who have an increased risk take part. Half receive a daily tamoxifen tablet, and half receive a harmless dummy pill (placebo). Neither the women nor their doctors choose which pill they get. Participants have regular check-ups and yearly mammograms to protect their health. The study aims to find reliable ways to protect women who are at higher risk.
At a glance
What is this study about?
Many women worry about breast cancer, particularly if their mother, sister, or other close relatives have had the disease. For some, a family history or specific non-cancerous changes in breast tissue can significantly raise their chances of getting breast cancer in their lifetime. Currently, options for lowering this risk are limited, which is why researchers are studying preventative medicines.
This study tests a tablet called tamoxifen. Tamoxifen works by blocking oestrogen, a natural female hormone that can encourage certain breast cancer cells to grow. While tamoxifen has helped treat breast cancer for many years, doctors want to know if giving it early to healthy women at higher risk can stop tumours from forming at all.
To be sure the medicine works, the trial compares tamoxifen against a dummy tablet known as a placebo. A computer randomly decides who receives tamoxifen and who receives the placebo. Comparing both groups allows researchers to see clearly whether the real drug prevents more cancers than the dummy pill, and what side effects it might cause.
Taking part helps doctors understand whether medicines can be used across the NHS to protect future generations of women who carry a higher genetic or familial risk of breast cancer.
Key takeaways
- Tests whether the drug tamoxifen can prevent breast cancer in women at increased risk.
- Open to women aged 35 to 70 with a significant family history or high-risk breast biopsy results.
- Half of the participants receive tamoxifen, and half receive a harmless dummy pill (placebo).
- Requires taking a daily tablet and attending yearly check-ups and mammograms.
- Participation is entirely voluntary, and you can stop at any time.
Who may be eligible?
This trial is for women aged between 35 and 70 who do not currently have breast cancer. To join, you must have had a routine mammogram within the last 12 months that showed no signs of cancer, and you must be willing to attend regular hospital check-ups.
Eligibility depends on your age and your personal or family risk. Younger women (aged 35 to 44) generally need a stronger family history, such as two or more close relatives diagnosed with breast cancer at a young age. Women aged 45 to 70 may qualify with fewer affected relatives or if a close relative had cancer in both breasts.
You may also qualify if you have had a past breast biopsy that showed certain non-cancerous tissue changes. These include conditions called atypical hyperplasia or lobular carcinoma in situ (LCIS), which are known to raise future risk.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am a woman aged between 35 and 70.
- I have had a mammogram in the past year showing no cancer.
- I have close blood relatives who have had breast cancer.
- OR I have had a biopsy showing non-cancerous breast changes like LCIS or atypical hyperplasia.
- I do not currently have breast cancer.
What does participation involve?
If you join the trial, you will be asked to take one tablet every day for up to five years. You will be randomly assigned to receive either tamoxifen or a placebo. You will have clinic appointments every few months at first, and then once a year. At these visits, the trial team will check your general health, discuss any side effects, and arrange your regular yearly mammograms. After finishing the course of tablets, researchers will stay in touch for several years to track your long-term health.
Potential risks and benefits
Locations (1)
- Wolfson Institute of Preventive MedicineUnverifiedLondon, England
Common questions
What is a placebo?
A placebo is an inactive tablet that looks and tastes identical to the real medicine. It helps researchers prove whether any health changes are genuinely caused by the drug itself.
Can I choose to take tamoxifen instead of the placebo?
No. A computer assigns you to a group by chance. Neither you nor your doctor can choose, which ensures the study results are completely fair and unbiased.
Will I still need breast screenings during the trial?
Yes. You will continue to have regular mammograms, usually once a year, to closely monitor your breast health.
What happens if I get unpleasant side effects?
You should tell your study team straight away. They can offer advice or treatments to help manage side effects, or help you safely stop taking the tablets if needed.
Does taking part guarantee I will not get breast cancer?
No. Tamoxifen may reduce the risk, but it cannot completely prevent cancer. This is why regular checks and mammograms remain very important.
How to find out more
Joanna Zahedi
Always speak to your GP or specialist before deciding to take part in a study.
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