If you have been diagnosed with hormone receptor positive breast cancer, meaning that the cancer cells were shown to be fueled by estrogen, and sometimes progesterone, no doubt as part of your post-surgery treatment plan, your doctor recommended that you take hormone inhibiting drugs. You would have been recommended to take either Tamoxifen, which blocks the action of estrogen and is normally offered to premenopausal women, or an aromatase inhibitor like Femara, Arimidex, Aromasin or Evista, which block the production of estrogen, and are normally offered to postmenopausal women.

You probably then went to the Internet, had a look at the side effects of these drugs, and got worried. It seems that taking them for five years was hard enough – so what are the merits or pitfalls of taking them for ten years?

For Tamoxifen, a study released In 2012 [1] found that extending treatment with Tamoxifen from five years to ten years reduced both recurrence of and death from breast cancer. Because of this study, many women have been recommended to continue on with Tamoxifen for ten years rather than five.

For those taking aromatase inhibitors, however, many wondered if the findings about Tamoxifen could be extrapolated to aromatase inhibitors. A study published in 2016 [2] in the New England Journal of Medicine investigated whether or not extending the taking of the aromatase inhibitor letrozole (Femara) from five to ten years for women with hormone receptor positive breast cancer would be beneficial.

1,918 postmenopausal women were enrolled in the trial and half of them were assigned to either take letrozole for five additional years (after already taking it for five years), the other half were given a placebo. 959 women were treated with letrozole for ten years and compared with 959 women who took letrozole for five years and a placebo for five years. On average, the participants were followed for just over six years so that researchers could examine their recurrence rates in the same breast, or a new breast cancer diagnosis in the opposite breast. They also looked at overall survival and quality of life.

Researchers found that although there was a “statistically significant” improvement in disease-free survival (women experiencing neither a recurrence in the same breast nor a new diagnosis in the other breast), for women taking the letrozole there was no difference in actual survival at the five year mark. So in effect this means that 91% of women who did not take the letrozole for the additional five years were disease-free five years later and 94% of women who did take letrozole for an additional five years were disease-free five years later. That’s a difference of 3% between the two groups, with no difference in overall survival. The study was partly funded by Novartis, the maker of letrozole.

Those Pesky Side Effects

The problem is that there are significant side effects from hormone blocking medications. The side effects and toxicity of Tamoxifen and the aromatase inhibitors are rather different, but each definitely has a significant impact on health and quality of life for a large percentage of the women who take these drugs.

In my experience as a health coach, a small percentage of women tolerate these treatments fairly well, but for most, these drugs come with fairly severe side effects. Many women stop the medication before completing the recommended course due to life-altering side effects. What are some of the most common side effects? Here’s a partial list:

• joint pain and stiffness, feelings of being far older than you actually are
• muscle pain and weakness, leg cramps
• bone pain, bone fractures, higher risk for osteoporosis
• hot flashes and night sweats
• headaches
• dizziness
• vaginal dryness and loss of libido
• uterine lining abnormalities, and a higher risk for needing hysterectomy
• tiredness, fatigue, lethargy
• anxiety, depression (sometimes severe)
• vision changes, dry eyes, damage to cornea and retina
• insomnia
• weight gain
• loss of mental acuity and brain fog
• hair thinning
• blood clots and pulmonary embolisms
• fatty liver

I believe that any treatment which fails to significantly improve overall survival while at the same time exposing women to that many serious side effects should be considered very carefully. It’s also important to know that the World Health Organization considers Tamoxifen to be a human carcinogen.

I believe we need our estrogen, keeping it in balance is the key. Many women are not even checked to see what their estrogen levels are after surgery, chemotherapy and radiation have taken their toll – they are just told that blocking the action of estrogen is imperative and they “need” to take these drugs to improve their chance of survival.

The Many Functions of Estrogen

Besides its functions in reproductive health, which can be found in any book on the subject, here’s what our body’s own estrogen also does for us [3]:

• helps maintain body temperature
• involved in energy production in the body including muscles
• enhances the effects of certain neurotransmitters, the brain’s “feel-good” chemicals, so intimately involved in mood regulation
• improves the thickness and quality of skin, as well as collagen content
• alters disposition of fat cells around abdomen
• helps to preserve bone strength
• prevents bone loss
• promotes pancreatic health and regulates insulin secretion
• regulates cholesterol production in the liver, so has cardioprotective properties
• maintains vaginal health
• affects vascular tone and blood flow in organs and tissues, including the eyes
• protective to brain and nervous system

The Role of Xenoestrogens in Hormone Receptor Positive Breast Cancer

I believe that xenoestrogens (environmental estrogens, known hormone disrupters) are much more dangerous to our health than our body’s own estrogen, and I’m not alone. In the book “Molecules of Emotion“, author and scientist Candace Pert stated “… accumulated environmental pollutants within our bodies are mimicking and disrupting the action of our sex hormones — estrogen, progesterone, and testosterone — which run the male and female reproductive systems.” She continues with this line of thought, stating “A recent report on receptor binding in Science, for example, has shown that environmental toxins have estrogenlike effects and bind to estrogen receptors, where they can stimulate breast cancer tumor growth. Similarly, various toxins can act like testosterone in the male body and stimulate prostate cancer, which is embryologically similar to breast cancer. Although this has been suspected for a long time, only recently have we gotten the hard proof that accumulation of these toxins in our bodies chronically stimulates our estrogen and testosterone receptors, putting them into a state of overdrive and leading to cancer.”

Dr Pert is not alone in these thoughts. Countless others have seen the problems associated with xenoestrogens on hormonal health. It is my belief that we need to start there – by detoxifying our food, our body products, our household cleaning supplies, etc. See my article for more information.

Bottom Line: Please evaluate the potential benefits and harms of hormone blocking medications, and talk to your health care provider about your concerns. Please be aware that estrogen is not the only factor involved in breast cancer. For a tumor to begin growing, and to be allowed to continue to grow, a good many things have to go wrong first. A good overall anti-cancer strategy would be to eat a healthy diet full of fresh organic fruits and vegetables, include particular super foods, take supplements that have research backing them (see my page discussing that), detox your household from toxic skin care, hair care and household cleaning products, get plenty of exercise every day, and keep your stress levels down. If you’d like my help putting together a personalized program, I’d be happy to assist you. You might like to consider my coaching services.


[1] 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 – https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)61963-1/fulltext

[2] Extending Aromatase-Inhibitor Adjuvant Therapy to 10 Years – https://www.nejm.org/doi/full/10.1056/NEJMoa1604700

[3] The Role of Estrogens in Control of Energy Balance and Glucose Homeostasis – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3660717/

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