Association between body mass index and response to duloxetine for aromatase inhibitor-associated musculoskeletal symptoms in SWOG S1202.

BACKGROUND: Aromatase inhibitor (AI)-associated musculoskeletal symptoms (AIMSS) negatively impact adherence to and persistence with therapy. In SWOG S1202, patients with AIMSS who were treated with duloxetine, a serotonin norepinephrine reuptake inhibitor, reported improvement in pain by 12 weeks compared with placebo. Based on the authors' prior observation that responses to pain interventions differ between obese and nonobese patients, the current study examined whether response to duloxetine therapy differed by obesity status.

METHODS: In SWOG S1202, a total of 299 AI-treated postmenopausal women with stage I to III (AJCC 7th Edition) breast cancer who developed new or worsening average pain were enrolled, randomized to duloxetine or placebo, and treated for 12 weeks. Patient-reported outcomes were obtained at baseline and through 12 weeks. Patients were categorized into nonobese (body mass index [BMI] <30 kg/m2 ) or obese (BMI ≥30 kg/m2 ). The authors tested the interaction between intervention and obesity with respect to average pain at 12 weeks in the 289 eligible patients, using a P value of .05 to indicate statistical significance.

RESULTS: In approximately 54% of evaluable patients with a BMI ≥30 kg/m2 , the reduction in the mean average pain score between baseline and 12 weeks was statistically significantly greater for patients treated with duloxetine compared with those receiving placebo (-2.73 vs -1.64 points; P = .003). Conversely, in the nonobese patients, the reduction in the mean average pain score was similar in the 2 cohorts (-2.46 vs -2.34 points; P = .75). The P value for interaction was .02, thereby meeting the threshold criteria of the current study. Similar findings were evident for other pain-related patient-reported outcomes.

CONCLUSIONS: In this trial, obese patients with AIMSS obtained more analgesic benefit from duloxetine compared with nonobese patients. Additional studies are warranted to determine the biologic basis for these findings.