We learned last year at the San Antonio Breast Cancer Symposium (SABCS) that 10 years of tamoxifen treatment is better than what had been the standard five years. Another study sought to confirm these findings.
Taking tamoxifen for 10 years significantly cut the risk of dying among women with breast cancers driven by estrogen, according to the new study.
Mortality risks were cut by 50 percent starting 10 years after diagnosis, the researchers found.
Tamoxifen is given after active treatment for breast cancer is completed.
This new British study – called aTTom (Adjuvant Endocrine Therapy for Breast Cancer) – was led by Richard G. Gray, MA, MSc, a professor of medical statistics at the University of Oxford in the United Kingdom.
The results of the aTTom study demonstrated the same benefits of tamoxifen therapy as the original study, called ATLAS (Adjuvant Tamoxifen, Longer Against Shorter).
According to Gray and his team, hundreds of thousands of women around the world take tamoxifen after being treated for early-stage ER+ (estrogen receptor positive) breast cancer.
In previous trials, the medication has been shown to cut the risk of dying from breast cancer by roughly 33 percent when taken for five years.
For this new trial, Gray and colleagues followed breast cancer survivors for 15 years.
The results showed that 10 years of tamoxifen use not only cut mortality rates by a third in the first 10 years but also by half in the following years.
“These results confirm the data from ATLAS presented at SABCS 2012 and suggest in women where the risk of endometrial cancer is low (such as premenopausal women or women post-hysterectomy) that 10 years of tamoxifen therapy is likely to be appropriate,” Adam Brufsky, MD, PhD, professor of medicine at the University of Pittsburgh School of Medicine, told dailyRx News.
For this study, nearly 7,000 women in the UK were randomly assigned to take tamoxifen for five years or for 10 years.
The researchers found the following:
- Women taking tamoxifen for 10 years had fewer recurrences of breast cancer than those who took the drug for five years (16.7 percent versus 19.3 percent, respectively).
- Duration did not affect recurrence or mortality rates within five to nine years of diagnosis.
- Starting in year 10, women who took tamoxifen for a decade had a 25 percent lower recurrence rate and a 23 percent lower death rate than the women who took the drug for five years.
Tamoxifen can have serious side effects in some women, including an increased risk of uterine cancer. When looking at the number of cases of cancer compared to the lives extended, the authors concluded that the benefits of taking tamoxifen outweighed the risks.
Tamoxifen is marketed in the US under the brand names Nolvadex and Soltamox.
This study was presented at the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting. This research was supported by Cancer Research UK and the UK Medical Research Council. No authors disclosed any possible conflicts of interest.
It should be noted that all research is considered preliminary before it is published in a peer-reviewed journal.