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Hormone positive breast cancer

Hormone positive breast cancer: the definition, typical antihormone treatment, and management of possible unwanted common side effects

When diagnosed with breast cancer, it is instant information overload. This is especially true when your surgeon or oncologist reviews your biopsy pathology report. This is when you learn the type of breast cancer, the stage, and the typical course of treatment. You may have heard the words “You have hormone-positive” breast cancer, as it is the most common type. If you were confused at the thought of your hormones causing cancer, you are not alone. Let me try to explain! There are targeted treatments for hormone positive cancer, and while they do an excellent job at preventing reoccurrence, they are often accompanied by unwanted side effects. Luckily, there are therapeutic solutions that can make treatment much more tolerable!

Hormone-positive breast cancer

The two hormones I’m referring to are estrogen and progesterone, which go hand in hand. Estrogen affects both male and female development. It has many other important responsibilities, but we will focus on its role in reproductive and breast health. The most important job of progesterone is in the menstrual cycle and in growing a baby. The two hormones act like messengers within the body that influence other cells and tissues. We will be focusing on the effect of estrogen-driven breast cancer.

While much of estrogen’s role in breast and other cancers is still not fully understood, we do know it disrupts normal healthy cell division. Estrogen can attach to a cell and send a message to create more cells, causing rapid division and growth. This is beneficial in pregnancy, for example. Where you don’t want to see rapid division and growth is in cancer cells, which is exactly what it does in hormone-positive breast cancer.

If you’re post-menopausal, you might be wondering how your body had enough estrogen to cause this, since estrogen drops significantly after menstruation has ceased. The answer is that the body is always trying to make estrogen! When you’re premenopausal (still having a menstrual cycle) female ovaries do most of the work in producing the hormone. When you’re postmenopausal, estrogen is created through adipose (fat) cells. This is also why obesity is an increased risk factor for breast cancer.

Now that we have a little 101 on estrogen, let’s briefly talk about the types of breast cancer and the hormonal effect.

Types of breast cancer

Breast cancer can be invasive or noninvasive. Invasive breast cancer is the most common type. Invasive means that breast cancer has spread into the surrounding breast tissue. This includes invasive ductal carcinoma (80% of all breast cancer), invasive lobular carcinoma, inflammatory breast cancer, and metastatic breast cancer. There are several other less common subtypes as well. Invasive breast cancer is considered stages 1 through 4. Noninvasive breast cancer is called ductal carcinoma in situ (DCIS) which is stage 0 breast cancer. In this case, breast cancer has never left the duct and has not spread to other breast tissue. Both invasive and noninvasive breast cancer have cell receptors that tell if the cancer was fueled by estrogen and progesterone (referred to as ER and PR on your pathology report).

A protein called human epidermal growth factor receptor 2 (HER2) is the third important component in a pathology report; it is pertinent in treating invasive breast cancer which is why you will not see it in your report If you have DCIS.

To summarize, both invasive and noninvasive breast cancer may or may not be fueled by hormones. Since hormones cause most breast cancer, we will focus on the typical treatment for such and the management of common side effects. Treatment refers to the oral medication taken after surgery, radiation, and chemotherapy if necessary. When taken after surgery, it’s referred to as “adjuvant therapy.” If the medication is taken before surgery (less common) it is referred to as “neoadjuvant therapy”. If breast cancer is ER and PR negative, antihormone therapy is not an option because hormones did not contribute to the growth of that cancer.

Typical anti-hormone treatment

Oncologists use anti-hormone therapy (also referred to as endocrine therapy or simply hormone therapy) to slow the growth of hormone-positive tumors by either blocking the body from producing hormones or disrupting the effects of hormones on breast cancer cells. They are typically taken once a day, for 5-10 years.

Note: To clear any confusion, this is not the same therapy where women take estrogen or progesterone to combat menopausal symptoms such as hot flashes, mood swings, or insomnia. The use of those medications with hormone-positive breast cancer is typically contraindicated.

There is a class of drugs called aromatase inhibitors that decrease estrogen throughout the body. These drugs block an enzyme called aromatase found in fatty tissue that converts hormones into estrogen. Examples include Anastrazole (Arimidex), Letrozole (Femara), and Exemestane (Aromasin).

