Breast Cancer Pain Management Month: Estrogen Blocking Therapy Associated With Musculoskeletal Pain

Statue of woman contemplating

By Dr. Peter Abaci

Breast cancer is the leading cause of cancer among women, with the majority of cases involving post-menopausal women. About 1 out 8 women will develop invasive breast cancer during their lifetime, and it is estimated that about 230,000 women will be diagnosed with invasive breast cancer this year along with 62,000 non-invasive cases. For many, they will develop hormone receptor positive forms of breast cancer which means that estrogen and estrogen-like compounds stimulate the cancer cells to grow. As a result, treatments that block estrogen from binding to cancer cells have become important in improving outcomes for breast cancer treatment of hormone receptor positive cancer cells.

One class of drugs that have proven to be effective for post-menopausal women is the aromatase inhibitors (AIs). Common brand names include Arimidex, Femara, and Aromasin. While AIs have been successful in helping to improve survival rates, their long-term use can be associated with side effects. Up to a third of women on AIs can develop musculoskeletal symptoms and more than half have been shown to develop joint pain. The most common symptoms include morning pain and stiffness of the hands, fingers, knees, hips, shoulders, and back. In fact, treatment with AIs seem to result in a significant rise in the incidence of carpal tunnel syndrome, including a seven-fold higher rate of carpal tunnel surgery compared with patients not treated with AIs. 

Reduced levels of estrogen have been shown to be associated with an increased sensitivity to pain in the body as well as a degradation of cartilage. In particular, some studies have suggested that the tendons around the joints are particularly affected by treatment with AIs. MRI studies have shown signs of inflammation around the tendons, including fluid buildup. In some cases, the tendon irritation can cause severe discomfort. One of the more common syndromes associated with AI use is tenosynovitis causing pain in the wrist near the thumb.  Another side effect of AI use that can lead to pain management issues is osteoporosis, as its estrogen blocking properties inhibits bone density.

Unfortunately, painful side effects of AIs can lead to a decrease in physical activity and a lower level of function with daily activities. This has necessitated a need for pain treatments to offset painful musculoskeletal symptoms. It is important that your doctors investigate carefully the potential causes to provide the best treatments. First line treatments may include the use of non-steroidal anti-inflammatory medications and ice or heat. In some cases supplementation with vitamin D and calcium is appropriate. For painful joints, cortisone injections around inflamed tendons may help. Other therapies that have been looked at include acupuncture, nerve pain medications like duloxetine and gabapentin, and therapeutic exercises. 

If you are having pain and joint aches while on an AI while undergoing breast cancer treatment, make sure you talk to your doctor about finding the best strategies for help.

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