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Hormone Therapy for Breast Cancer

Hormone Therapy for Breast Cancer

Breast cancer hormone therapy treatment is often used to treat breast cancer that is affected by hormones such as estrogen and progesterone. Breast cancer treatment options can change depending on several factors such as stage of disease, subtype, previous therapies, hormone receptor status, and more. On breast cancer cells there are receptors that attach to these hormones, which causes them to grow. Hormone therapy for breast cancer prevents the hormones from helping the breast cancer cells grow. 

What Does Hormone Therapy Do for Breast Cancer?

Nearly two thirds of all breast cancer cases are hormone receptor-positive, meaning they have hormones helping breast cancer cells reproduce and grow. Hormone receptor-positive cancer cells are likely to respond to hormone therapy. By blocking the cancer cells from being attached with hormones, it blocks the spread and development of cancer. Hormone therapy for breast cancer is also used in cases that spread throughout the body, or cancer that returns after treatment. Hormone therapy is often combined with another treatment method, usually surgery. 

Adjuvant Hormonal Therapy for Breast Cancer

Hormone therapy is utilized after surgery, which aids in reducing the risk for recurrence of the cancer. Unlike many other types of treatment, hormone therapy is typically given for 5 years, and in some cases longer. 

This therapy is either given as an oral medication or hormone injections for breast cancer treatment. In most cases, hormone therapy is used as an adjuvant therapy, but in some cases, it is started prior to surgery as a neoadjuvant therapy. 

What Types of Hormone Therapy are Used for Breast Cancer?

The types of hormone therapy for breast cancer are different in how they stop hormones from attaching to cancer cell receptors and what type of hormones they target. Breast Cancer Hormone Therapy Drugs that block estrogen receptors from driving cell growth include: 

  • Tamoxifen 
  • Fulvestrant (Faslodex) 
  • Toremifene (Fareston) 

There are also Aromatase inhibitors (AIs), which are anti hormone pills that lower the estrogen levels in the body by preventing aromatase from making estrogen. Essentially, it is medicine to medicine to block estrogen, which is helping the cancer grow. These medications are taken orally and include: 

  • Exemestane (Aromasin) 
  • Anastrozole (Arimidex) 
  • Letrozole (Femara) 

For pre-menopausal women, preventing the ovaries from functioning properly reduces estrogen levels from the body’s main source. Suppression of the ovaries often causes symptoms like menopause, which may include hot flashes, mood swings, night sweats, and vaginal dryness. There are three ways to suppress the ovaries for treating breast cancer: 

  • Oophorectomy: Surgical procedure to entirely remove the ovaries and prevent any future production of estrogen. 
  • Chemotherapy drugs: Chemotherapy drugs are known to damage the ovaries and prevent production of estrogen. This damage to estrogen production can be temporary in some patients for months or years. In some women, the ovaries will be permanently damaged and will lead to menopause. 
  • Luteinizing hormone-releasing hormone (LHRH) agonists: The most common method of ovarian suppression, these drugs halt the signals sent to the ovaries to make estrogen. This leads to temporary menopause. These drugs include goserelin (Zoladex) and leuprolide (Lupron), which are sometimes used with other hormone drugs. 

While there are a variety of anti-estrogen medication names, above are the most commonly used. 

Hormone Therapy for Breast Cancer Pros and Cons 

Hormone therapy for breast cancer pros and cons depend on which type of hormone therapy is given.  There are pros and cons for many cancer treatments, and it is best to talk to your doctor about weighing the risks of all available treatment options. The most widely known benefit for hormone therapy is limiting the chance of the cancer returning after treatment is completed. There is always a risk of reoccurrence even after hormone therapy but reducing that risk can help give patients some peace of mind. However, there are still complications that patients can occur throughout treatment. For pre-menopausal women, hormone therapy will at least temporarily affect the hormone production in the body. Many women are still fertile and start their periods again after hormone therapy is complete. However, in some cases, women are no longer fertile and will not get their periods after treatment. Refusing hormone therapy for breast cancer is an option all patients have, but it is best to discuss any concerns with your doctor regarding hormone therapy and breast cancer risk. For the different hormone therapy drugs, there are some similar side effects across the drugs, but there are also several key differences.  

