The painful side effects of some breast cancer drugs lead many women to stop taking them, but results from a new study from Columbia University Irving Medical Center (CUIMC) may help some women find relief and continue their treatment.

The findings suggest that in some women, omega-3 supplements can significantly reduce severe joint pain caused by a commonly used class of breast cancer drugs. The results were presented at the American Society of Clinical Oncology annual meeting in Chicago.

Drugs called aromatase inhibitors are commonly used to treat postmenopausal women with hormone receptor-positive breast cancer. These drugs, which are typically prescribed for 5 to 10 years, increase survival and reduce the chance of a cancer recurrence.

However, 45% to 60% of women taking aromatase inhibitors experience moderate to severe joint pain (arthralgia). Within 2 years, approximately 25% of women with arthralgia stop taking aromatase inhibitors due to this debilitating side effect. Another 25% cope by taking the medications intermittently, dampening their therapeutic effect. Arthralgia caused by aromatase inhibitors is more common in obese women, as excess weight can increase stress on the joints.

“We know that patients who have side effects from aromatase inhibitors are more likely to discontinue their treatment, which can raise their risk of a breast cancer recurrence,” says Dawn Hershman, MD, a breast cancer specialist at NewYork-Presbyterian/CUIMC and senior author of the study.

“When we think of ways to control treatment side effects and improve adherence, it’s important to offer interventions that are acceptable to patients and are unlikely to introduce new side effects that could interfere with treatment.”

Studies have shown that taking omega-3 supplements can lead to decreased joint pain in patients with rheumatoid arthritis, an inflammatory disease. However, in breast cancer patients with aromatase inhibitor-related joint pain, previous data on omega-3 supplements have been mixed.

In an earlier multicenter clinical trial led by Hershman, about half of 249 breast cancer patients with moderate to severe joint pain were randomized to take omega-3 supplements for 6 months; the other half took a placebo. Although both groups reported a clinically meaningful decrease in joint pain, the placebo and omega-3s reduced pain by roughly the same amount.

“Since women with obesity tend to have more joint symptoms with aromatase inhibitors, we wanted to find out if this group of patients could also benefit more from omega-3 supplements,” says Sherry Shen, MD, an internal medicine resident at NewYork-Presbyterian/CUIMC and the study’s lead author. “So we decided to reanalyze the data from the previous study to see if the effect of omega-3 fatty acids varied with body mass index.”

In the reanalysis, the researchers found that in obese women, omega-3 use was associated with an average decrease in pain of nearly three points (on a 1-to-10 pain scale), which was statistically different from the 1.5-point decrease associated with the placebo. No difference in pain relief was found between omega-3s and placebo among women with a BMI of less than 30.

The authors note that while these findings are preliminary and need to be confirmed with additional studies, they suggest that taking omega-3s could lead to improved adherence to aromatase inhibitor treatment in obese patients.