More than 21,000 women of all ages who were at increased risk of developing breast cancer. (Representational Image)
Five in six women with increased risk of breast cancer turn down drugs likely to prevent the disease, a new study has found.
Researchers at Queen Mary University of London collected data from 26 international studies totalling more than 21,000 women of all ages who were at increased risk of developing breast cancer.
The women in these studies were offered a five-year course of preventive medication to lower their risk of developing the disease.
Overall just one in six 16.3 per cent of women at higher risk chose to take the medication. Those offered the opportunity to take part in trials were more likely to use preventative medications with 25 per cent choosing it compared with nine per cent of women making the decision outside a clinical trial.
The researchers also examined a separate group of 18 studies looking at how likely the women were to complete a full course of drugs.
The studies looked at any medication that is used for breast cancer prevention including tamoxifen and raloxifene, either as given on a clinical trial or by a specialist, when referred by their doctor.
Of the studies that tracked women's use of preventative medications over time, most reported more than 80 per cent of women took the drugs for at least one year. But this declined over time.
Drugs to block cancer-causing hormones and surveillance with an annual mammogram may be offered to certain women with a family history of the disease when they have a moderate to high risk of breast cancer.
"Our important research reveals that only a small proportion of eligible women make the decision to have preventative medication," said Sam Smith, from Queen Mary University of London.
"It's crucial to find out why so many chose not to take the drugs - or stopped taking them before completing the course," he added.
findings were published in the journal Annals of Oncology.