Fulvestrant, a drug used as hormone therapy for breast cancer side effects often include: 

  • Hot flashes or night sweats 
  • Headache 
  • nausea 
  • Bone pain 
  • Injection site pain 

The most common side effects of tamoxifen and toremifene seen in patients include: 

  • Hot flashes 
  • Vaginal dryness or discharge 
  • Changes in the menstrual cycle 
  • Tumor flare, which temporarily increases the size of a tumor 

Some common side effects of AIs are: 

  • Hot flashes 
  • Vaginal dryness 
  • Bone and joint pain 
  • Muscle pain 

There are additional side effects seen in patients that are more serious, but do not occur nearly as often as those listed above. Most women experience minor symptoms such as hot flashes and breast tenderness with hormone replacement therapy, but it is important to be aware of all the risks. They are listed below by drug:  


  • Nausea, vomiting, or constipation 
  • Headache 
  • Hot flashes 
  • Fatigue 
  • Loss of appetite 
  • Pain in the bones, back, muscles, and joints   
  • Shortness of breath,  
  • Persistent cough 


  • Risk of blood clots, especially in the legs or lungs 
  • Stroke (extremely rare) 

Tamoxifen and Toremifene 

  • Risk of blood clots, especially in the lungs and legs 
  • Stroke 
  • Cataracts 
  • Endometrial cancer and uterine sarcoma 
  • Bone loss in premenopausal women 
  • Mood swings and loss of libido 
  • Headaches, nausea, vomiting, skin rash, impotence, and loss of libido (In men) 

Ovarian suppression 

  • Bone loss 
  • Mood swings 
  • Loss of libido 
  • Depression  

Aromatase inhibitors 

  • Risk of heart attack, heart failure, and hypercholesterolemia 
  • Bone loss 
  • Joint pain 
  • Mood swings and depression 

How Long Does Hormone Therapy Take?

How long hormone therapy, or breast cancer estrogen blocker medication, is given depends on several factors such as which hormones the patient has tested positive for, previous treatments, whether they are pre-menopausal or post-menopausal, and more. Taking a combination of the drugs can be more effective than just taking one. Talk with your oncologist about which drug you could benefit from.  

For pre-menopausal women, this schedule often followed is: 

  • AI plus a type of ovarian suppression for 5 to 10 years 
  • Tamoxifen, with or without ovarian suppression for 5 to 10 years 
  • Tamoxifen, with or without ovarian suppression for 5 years, then an AI for 5 years if menopause occurs throughout treatment 

For women that are post-menopausal during treatment, below are some examples of a typical schedule: 

  • AI for 5 to 10 years 
  • AI for 2 to 3 years, followed by tamoxifen for 2 to 3 years 
  • Tamoxifen for 2 to 3 years, then an AI for 2 to 3 years  
  • Tamoxifen for 2 to 3 years, then an AI for 5 years 
  • Tamoxifen for 4½ to 6 years, then an AI for 5 years 
  • Tamoxifen for 5 to 10 years 
  • For patients who are not eligible to for an AI, tamoxifen for 5 to 10 years can sometimes be an option 

The higher the risk of the cancer returning post-treatment, the more likely that the patient will take hormone therapy drugs for longer than five years. 

Clinical Trials for Breast Cancer

Clinical trials give early access to cancer patients seeking the latest therapies from cancer research. For some patients, clinical trials are their best option for treatment. Before being approved by the FDA, clinical trials need to go through several phases of treating patients to ensure the drug’s efficacy and safety. To create a safe environment to evaluate the drug, there is specific inclusion and exclusion criteria for each clinical trial. You can find breast cancer clinical trials you may be eligible for to access breast cancer treatment options using our free AI-powered platform. 


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