Tamoxifen Protects Against Breast Cancer For Years After Treatment Ends

A new study shows that tamoxifen protects high-risk women against breast cancer for as long as a decade after treatment ends. Joyce Noah-Vanhoucke, PhD, Archimedes Inc., San Francisco, California, and colleagues conducted the meta-analysis and found that using tamoxifen to prevent breast cancer in postmenopausal women aged <55 years was cost-effective and saved lives.

 

The researchers created a virtual clinical trial filled with simulated patients based on breast cancer incidence and survival rates from the Surveillance Epidemiology and End Results registry. Treatment in the mathematical model followed protocols used in 4 randomized, placebo-controlled trials that evaluated the effectiveness of 5 years of tamoxifen at preventing breast cancer.

 

All women in the simulation were aged <55 years when treatment started and postmenopausal, and all had a Gail risk score of 1.66% or greater, indicating a high risk for breast cancer. The study population was restricted to women aged <55 years to allow a more accurate assessment of tamoxifen's contribution to reducing breast cancer risk or increasing the risk of events such as endometrial cancer and blood clots, which are more common in older women.

 

In the article, published in Cancer, the authors said previous studies that found tamoxifen was not cost-effective due to its side effects profile had based their calculations on the assumption that tamoxifen's prophylactic benefit ended when the drug was stopped. The studies selected for the meta-analysis had extended follow-up that showed benefits did not end with treatment but persisted for another 10 years.

 

For every 1000 women treated with tamoxifen in the original trials, 36 life years were saved or 29 quality-adjusted life years (QALYs), at a cost of $11,530 per QALY. In evaluating results for the subpopulation of women aged <55 years used in the model, the authors said, "Tamoxifen use in this population is forecast to save 85 QALYs per 1000 postmenopausal women age <55 with cost savings of $47,580 compared with no treatment over lifetime follow-up." A total of 69 life years were also saved. Stratifying women according to risk scores showed that as breast cancer risk increased, years saved and QALYs increased while cost per QALY decreased.

 

While tamoxifen is considered effective at helping to prevent cancer, its use as a chemopreventive has been limited because of side effects. The authors said the study showed the benefits of tamoxifen prophylaxis for this patient population compensated for the risks and costs of managing adverse events, even though some were quite serious.