Updated 2025 — Y-ME National Breast Cancer Organization
Position
Y-ME National Breast Cancer Organization recommends that women fully inform themselves about the individualized risks and benefits of menopausal hormone therapy (MHT) — the term now preferred over the older abbreviation HRT — before making any decision about its use.
The decision to use, continue, or discontinue MHT is deeply personal and should be made collaboratively between a woman and her physician or qualified health care provider, taking into account her individual medical history, menopausal symptom burden, breast cancer risk profile, age, time since menopause, and personal values and preferences.
Y-ME recognizes that for some women, the benefits of MHT — particularly for the management of severe menopausal symptoms — may outweigh the risks. For others, especially those with a personal or strong family history of breast cancer, the risks may be unacceptable. No single recommendation applies to all women.
Background
For much of the late twentieth century, menopausal hormone therapy was widely prescribed to relieve symptoms of menopause — including vasomotor symptoms (hot flashes, night sweats), genitourinary symptoms (vaginal dryness, painful intercourse), sleep disturbance, and mood changes. Physicians also prescribed it with the expectation that it would protect against cardiovascular disease, cognitive decline, and osteoporosis.
Those expectations were largely based on observational studies and anecdotal evidence rather than randomized controlled trials. Beginning in the early 2000s, large-scale clinical trials produced more rigorous — and more complex — findings that fundamentally changed how MHT is prescribed and discussed.
Since our original 2007 position paper, substantial new evidence has emerged from extended follow-up of existing trials, new randomized studies, and updated meta-analyses. This paper incorporates that evidence alongside current guidelines from the North American Menopause Society (NAMS), the American College of Obstetricians and Gynecologists (ACOG), the Endocrine Society, and the National Comprehensive Cancer Network (NCCN).
Types of Menopausal Hormone Therapy
Understanding the research requires clarity about the different forms of MHT, as they carry meaningfully different risk profiles:
- Combined estrogen-progestogen therapy (EPT) — estrogen combined with a synthetic progestogen (progestin), used in women with an intact uterus to prevent endometrial cancer. This form carries the highest documented association with breast cancer risk.
- Estrogen-only therapy (ET) — used in women who have had a hysterectomy. Evidence suggests a more modest breast cancer risk profile than EPT, and in some analyses, no significant increase in risk.
- Micronized progesterone — a body-identical form of progesterone increasingly used in place of synthetic progestins. Emerging evidence suggests it may carry a lower breast cancer risk than synthetic progestogens, though longer-term data are still accumulating.
- Low-dose vaginal estrogen — applied locally to treat genitourinary symptoms. Systemic absorption is minimal, and current evidence does not associate it with increased breast cancer risk. It is considered safe even for many breast cancer survivors, per NAMS 2023 guidance.
- Tissue-selective estrogen complex (TSEC) — a newer combination approach pairing estrogen with a selective estrogen receptor modulator (SERM), such as the conjugated estrogen/bazedoxifene combination (Duavee/Duavive).
Research and Evidence
The Women’s Health Initiative (WHI) — Original Findings and Subsequent Reassessment
The Women’s Health Initiative (WHI), launched in 1991 and reporting initial findings in 2002, remains the largest randomized controlled trial of MHT ever conducted. Its findings — demonstrating small but statistically significant increases in breast cancer, cardiovascular events, stroke, and pulmonary embolism with combined EPT — led to a dramatic global decline in hormone therapy prescribing.
However, subsequent reanalysis and extended follow-up of WHI data have led to an important reassessment of those findings:
- The original trial enrolled predominantly older postmenopausal women (average age 63), many of whom were well past the typical window of menopause onset. The risks identified may not apply equally to younger women (aged 50–59, or within 10 years of menopause), who represent the primary population now considered for MHT.
- The “timing hypothesis” — sometimes called the window of opportunity — has been supported by subsequent analyses: women who initiate MHT close to the onset of menopause appear to have a more favorable cardiovascular and overall risk-benefit profile than those who begin therapy many years later.
- The estrogen-only arm of the WHI (in women post-hysterectomy) found no statistically significant increase in breast cancer risk and in some analyses suggested a possible reduced risk — a finding confirmed in 18-year follow-up data published in JAMA (Manson et al., 2017).
- 18-year cumulative follow-up (Manson et al., 2017, JAMA) found that the absolute risks associated with both EPT and ET were small, and that for women who initiated therapy in their 50s, overall mortality was not significantly increased.
The Million Women Study — Updated Context
The Million Women Study (Beral et al., 2003, Lancet), an observational study of over one million UK women aged 50–64, found that women using combined EPT had approximately double the risk of breast cancer compared to non-users, and that estrogen-only users also had elevated risk. These findings were influential but have since been noted to have observational limitations, including potential confounding and the lack of randomization.
