Six in seven women at risk of breast cancer are opting out of taking a preventative drug called tamoxifen, a new study has found.

Researchers said there were three main factors for why they avoided the drug: fear of side effects, distrust of medication in general and believing cancer was down to fate.

Previous research found those at increased risk of the disease had a reduced risk of around a third after taking the drug, which led to its approval for  prevention. But what else do we know about it?

A new study funded by Cancer Research UK and published in Breast Cancer Research and Treatment asked 258 healthy but ‘at risk’ women across England whether they had agreed to take the drug to help prevent breast cancer developing. Researchers also interviewed 16 women to identify what influenced their decision to take it.

They found just one in seven women had agreed to take it as a preventative measure, with mothers being more likely to take up the offer.

What is tamoxifen?

Tamoxifen is a hormonal therapy drug used to treat breast cancer. It’s most commonly given to women who have been treated for breast cancer to lower the risk of it coming back. But in 2013 the National Institute for Health and Care Excellence (NICE) also approved it for cancer prevention in premenopausal women at increased risk of the disease due to a family history of breast or ovarian cancer.

The drug, which is usually taken daily in tablet form for five years, works by stopping the female hormone oestrogen from encouraging breast cancers to grow.

Women can access the drug through a family history clinic or a genetics clinic, following a referral from their doctor. (If you’re concerned about your risk, speak to your GP.) Melanie Sturtevant, policy manager at Breast Cancer Now says it is “unclear” whether these conversations are always happening in the clinic and that “many GPs lack confidence in discussing the option, with many others not even being aware of it”.

Like many types of medication, it does have its downsides. Sturtevant says the drug “can have some really difficult side-effects for women, most commonly menopausal symptoms such as hot flushes and sleep disturbance”, which can make the decision to take them quite hard.

Other possible side effects include: vaginal discharge, itching or dryness; irregular, lighter or non-existent periods; reduced sex drive; nausea and indigestion; eye problems; effects on the nervous system (for example pins and needles or tingling in the arms and legs, dizziness or taste changes); leg cramps; muscle pain; tiredness; lack of energy; skin rashes; hair thinning; weight gain; and changes in mood and concentration.

There are also more serious side effects, which are rare, such as blood clots and increased risk of womb cancer.

Other preventative measures

Tamoxifen is a form of chemoprevention, a group of risk-reducing drugs that women at increased risk of breast cancer can take. Other drugs include raloxifene and anastrozole, which are often given to postmenopausal women.

Risk-reducing drugs can’t prevent breast cancers developing in all women at increased risk, but they can lower the chances of this happening over a 10-year period.

Mastectomy, where the breasts are removed, can reduce the chances of cancer in high-risk families. According to the NHS, removing as much breast tissue as possible can help to reduce the risk of breast cancer by up to 90% – although it also has risks and side effects too. Problems can include pain or tenderness, swelling, or a build-up of fluid or blood.

There’s also some evidence to suggest lifestyle changes – regular exercise (30 mins a day) and a healthy, balanced diet – might help. Studies have looked at the link between breast cancer and diet, and although there are no definite conclusions, there are benefits for women who: maintain a healthy weight, exercise regularly, and have a low intake of alcohol and saturated fat.

Being breast aware and attending any breast screening you might be eligible for can also help make sure that if you develop breast cancer, it’s spotted as early as possible, giving you the best chance of successful treatment.

There are multiple options out there – all of which carry some degree of risk. Sturtevant says: “Ultimately, while not all women will want to take tamoxifen as it has side-effects as well as benefits, it’s imperative that they are offered the choice and given all the information they need to make an informed decision.”