Research table: Tamoxifen for early breast cancer treatment

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.

Introduction: Tamoxifen improves survival for people with estrogen receptor-positive early breast cancer. Tamoxifen is a pill taken every day for 5-10 years.

Tamoxifen lowers the risk of [1-2]:

• Breast cancer recurrence (a return of breast cancer)
• Breast cancer in the opposite breast
• Death from breast cancer

Taking tamoxifen for more than 5 years

Findings from a large randomized clinical trial showed taking tamoxifen for 10 years reduced the risk of breast cancer recurrence and death more than taking tamoxifen for 5 years [3].

Discuss the benefits and risks of taking tamoxifen for more than 5 years with your health care provider.

Learn more about tamoxifen.

Learn about the side effects of tamoxifen.

Learn about the strengths and weaknesses of different types of studies.

Study selection criteria: Early Breast Cancer Trialists’ Collaborative pooled analyses.

Early Breast Cancer Trialists’ Collaborative Group Pooled Analyses [1-2]
	15-Year Breast Cancer Survival*
	Percent Surviving		Absolute Improvement in Survival with Tamoxifen
	Tamoxifen	No Tamoxifen
Tamoxifen use for 5 years
Overall	76%	67%	9%†
	10-Year Overall Survival‡
	Percent Surviving		Absolute Improvement in Survival with Tamoxifen
	Tamoxifen	No Tamoxifen
Tamoxifen use for 5 years
Lymph node-negative	82%	77%	5%†
Lymph node-positive	64%	52%	12%†
	15-Year Overall Survival‡
	Percent Surviving		Absolute Improvement in Survival with Tamoxifen
	Tamoxifen	No Tamoxifen
Tamoxifen use for 5 years
Overall	64%	56%	8%†

* Combined data from 20 randomized clinical trials that together included 21,457 women

† Statistically significant improvement

‡ Combined data from 44 randomized clinical trials that together included 33,209 women

References

1. Early Breast Cancer Trialists’ Collaborative Group. Effects of chemotherapy and hormonal therapy for early breast cancer on recurrence and 15-year survival: an overview of the randomized trials. Lancet. 365(9472):1687-717, 2005.
2. Davies C, Godwin J, Gray R, et al. for the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: patient-level meta-analysis of randomised trials. Lancet. 378(9793):771-84, 2011.
3. Davies C, Pan H, Godwin J, et al. for the Adjuvant Tamoxifen: Longer Against Shorter (ATLAS) Collaborative Group. Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial. Lancet. 381(9869):805-16, 2013.

Updated 09/11/23