The CECILE, E3N, and EPIC Studies — Progestogen Type Matters
European cohort studies have contributed critical nuance regarding progestogen type:
- The French E3N cohort study (Fournier et al., 2008, updated 2014) found that combined therapy using micronized progesterone or dydrogesterone was associated with significantly lower breast cancer risk than regimens using synthetic progestins such as medroxyprogesterone acetate (MPA) — the progestin used in the WHI.
- These findings suggest that the elevated breast cancer risk historically associated with EPT may be partly driven by the type of progestogen used, not estrogen-progestogen combination therapy as a uniform category.
- This distinction has influenced European prescribing practices and is increasingly acknowledged in North American guidelines, though randomized trial confirmation is still pending.
The KEEPS and ELITE Trials — Timing of Initiation
- The Kronos Early Estrogen Prevention Study (KEEPS) (Harman et al., 2014) found no significant cardiovascular harm — and some cognitive benefit — when MHT was initiated in recently menopausal women aged 42–58.
- The Early versus Late Intervention Trial with Estradiol (ELITE) (Hodis et al., 2016, NEJM) demonstrated that timing of initiation significantly affected atherosclerosis progression — women who began estradiol within 6 years of menopause had slower progression of subclinical atherosclerosis compared to those who began therapy more than 10 years after menopause.
- These trials support the concept that initiating MHT early in the menopausal transition, before cardiovascular pathology is established, may carry a more favorable risk profile.
Breast Cancer Risk — Current Summary of Evidence
Based on the totality of current evidence:
- Combined EPT with synthetic progestins is associated with a modest increase in breast cancer risk, particularly with use beyond 3–5 years. The absolute risk increase for an individual woman is small but real.
- Estrogen-only therapy in women post-hysterectomy does not appear to significantly increase breast cancer risk and may, in some analyses, be associated with a modest risk reduction — particularly for ER-negative breast cancer.
- Micronized progesterone-based regimens may carry lower breast cancer risk than synthetic progestin regimens, though this requires confirmation from randomized trial data.
- Duration of use matters: risk appears to increase with longer duration of combined EPT use and decreases after discontinuation, though some residual risk may persist.
- Women with a personal history of breast cancer are generally advised to avoid systemic MHT, particularly hormone receptor-positive breast cancer survivors. Low-dose vaginal estrogen for genitourinary symptoms is considered on a case-by-case basis.
- Women carrying BRCA1 or BRCA2 mutations who undergo risk-reducing salpingo-oophorectomy (RRSO) before natural menopause face the question of MHT in a different context — current evidence does not suggest that short-term MHT use in this group significantly increases breast cancer risk above their baseline, and NCCN guidelines acknowledge its use in this population, though individualized discussion is essential.
The HRT-Breast Cancer Incidence Connection
Following the publication of WHI findings in 2002 and the resulting sharp decline in MHT prescribing, breast cancer incidence rates in postmenopausal women fell significantly between 2002 and 2004 — an observation first noted by Ravdin et al. (2007, NEJM) and Clarke and Glaser (2006). This population-level observation further supported a causal relationship between combined MHT use and breast cancer incidence. More recent surveillance data has continued to be monitored in this context.
Current Clinical Guidelines (2023–2024)
North American Menopause Society (NAMS) — 2022 Hormone Therapy Position Statement
The NAMS 2022 Position Statement concludes that for healthy women under age 60, or within 10 years of menopause onset, the benefits of MHT outweigh the risks for treatment of bothersome vasomotor symptoms and for prevention of bone loss. NAMS explicitly states that “the risks of hormone therapy differ by type, dose, duration of use, route of administration, timing of initiation, and whether a progestogen is used.”
American College of Obstetricians and Gynecologists (ACOG)
ACOG affirms that MHT remains the most effective treatment for menopausal vasomotor symptoms and is appropriate for women without contraindications. ACOG emphasizes shared decision-making and individualized risk assessment, and notes that the blanket avoidance of MHT prompted by early WHI reporting was not warranted for all women.
Endocrine Society
The Endocrine Society supports MHT use for symptomatic women younger than 60 or within 10 years of menopause, with the lowest effective dose for the shortest necessary duration. For women over 60 or more than 10 years post-menopause, a more conservative approach is advised given the less favorable cardiovascular risk-benefit profile.
NCCN — Breast Cancer Risk Reduction Guidelines (2024)
NCCN advises that women with a personal history of breast cancer should generally avoid systemic MHT. For high-risk women without a cancer history, the decision involves weighing menopausal symptom burden against individual cancer risk factors and should be made with full informed consent.
