Joint Pain: A Common Side Effect of Certain Breast Cancer Treatments

Arthritis-like symptoms are associated with aromatase inhibitors
woman sitting on edge of bead holding painful knee

When you think of achy joints, do you think of arthritis? While arthritis is a common cause, joint pain can also be the result of something you might not expect.

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For example, joint pain can occur as a result of cancer treatment. This is a particular concern for postmenopausal women with breast cancer who take hormone therapy drugs called aromatase inhibitors.

Aromatase inhibitors, which include letrozole (Femara®), anastrozole (Arimidex®) and exemestane (Aromasin®), are a standard treatment for what is called hormone-receptor positive breast cancer.

“These drugs are quite good at preventing cancer recurrences,” says oncologist Susan LeGrand, MD.

But joint pain, a frequent side effect, can limit their usefulness, because some women are so bothered by it that they stop taking the medication. “The goal is to make it manageable,” Dr. LeGrand says.

Who takes aromatase inhibitors?

Most, but not all, breast cancer tumors are hormone-receptor positive. This means that the cancer cells have receptors that recognize the hormones estrogen or progesterone. These hormones can attach to the receptors, which allow them to enter the cell. Once inside the cell, estrogen and progesterone can fuel cancer growth.

Ridding the body of all estrogen can help deny the cancer this source of fuel. After menopause, a woman’s ovaries no longer produce estrogen. But an enzyme called aromatase converts hormones produced in the adrenal gland into estrogen. Aromatase inhibitors block the action of aromatase, which leads to less estrogen in the body.

Aromatase inhibitors are used mainly in two situations. First, a woman newly diagnosed with a breast cancer tumor of a specific size who has undergone surgery will be given an aromatase inhibitor to take for five years, and possibly up to 10 years, to prevent the cancer from coming back.

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“This is someone who doesn’t have cancer right now,” Dr. LeGrand says. “It’s given for prevention.”

Second, a woman who has hormone-positive breast cancer that has spread (metastasized) can be given an aromatase inhibitor as the first therapy.  

The downside: joint pain

While aromatase inhibitors are very effective, they have potential side effects. Studies have found that anywhere from 25% to 50% of women who take the drugs experience joint pain or muscle pain.

Joint symptoms can affect the fingers, wrists, elbows, shoulders, knees and ankles. “It’s problematic because, if you are using it for prevention, you don’t want to mess up their quality of life,” Dr. LeGrand explains.

Some women stop taking the drug before the five years are up because of joint discomfort.

Dealing with joint pain from breast cancer treatment

It’s not known exactly why aromatase inhibitors cause joint pain. And so far, there is no way to predict who will experience it.

If you’re taking these drugs and feel achy joints or other symptoms, it’s important to talk to your oncologist. 

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Joint pain is mostly treated with acetaminophen (Tylenol®) or nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin®, Advil®) or naproxen (Aleve®). If the pain is severe, Dr. LeGrand says she’ll try switching to a different aromatase inhibitor, which might be better tolerated. “That frequently works,” she says.

Some small studies have shown a possible benefit with nondrug options, including exercise, acupuncture and omega-3 fatty acid supplements. These continue to be studied.

“Exercise has the added benefit of helping with fatigue, which can also be a problem for people on the drugs,” she says.

Arthritis is an irreversible condition, but joint pain from aromatase inhibitors will subside once the medication is stopped. Just don’t stop too soon. To get the full benefit of an aromatase inhibitor, you need to take it consistently for as long as your doctor has prescribed it.

This article originally appeared in Cleveland Clinic Arthritis Advisor.

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