What Are the Side Effects of AROMATASE INHIBITORS Used in Breast Cancer?

Some breast cancer cells carry sites on their surfaces to which the hormones estrogen or progesterone bind, namely  receptors. These receptors are detected by applying various special stains to a biopsy sample taken from the tumor tissue. Breast tumors that stain positive for estrogen or progesterone receptors are called hormone receptor-positive breast cancer. In these patients, the hormone estrogen causes cancer cells to grow and multiply.

Below, you can see our infographic poster explaining the types of breast cancer and hormone-positive breast cancer:

What Is an Aromatase Inhibitor?

Aromatase inhibitors are hormone therapy drugs used to treat hormone receptor-positive breast cancer. There are 3 different aromatase inhibitors (the active ingredient is given first, followed by the brand name in parentheses):

• Anastrozol (Arimidex, Aristu)
• Eksemestan (Aromasin)
• Letrozol (Femara, Letu)

 They are used to treat breast cancer in the following circumstances:

• In postmenopausal women.
• Also in women who have ovarian suppression.

Note: The ovaries (female ovaries) are suppressed in 3 ways: surgical removal, radiotherapy, and medication. 

What Are the Side Effects of Aromatase Inhibitors?

Joint and Muscle Pain

Joint pain (arthralgia) and muscle pain (myalgia) are the most common side effects of aromatase inhibitors. There may be pain in the hands and wrists, feet and ankles, knees, back, or other parts of the body.

Among women taking aromatase inhibitors, nearly half experience joint pain and approximately 15% experience muscle pain. Joint and muscle pain can mimic carpal tunnel syndrome, and in rare cases aromatase inhibitors can cause carpal tunnel syndrome. Although they cause joint and muscle pain, they do not cause joint and muscle damage.

Relieving Joint and Muscle Pain

If you have joint and muscle pain while taking an aromatase inhibitor, talk to your medical oncologist. Your oncologist may recommend anti-inflammatory drugs (such as aspirin or ibuprofen), special exercises, or acupuncture to relieve the pain. They may also switch you to another aromatase inhibitor or recommend tamoksifen.

Bone Health

Compared with tamoksifen, aromatase inhibitors cause a higher rate of loss of bone density, leading to osteoporosis and bone fractures.

Monitoring Bone Health

Your healthcare professional will take a baseline measurement of your bone density. In medical terminology, we call this DEXA (bone mineral densitometry). Future measurements can be compared with this baseline measurement to monitor changes in your bone density.

Bone-Strengthening Treatment

While you are taking an aromatase inhibitor, certain drugs may help prevent osteoporosis. To help maintain your bone density, your healthcare professional may prescribe drugs called bisphosphonates or denosumab.

Health Risks of Bisphosphonates and Denosumab

First, let us recall that high doses of drugs such as bisphosphonates and denosumab, called bone-protective agents in cancer, carry certain bone risks and are generally used in patients with metastatic breast cancer. However, these drugs can cause severe bone, joint, and muscle pain.

If you have any of these symptoms, you should report them to your healthcare professional immediately.

In rare cases, a serious jawbone condition called osteonecrosis may occur. A dental examination is recommended before starting treatment with a bisphosphonate or denosumab. You should also speak with your oncologist before having any dental procedure while taking a bisphosphonate.

• Related topic: Treatment of Hormone-Positive Metastatic Breast Cancer

Exercise, Diet, and Not Smoking

Regular exercise helps protect and strengthen your bones. For example, weight-bearing exercises (exercises that involve standing rather than sitting) help protect bones and reduce the risk of hip fractures. Getting enough calcium and vitamin D (your specialist will tell you whether you are getting enough) and not smoking also help strengthen your bones.

Postmenopausal Symptoms

Hot Flashes and Night Sweats

Hot flashes and night sweats are common in women taking aromatase inhibitors. Although these symptoms become less frequent and less intense over time, they can still be difficult to manage.

If you have hot flashes, talk to your healthcare professional about treating them.

Vaginal Dryness

Vaginal dryness is common in women taking aromatase inhibitors. Unlike hot flashes, vaginal symptoms tend to become worse over time. 

If you have vaginal dryness or other symptoms, you should speak with your healthcare professional about treating these conditions.

Side Effects of Tamoksifen and Aromatase Inhibitors - COMPARISON

Both aromatase inhibitors and tamoksifen can cause menopausal symptoms such as hot flashes, but most of their side effects differ (Table 1).

Your healthcare professional can treat most of these side effects.