Does Hormone Therapy Cause Breast Cancer?

The Menopause Series · Episode Two · By Wahiba Kartaoui, MSN, FNP-C · Vieora Health

There is a question women lower their voice to ask me. Sometimes they do not ask it at all. They just decide the answer for themselves, quietly, and walk away from care they needed. The question is this. If I take hormones, will I get breast cancer?

I want to answer it the way I wish someone had answered it for me. Plainly, with the real evidence, and without either the fear or the false promises. Because the truth is more hopeful than the headline you were handed, and you deserve to make this decision with the facts, not with a fear that was planted twenty years ago and never corrected.

Almost all of it traces back to one place. In 2002, a large study called the Women's Health Initiative was stopped early, and the news raced around the world in a single frightening sentence. Hormones cause breast cancer. Women threw their prescriptions away. Doctors stopped prescribing. A whole generation of care disappeared in a matter of months.

Here is what did not make the headline. That study looked at one specific combination, an older oral estrogen paired with a synthetic progestin, in women whose average age was sixty three. It was not the whole story. It was one chapter, badly summarized. And in the twenty years since, the researchers have kept following those same women, and the fuller picture that has emerged is very different from the one that frightened your mother.

Let me give you the part almost no one is told.

There are two broad kinds of hormone therapy, and they do not behave the same way. There is estrogen on its own, given to women who no longer have a uterus. And there is combined therapy, estrogen plus a progestogen, given to women who still have theirs, because the progestogen protects the lining of the womb.

Estrogen on its own has not been shown to raise breast cancer risk. In the long follow-up of that very same 2002 study, women who took estrogen alone had about a third fewer breast cancers than the women who took nothing, and they were less likely to die of breast cancer, not more. Read that again, because it is the opposite of what you were taught. For many women, estrogen alone was protective.

Combined therapy, estrogen with a progestogen, is where a small increase in risk shows up. But even here, the story is gentler than the fear. In the same long study, the women on combined therapy had a modest rise in breast cancer diagnoses, and yet they were no more likely to die from breast cancer than the women who took nothing at all. The increase is real, and I will never wave it away. It is also small, and it is not the death sentence the headline implied.

Here is the piece that changes everything, and that older studies could not see, because they only tested one formula.

The small breast cancer signal in combined therapy appears to come from the type of progestogen, not from the estrogen and not from hormones as a category. The old synthetic progestins carry most of the risk. The body identical progesterone we reach for today, the kind that matches what your own body once made, appears to behave very differently.

A large French study that followed tens of thousands of women found that estrogen combined with a synthetic progestin raised breast cancer risk meaningfully, while estrogen combined with body identical progesterone carried essentially no increase in risk at all. Same estrogen. Different partner. A completely different outcome. This is why the formula matters, and why being handed a one size prescription is not the same as being cared for.

Numbers help, because fear grows in the vague. Picture one thousand women in their fifties. A certain number of them will be diagnosed with breast cancer over the coming years no matter what they do, simply because breast cancer is common. Adding estrogen alone changes that count very little, and may even lower it. Adding combined therapy raises it by a small handful of cases over years of use, and the longer the use, the larger the number, which is exactly why we revisit the decision with you over time rather than setting it and forgetting it.

To put that handful of cases in the company it belongs in, the increase from combined therapy sits in the same everyday range as things most of us never think twice about. Drinking a couple of glasses of wine most nights. Carrying extra weight into midlife. These are not offered to frighten you about wine or shame you about weight. They are offered so you can see the true size of this risk, which is small and human sized, not the catastrophe you were sold.

If your main struggle is dryness, discomfort, or the urinary changes so many women endure in silence, there is a low dose estrogen used right where it is needed. It is barely absorbed by the rest of your body, and it has not been linked to breast cancer. It is considered safe to use at essentially any age, for as long as you need it. Many women who are cautious about everything else can still have this relief.

This is the one place I will not hand you a simple answer, because you do not deserve a simple answer, you deserve a careful one. For a woman with a history of breast cancer, systemic hormones are a decision made together with your oncologist, not around them. There are still real options for comfort and quality of life, including nonhormonal treatments and, in selected situations and with your cancer team, local vaginal care. The point is that a breast cancer history does not end the conversation. It changes who sits at the table.

I promised you honesty, so here is the edge of what we know. The research is still moving, especially on how different progestogens compare over the very long term, and no one can hand you a guarantee, in either direction. What I can tell you is that the modern evidence is far more reassuring than the story that scared a generation, that the type of hormone matters enormously, and that this is a decision to be made with a clinician who is actually looking at you, your history, and your risks, rather than reaching for a rule.

At Vieora, we do not read the word hormones and reach for fear, and we do not read it and reach for a sales pitch either. We read you. Your history, your family, your breasts, your risks, your wishes, all of it together. For some women the answer is body identical hormones chosen with care. For some it is a lower dose, a patch, a local option, or a different path altogether. What it is never is a decision made by a headline from 2002.

You were not reckless for wanting to feel like yourself. You are not choosing between your comfort and your life. With the real evidence and the right care, you can very often have both.

If this is the question that has been keeping you from care, let us answer it together, with your own history in front of us.

You can begin with the complimentary quiz, or simply reach out.

With warmth,

Wahiba Kartaoui, MSN, FNP-C

Founder, Vieora Health

Chlebowski RT, et al. Association of menopausal hormone therapy with breast cancer incidence and mortality, long-term follow-up of the WHI trials. JAMA, 2020. link

Fournier A, et al. Unequal risks for breast cancer associated with different hormone replacement therapies, E3N cohort. Breast Cancer Research and Treatment, 2008. link

The Menopause Society. 2022 Hormone Therapy Position Statement. Menopause, 2022. link

American Cancer Society. Menopausal hormone therapy and cancer risk. link

Collaborative Group on Hormonal Factors in Breast Cancer. Type and timing of MHT and breast cancer risk. The Lancet, 2019. link

NICE, UK. Menopause guideline NG23, 2024 update. link

British Menopause Society and Women's Health Concern. HRT and breast cancer risk. link

AUA, SUFU, and AUGS. Genitourinary syndrome of menopause guideline, 2025. link