Aromatase inhibitor-induced arthralgia substantially improved in women who received omega-3 fatty acid capsules, as well as in those who took placebo, according to a study published online May 4 in the Journal of Clinical Oncology.

Brief Pain Inventory (BPI) worst pain scores were significantly lower than were baseline scores after treatment with O3-FAs and placebo. On the 10-point scale, the median scores reported by women taking O3-FAs were lower by 1.69, 1.74, and 2.23 at 6, 12, and 24 weeks, respectively (P < .001). For those taking placebo, the scores also were significantly lower: 1.36, 1.50, and 1.81 points at 6, 12, and 24 weeks respectively (P < .001). Differences between the groups were not significant, reported Dr. Dawn Hershman of the Herbert Irving Comprehensive Cancer Center, Columbia University, New York, and associates (J. Clin. Onc. 2015 May 4 [doi: 10.1200/JCO.2014.59.5595]).

“The improvement in symptoms in both the treatment and placebo groups was unexpected. The magnitude of the expected placebo effect reported in the literature can vary from 6% to 59% and can be higher in symptom-management studies. We found an effect >50%,” Dr. Hershman and associates wrote.

The large placebo effect may have resulted from a number of factors, including the natural history of arthralgia (which can improve over time), the soy/corn oil ingredients in the placebo capsule, or O3-FA contamination in the placebo arm due to supplementation by patients.

There are no proven therapies for AI-associated arthralgia, and its mechanism is unclear. Evidence suggests that inflammation may play a role. Given that studies have shown O3-FAs may benefit symptoms of rheumatoid arthritis, this multicenter, placebo controlled trial evaluated whether O3-FAs reduce pain and stiffness in 249 women undergoing adjuvant AI therapy for early-stage breast cancer.

At week 12, patients who received O3-FAs had significantly decreased serum triglyceride levels (–22.1 mg/dL, P < .001) and increased HDL (2.9 mg/dL, P < .007). Triglyceride and HDL levels for the placebo arm did not significantly change, which suggests that O3-FA contamination in the placebo arm was not a factor in the high placebo effect. Other serum measures (cholesterol, CRP, and LDL) did not significantly change for either group, Dr. Hershman and associates said.