Many women who are at high risk of developing breast cancer are not taking the drug tamoxifen – which has been shown to reduce that risk – because they mistake symptoms of early menopause for side effects of the drug.
A study that has been ongoing since 1992, the International Breast Intervention Study (IBIS-I) has demonstrated that the preventative benefits of tamoxifen last for 20 years or more. Yet new data indicates that only 1 in 6 women at high risk for developing breast cancer — those with a family history of the cancer — take tamoxifen, and not all of them that do manage to take it consistently for 5 years as recommended.
Prior research has found that tamoxifen can reduce the likelihood of developing breast cancer by at least 30% in high-risk women.
In the new study, published in the Journal of Clinical Oncology, researchers examined data on 3,823 women who took part in IBIS-1 and received either tamoxifen or a placebo for 5 years.
About 65% of women taking tamoxifen stuck with it for 5 years, compared to 74% of those on placebo. Side effects reported included nausea or vomiting, headaches and gynecological issues.
Of women who reported nausea or vomiting, around 40% quit their treatment, whether they were receiving tamoxifen or a placebo. Researchers found that many women on a placebo experienced nausea, sickness and hot flushes, symptoms also associated with menopause. This leads them to believe many women are incorrectly blaming tamoxifen for side effects that are really part of menopause.
“This suggests that women may be attributing normally-occurring, age-related symptoms, such as those experienced around the time of menopause, to their medication instead,” co-author Ivana Sestak, PhD, of Queen Mary University of London, said in a statement.
“Communicating accurate information on side effects to patients, and highlighting that some naturally-occurring symptoms may occur during the course of therapy, could be a useful approach in encouraging adherence,” she added.
Tamoxifen does have some more serious side effects such as an increased risk of blood clots, strokes and endometrial and uterine cancers, though these are relatively rare.