Only about a fifth of women at higher risk of developing breast cancer think they need to take a drug proven to help prevent the disease, according to new research.
Some 72% said they were worried about the long-term effects of tamoxifen, while 57% thought the drug would give them unpleasant side-effects.
The researchers, led by a team from the University of Leeds, asked more than 400 healthy women at a higher risk of breast cancer, from 20 clinics across England, whether they thought they needed to take tamoxifen, as well as their concerns about medication.
They discovered that almost a third (29%) of the women thought doctors prescribed too many medicines, and 35% thought doctors would prescribe fewer drugs if they had more time. Almost a quarter (24%) of the women had experienced bad reactions to medicines in the past.
Just under a quarter (24%) of the women thought people on medication should take regular breaks from the drugs; 23% said they were very sensitive to medicines and 17% believed natural remedies were safer than medicines.
In a follow-up questionnaire, answered by 250 of the same women, researchers found that fewer than 15% were taking tamoxifen despite having discussed preventive therapy with a healthcare professional. Women who believed the medication was less necessary and had more concerns about its use were less likely to be taking tamoxifen at follow-up.
There are some potential side effects with tamoxifen, and other medications that can help prevent cancer, but its vital that they have all the information, so they can make the best choice for them.
The study was funded by Cancer Research UK and published in the journal Clinical Breast Cancer.
Lead author Dr Samuel Smith, a behavioural scientist in Leeds Institute of Health Sciences at the University, said: Women in our study were rightfully considering the potential harms and benefits of using preventive therapy. But some beliefs about the use of medicine were very negative. This appears to be putting some women off tamoxifen, despite its proven ability to help prevent breast cancer in the long term.
We need to make sure health care professionals are adequately equipped to discuss the potential benefits and harms of preventive treatment with their patients so that women are well informed before deciding whether or not to take a drug.
Dr Julie Sharp, Cancer Research UKs head of health information, said: Its understandable that women considering taking a new medicine might have some concerns and that, for some, it wont be the right option.
"There are some potential side effects with tamoxifen, and other medications that can help prevent cancer, but its vital that they have all the information, so they can make the best choice for them.
"If women in this situation have any questions or want more information, they can visit our website or call our cancer nurses for a chat."
Increased risk is defined by NICE as a woman who has at least a 17% lifetime risk of being diagnosed with breast cancer.
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The paper is titled 'Beliefs about medication and uptake of preventive therapy in women at increased risk of breast cancer: Results from a multi-centre prospective study' and is published in the journal Clinical Breast Cancer.