Weighing the Risks and Benefits of Tamoxifen as Chemoprevention in High-Risk Women

Hazel Nichols, PhD

A new study has found that while the breast cancer prevention drug tamoxifen’s benefits outweigh its risks, the drug isn’t right for all women.

The study, which was published in the Journal of the National Cancer Institute this month, was headed by Hazel Nichols, PhD, an assistant professor of epidemiology in the University of North Carolina Gillings School of Public Health.

Nichols said part of the drive for doing this study was the fact that few women eligible to take tamoxifen for breast cancer prevention are actually choosing to take it, although it’s been shown to reduce invasive breast cancer risk.

“Tamoxifen is very good at preventing breast cancer, but it also has to be weighed against an increased risk of uterine cancer, stroke, or blood clotting negative effects,” Nichols said in a statement.

The study uncovered tools that can help women and their doctors determine whether preventive drugs like tamoxifen are right for them.

Using a mathematical tool developed at the National Cancer Institute, the researchers were able to weigh the risks and benefits of taking the drug for a group of 788 women who were taking tamoxifen and did not have a history of breast cancer. The analysis took the women’s age, race, breast cancer risk, and risk for potential serious side effects of tamoxifen, such as stroke, uterine cancer, and cataracts, into account.

They found that the drug’s benefits outweighed the risks for 74% of the women included in the analysis, but not for 20% of the participants.

The study found that women who had hysterectomies before starting the drug were 11 times more likely to have a favorable risk-to-benefit profile, and younger women were also more likely to benefit.

However, African-American women were 65% less likely than white women to see their benefits exceed risks associated with taking the drug.

The study also found that many women stopped taking the drug before the recommended 5 years were up. Out of the 788 tamoxifen users in the study, 46% stopped taking the drug before the recommended 5 years.

While the study looked at several factors such as age, race, and breast cancer risk, Nichols said none of those were strong predictors of who decided to stop taking tamoxifen early.

Nichols said the study’s finding that the benefits did not outweigh the risks for 20% of the women is a “reminder” that factors like a woman’s age and her hysterectomy status should be considered when making decisions about chemoprevention.

“It’s important because it highlights that the estimated benefit is not the same for all women, and so women need to go and have a very specific conversation with their providers about what their health looks like at that time, and whether this is a reasonable option for them,” said Nichols.

Nichols HB, DeRoo LA, Scharf DR, Sandler DP. Risk-benefit profiles of women using tamoxifen for chemoprevention. J Natl Cancer Inst. 2014; doi: 10.1093/jnci/dju354.