Defining the aromatase inhibitor musculoskeletal syndrome: a prospective study.

OBJECTIVE: To define the musculoskeletal syndrome associated with use of aromatase inhibitors (AIs), specifically, to describe its incidence, time to onset, risk factors, and clinical presentation. METHODS: Postmenopausal women with hormone-sensitive, nonmetastatic breast cancer starting AI therapy were enrolled in this prospective cohort study. They underwent complete rheumatologic evaluation and contrast-enhanced magnetic resonance imaging (MRI) of the hands and wrists prior to starting AI, at 3 and 6 months. The primary outcome was change in grip strength. RESULTS: Twenty-eight (54%) of 52 women reported new or worsening musculoskeletal symptoms. Two discontinued AIs due to pain. Mean time to symptom onset was 6 weeks (range 2-18 weeks), and 75% of symptomatic patients developed symptoms by 8 weeks. Later-stage cancer and worse quality of life (QOL) pretreatment were significantly associated with symptom development. Sixty-eight percent of symptomatic subjects had involvement of the hands; however, there was no difference in the mean change in grip strength (-2.9 kg versus -1.3 kg; P = 0.6). Among symptomatic subjects, 46% had evidence of focal tenosynovitis of the hands and feet on examination. Although some symptomatic subjects had new MRI abnormalities, Rheumatoid Arthritis Magnetic Resonance Imaging Scoring did not significantly change. CONCLUSION: The incidence of AI-associated musculoskeletal syndrome is more than 50%, with most women developing symptoms by 8 weeks. The key finding in symptomatic women was focal tenosynovitis of the hands and feet, without evidence of autoimmune disease or systemic inflammation. Later-stage cancer and poorer QOL were predictive of symptom development.