Another category of anti-estrogen drugs referred to as selective estrogen receptor modulators (SERMS) block estrogen from attaching to cancer cells therefore inhibiting the ability to grow and divide. These include Tamoxifen (Nolvadex), and Toremifene (Fareston).

The other common drug is Fulvestrant (Falsodex) which works slightly differently to block estrogen.

Common side effects and measures for relief

Depending on their mechanism of action, these drugs each have individual potential side effects. Some of which are more severe and adverse such as blood clots or stroke and your provider will determine if you are an appropriate candidate. We will focus on the most common side effects and simple therapeutic measures that may provide some relief.

Hot flashes and night sweats: By lowering estrogen in the body, your body’s hormones are disrupted and can cause sudden changes in body temperature. It can be embarrassing and irritating. Many women, regardless of a breast cancer diagnosis, will experience this at some point in their lives due to going through menopause. Wear moisture-wicking clothes during the day and in the evening. Running shirts, shorts, and undergarments are great for this. Some women have noticed a decrease in hot flashes after trying acupuncture. And while some studies suggest it may be more of a placebo effect, an improvement in symptoms is a win! Dr. Liz O’Riordan, breast surgeon and breast cancer survivor, claims that using separate duvets in bed from your partner is a game changer. Using a lighter duvet still allows the comfort of a weighted blanket without the heaviness that inevitably will have you waking up in a sweat. Dr. Riordan is an excellent educational source to follow on social media (oriordanliz on Instagram or There are also a few medications that can be prescribed for hot flashes that you can talk to your oncologist about.

Weight gain: While the relationship between weight gain and hormone therapy is not completely understood, physical inactivity and nausea while on the medications may contribute. For healthy weight loss, consider a predominantly whole foods plant-based diet. This means increasing your fruits and vegetables (especially cruciferous vegetables- broccoli, kale, brussels sprouts, etc.), decreasing red meat and other saturated fats like butter, oil dairy, and eating more whole grains and legumes. Choose leaner proteins like chicken or fish and avoid processed meats. Your plate should reflect the colors of a rainbow, a diet that’s rich in diversity. This way of eating encourages an anti-inflammatory approach, which is also cancer-fighting. It helps to look at it as a lifestyle, and not a diet. Find inspiration through searching “anti-inflammatory diet” online, or “plant-based” recipes.

Continue to be as active as you can to help promote weight loss along with healthy eating.

Joint pain: Joint pain is probably the most common side effect of antihormone therapy. This can include pain even in the wrists, fingers, and toes. It’s typically worse first thing in the morning and improves as the day goes on. This is likely because the more active the body, the more movement within the synovial fluid between joints. Consistent movement is important. If your job is sedentary, standing and walking every hour will help prevent joint stiffness. For the most improvement, daily physical activity as well as an anti-inflammatory diet as noted above is recommended. Water aerobics, swimming, and cycling are great activities if you need low impact. Moist heat in the form of a heating pad, bathing with Epsom salts, or sauna therapy for a short period if you are medically permitted. Some supplements may be beneficial such as glucosamine, Omega 3s, or turmeric. Tylenol or anti-inflammatories (taken with food) may be helpful but always discuss with your doctors, especially your oncologist, before taking to avoid any harmful interactions. Alcohol is also inflammatory.

These symptoms may improve over time or may last throughout your treatment. You can also try switching therapies under the guidance of your oncologist if one is simply not tolerable. It is usually trial and error figuring out what makes you feel better. Sometimes just finding a support group locally or online and knowing that you are not going through these symptoms alone is a great start. And remember, be honest about how you are feeling with your providers. They want you to receive the most beneficial treatment, but your quality of life is equally as important!


Okumatsu K, Yamauchi H, Kotake R, Gosho M, Nakata Y. Association between Endocrine Therapy and Weight Gain after Breast Cancer Diagnosis among Japanese Patients: A Retrospective Cohort Study. Medical Sciences. 2021;9(3):50.

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About the Author
Dr. Lauren Mackie, DNP, FNP-C is a freelance medical writer, specializing in breast health. She is also a doctoral-prepared family nurse practitioner in oncologic breast surgery. She can be reached at for inquiries. Opinions are her own, and should not be a substitute for professional medical advice.

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