This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: Menopausal hormone therapy (MHT) increases the risk of developing breast cancer (see Table 8) . For this reason, women are advised to avoid long-term use of MHT. MHT is also known as postmenopausal hormone therapy and hormone replacement therapy.
MHT is usually not given to breast cancer survivors because findings from large randomized controlled trials have shown MHT use increases the risk of [2-3]:
Women have other options for treating menopausal symptoms (learn more).
Learn about the strengths and weaknesses of different types of studies.
Study selection criteria: Randomized controlled trials.
Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Relative Risk of a Breast Cancer Event Among Survivors Who Used MHT after Breast Cancer Compared to Those Who Did Not, RR (95% CI)
Randomized controlled trials
Holmberg et al. 
Local recurrence, metastasis orcancer in the opposite breast:2.2 (1.0-5.1)
Fahlén et al. 
Local recurrence:0.8 (0.3-1.7)
Cancer in the opposite breast:3.3 (1.2-10.9)
1. Writing Group for the Women’s Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA. 288(3):321-33, 2002.
2. Holmberg L, Iverson OE, Rudenstam CM, et al., for the HABITS Study Group. Increased risk of recurrence after hormone replacement therapy in breast cancer survivors. J Natl Cancer Inst. 100(7):475-82, 2008.
3. Fahlén M, Fornander T, Johansson H, et al. Hormone replacement therapy after breast cancer: 10 year follow up of the Stockholm randomised trial. Eur J Cancer. 49(1):52-9, 2013.
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