The majority of women at high risk of developing breast cancer decide against prophylactic treatment with tamoxifen, suggest findings of a new study funded by Cancer Research UK and published in Breast Cancer Research and Treatment.

The study found that of 258 healthy women in England with a family history of the disease, six out of seven decided not to take the drug to help prevent it from developing.

Sixteen women were then interviewed in order to determine what factors played a role in their decision, with key reasons found to be a belief that cancer was down to fate, a distrust of medication in general, or fear of side effects would interfere with looking after their family.

The research team, based at the University of Leeds, Northwestern University, University College London and Queen Mary University of London, found women with children were more likely to take up the offer of tamoxifen, and that social class, educational attainment and ethnicity had no effect on uptake.

In 2013, the National Institute for Health and Care Excellence endorsed NHS funding for use of tamoxifen cancer prevention in women at increased risk of the disease due to a family history of breast or ovarian cancer, following research which showed it could lower risk by around a third.

According to the guidelines, doctors should offer tamoxifen for five years to premenopausal women at high or moderate risk of breast cancer, unless they have a past history or may be at increased risk of thromboembolic disease or endometrial cancer, and anastrozole for five years to postmenopausal women unless they have severe osteoporosis.

For postmenopausal women at high risk of breast cancer with severe osteoporosis, but no history or increased risk of thromboembolic disease or endometrial cancer, tamoxifen should for offered, or raloxifene as an alternative for women with a uterus.

“It’s valuable to understand why women might reject tamoxifen, and this research highlights there are a range of complex reasons behind the decision,” said Dr Richard Roope, Cancer Research UK’s senior clinical adviser and GP expert.

“It’s vital more work is done to understand these barriers, improve treatments and ensure doctors are getting the support they need to help women decide whether preventative medication is right for them.”