Non-Hormonal and Alternative Options
For women who cannot or choose not to use MHT, effective non-hormonal alternatives exist for managing menopausal symptoms and should be discussed with a physician:
- Vasomotor symptoms: Fezolinetant (Veozah) — an FDA-approved non-hormonal neurokinin B receptor antagonist — received approval in 2023 as the first non-hormonal prescription treatment specifically for moderate-to-severe hot flashes. SSRIs and SNRIs (paroxetine, venlafaxine, escitalopram), gabapentin, and clonidine have also demonstrated efficacy.
- Genitourinary symptoms: Low-dose vaginal estrogen, ospemifene (an oral SERM), vaginal DHEA (prasterone), and non-hormonal vaginal moisturizers and lubricants.
- Bone health: Bisphosphonates, denosumab, raloxifene, and romosozumab depending on fracture risk profile.
- Lifestyle interventions: Regular weight-bearing exercise, adequate calcium and vitamin D intake, smoking cessation, and limiting alcohol all support bone and cardiovascular health during and after the menopausal transition.
Summary
The evidence on menopausal hormone therapy has evolved substantially since Y-ME’s original 2007 position paper. The picture is now considerably more nuanced than early post-WHI messaging suggested:
- MHT remains the most effective treatment for moderate-to-severe menopausal vasomotor symptoms.
- Timing, type, dose, route, and duration of MHT all influence the risk-benefit calculation.
- Combined EPT with synthetic progestins carries the clearest documented breast cancer risk; estrogen-only therapy carries less risk; micronized progesterone regimens may carry less risk still.
- For healthy women under 60 and within 10 years of menopause, current major guidelines support individualized use of MHT when symptoms significantly affect quality of life.
- Women with a personal history of breast cancer, particularly hormone receptor-positive disease, should generally avoid systemic MHT and explore non-hormonal alternatives.
- Non-hormonal options — including the newly approved fezolinetant — have expanded meaningfully and should be discussed as part of a comprehensive menopause management plan.
Y-ME encourages every woman approaching or experiencing menopause to have a thorough, individualized conversation with her health care provider — one that takes into account her complete medical history, her symptom burden, her cancer risk profile, and her personal values. Informed, empowered decision-making is at the core of everything Y-ME stands for.
References
Beral, V., & Million Women Study Collaborators. (2003). Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet, 362(9382), 419–427.
Chlebowski, R. T., Anderson, G. L., Aragaki, A. K., et al. (2020). Association of menopausal hormone therapy with breast cancer incidence and mortality during long-term follow-up of the Women’s Health Initiative randomized clinical trials. JAMA, 324(4), 369–380.
Fournier, A., Fabre, A., Mesrine, S., Boutron-Ruault, M. C., Berrino, F., & Clavel-Chapelon, F. (2008). Use of different postmenopausal hormone therapies and risk of histology- and hormone receptor-defined invasive breast cancer. Journal of Clinical Oncology, 26(8), 1260–1268.
Harman, S. M., Black, D. M., Naftolin, F., et al. (2014). Arterial imaging outcomes and cardiovascular risk factors in recently menopausal women: A randomized trial. Annals of Internal Medicine, 161(4), 249–260.
Hodis, H. N., Mack, W. J., Henderson, V. W., et al. (2016). Vascular effects of early versus late postmenopausal treatment with estradiol. New England Journal of Medicine, 374(13), 1221–1231.
Manson, J. E., Aragaki, A. K., Rossouw, J. E., et al. (2017). Menopausal hormone therapy and long-term all-cause and cause-specific mortality: The Women’s Health Initiative randomized trials. JAMA, 318(10), 927–938.
North American Menopause Society. (2022). The 2022 hormone therapy position statement of The Menopause Society. Menopause, 29(7), 767–794.
Rossouw, J. E., Anderson, G. L., Prentice, R. L., et al. (2002). 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), 321–333.
Simon, J. A., & Reape, K. Z. (2023). Fezolinetant for the treatment of vasomotor symptoms associated with menopause. Expert Opinion on Pharmacotherapy, 24(14), 1555–1565.
Vinogradova, Y., Coupland, C., & Hippisley-Cox, J. (2020). Use of hormone replacement therapy and risk of breast cancer: Nested case-control studies using the QResearch and CPRD databases. BMJ, 371, m3873.
Women’s Health Initiative. (2002). Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA, 288(3), 321–333.
For breast cancer information or peer support, contact the Y-ME National Breast Cancer Organization Hotline at 1-800-221-2141 (available 24 hours a day, 7 days a week) or 1-800-986-9505 (Spanish).
This position paper is intended for informational purposes and does not constitute medical advice. Please consult a qualified health care provider for guidance specific to your individual circumstances.
