Richard Gray on the Safety and Efficacy of 10 Years of Adjuvant Tamoxifen

Richard G. Gray, MA, MSc, a professor of Medical Statistics at the University of Oxford in the United Kingdom, discusses results from the randomized, phase III aTTom study that examined 10 years of tamoxifen versus the more standard 5 years.

Taking tamoxifen for 5 years results in a 33% reduction in mortality. The study found that the continued use of tamoxifen for 10 years results in an additional 25% reduction, for an overall risk reduction of over 50%.

The main adverse event for treatment with tamoxifen is an increased risk of endometrial cancer. There was a slight increase in the occurence of endometrial cancer with 10 years of tamoxifen compared to 5 years. However, Gray states, for every endometrial cancer death, caused by 10 years of tamoxifen, 30 breast cancer deaths were prevent.

With the ATLAS trial and other trials there is overwhelming evidence suggesting that breast cancer risk is greatly reduced with 10-years of tamoxifen. By and large, the benefits outweigh the risks for utilizing tamoxifen for ten years.

• Administering 10 years of adjuvant tamoxifen reduced the risk of death from breast cancer by over 50% compared to 33% for 5 years
• The occurrence of secondary endometrial cancer was slightly higher with 10 years of tamoxifen
• By and large, Gray believes, the benefits outweigh the risks for utilizing tamoxifen for ten years