Hormones & Cancer

Hormones & Cancer

Hormones & Cancerpatient education blog image
by Worldlink Medical
July 22, 2020

Since the WHI trial ended in 2002, hormones and cancer have become synonymous in many healthcare circles. Women, wrestling with menopausal symptoms and aging indicators, are often left with zero alternatives as doctors have pulled the therapy from their prescribing repertoire. This has left many women lodged  between a rock and a hard place wondering, “Should I take hormones for other health benefits and risk a slight possibility of breast cancer, or go without and suffer from hot flashes, osteoporosis, emotional upheaval, and cognitive decline?”

In this article we’ll discuss cancer and hormones. If you’re interested in an in-depth discussion on the WHI trial, please read our post called The Whys of the WHI Trial.

To find a doctor near you, simply search the Bio-Identical Hormone Therapy (BHRT) Provider Directory.

Why the WHI Trial Showed an Increased Breast Cancer Risk: Age and Hormones Matter

The WHI trial, a randomized clinical study of more than 10,000 women ages 50 to 79, looked at whether taking Premarin, either alone or with a progestin, continuously after menopause could help women prevent heart disease, stroke, and cognitive decline.

WHI researchers found that women who took the combination of estrogen and progestin had an increased risk of coronary heart disease, stroke, deep vein thrombosis and breast cancer.

This risk of breast cancer, heart disease and other conditions varied depending on the women’s age when she started the therapy and whether she took progestin along with the estrogen.


Progestins are frequently prescribed for contraception or during postmenopausal hormone replacement therapy as a means to block estrogen-induced endometrial growth. These “synthetic” hormones have been linked to a higher incidence of breast cancer and negative cardiovascular outcomes.


Only 30% of the study participants were aged 50 to 59, the years in which most women undergo hormone replacement therapy. The rest of the women were older and outside the normal period women should begin treatment with some having pre-existing comorbidities prior to participating in the study.

Both progestin and age factored into the negative outcomes seen in the study.

What Studies Have Shown Regarding Bio-Identical Hormones and Breast Cancer

Evidence to date does not indicate that bio-identical progesterone increases the risk of breast cancer and several studies have indicated that it actually protects breast tissue. A French study of 1,150 women with fibrocystic breasts saw no increased breast cancer risk in women using topical progesterone. On top of this, the study also showed that breast cancer risk decreased significantly when topical progesterone was combined with oral progesterone (RR = 0.5 compared to nonusers).

The largest study to date that most conclusively addresses the debate over progesterone and breast cancer is the French E3N-EPIC (European prospective investigation into cancer and nutrition) which is a cohort study looking at over 50,000 women. It showed the same results as the WHI in women using synthetic progestins, that is a 26% increased risk for invasive breast cancer. However, it showed a 10% decreased risk for breast cancer in women using progesterone.

Another study found breast cancer patients with the highest endogenous progesterone levels at the time of surgery had significantly better survival at 18 years follow-up.

In an observational study, a decreased risk of histology- and hormone receptor–defined invasive breast cancer was noted with use of a combination of micronized progesterone and estrogen vs the use of synthetic progestogens

Finally, a Belgian study revealed that the administration of progesterone decreased the breast proliferation induced by estradiol, which suggests a role for progesterone even in women who do not have an intact uterus.

Over and over, we see that the type of hormone used has the biggest impact on how the body responds to hormone replacement therapy. It’s not a matter of “should you” but “what you” put in your body to combat menopause and the subsequent decline in systems in the female body.

Why We Must Keep a Level Head

The short-term and long-term benefits of hormone replacement are difficult to overstate. The alarmist reporting on the WHI destroyed years and years of clinical and laboratory evidence supporting hormone therapy and left countless women to suffer through menopause and the many negative effects associated with a lack of hormones.

The good news regarding the WHI is over the years, level heads have prevailed and more research has revealed that all risks initially found are minimal (even with the synthetic hormones). It turns out that the exaggerated headlines over the initial results were much ado about nothing. In fact, a 2017 JAMA investigation showed that among postmenopausal women, hormone therapy with CEE plus MPA for a median of 5.6 years or with CEE alone for a median of 7.2 years was not associated with risk of all-cause, cardiovascular, or cancer mortality during a cumulative follow-up of 18 years.

Ultimately, the best outcome of the results from the WHI is that they shone a light on bio-identical alternatives that have better health outcomes and less risks overall. Women are now presented with more choices and healthier approaches than ever before.

To find a doctor near you, simply search the Bio-Identical Hormone Therapy (BHRT) Provider Directory.


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Desreux J, Kebers F, Noël A, et al. Progesterone receptor activation: an alternative to SERMs in breast cancer. Eur J Cancer. 2000;36(supp 4): 90-91.

Fournier A, Fabre A, Mesrine S, Boutron-Ruault MC, Berrino F, Clavel-Chapelon F. Use of different postmenopausal hormone therapies and risk of histology- and hormone receptor-defined invasive breast cancer. J Clin Oncol. 2008;26:1260-1268.

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Crandall CJ, Hovey KM, Andrews CA, Chlebowski RT, Stefanick ML, Lane DS, Shifren J, Chen C, Kaunitz AM, Cauley JA, Manson JE. Breast cancer, endometrial cancer, and cardiovascular events in participants who used vaginal estrogen in the WHI Observational Study. Menopause. 2018 Jan;25(1):11-20.

Manson JE, Aragaki AK, Rossouw JE, et al. Menopausal Hormone Therapy and Long-term All-Cause and Cause-Specific Mortality: The Women’s Health Initiative Randomized Trials. JAMA. 2017;318(10):927–938.