Ten Years of Adjuvant Tamoxifen Found Superior to Five
AT THE SAN ANTONIO BREAST CANCER SYMPOSIUM
Major Finding: Women randomized to 10 years of adjuvant tamoxifen had a 25% reduction in recurrences and a 29% lower mortality due to breast cancer in years 10-14 after diagnosis, compared with women who stopped the drug after the standard 5 years.
Data Source: The ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) trial included 6,846 women with estrogen receptor–positive early breast cancer.
Disclosures: The ATLAS trial was funded by Cancer Research UK, the UK Medical Research Council, AstraZeneca, the U.S. Army, and EU Biomed. Dr. Gray reported having no financial conflicts.
SAN ANTONIO – Five years of adjuvant tamoxifen in women with estrogen receptor–positive early breast cancer is well established as being excellent therapy with a long-term carryover effect. Now 10 years has been shown to be even better.
A new analysis from the large international ATLAS trial demonstrated that participants randomized to 10 years of adjuvant tamoxifen had a 25% reduction in recurrences and a 29% lower mortality due to breast cancer in years 10-14 after diagnosis, compared with women who stopped the drug after the standard 5 years, Richard Gray, M.Sc., reported at the San Antonio Breast Cancer Symposium.
These findings from ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) are all the more impressive in light of the 2011 Early Breast Cancer Trialists’ Collaborative Group overview analysis, which features 15 years of follow-up of more than 10,000 women in randomized trials pitting 5 years of tamoxifen versus no tamoxifen (Lancet 2011;378:771-84). The meta-analysis showed that 5 years of tamoxifen reduced deaths due to breast cancer by 34% during the first 5 years after treatment ended and by 27% in the subsequent 5 years.
Thus, 10 years of tamoxifen had to compete against a big carryover effect of 5 years of the drug, noted Mr. Gray, professor of medical statistics at the University of Oxford (U.K.).
By multiplying the risk reduction ratios from ATLAS and the Oxford overview, he estimated that 10 years of tamoxifen reduces breast cancer mortality by one-third in the first decade following diagnosis and by fully half in the second decade, compared with no tamoxifen.
Benefits Far Outweigh Risks
The ATLAS analysis involved 6,846 randomized women with estrogen receptor–positive disease. The cumulative risk of recurrence during years 5-14 after diagnosis was 21.4% in women assigned to 10 years of tamoxifen and 25.1% in controls. Breast cancer mortality during years 5-14 was 12.2% in patients on 10 years of tamoxifen and 15.0% in those who stopped after 5 years, for an absolute mortality reduction of 2.8%.