Aromatase Inhibitor-Induced Carpal Tunnel Syndrome: Results From the ATAC Trial

Purpose Carpal tunnel syndrome (CTS) is a condition in which the median nerve is compressed, leading to pain and muscle weakness in the fingers and hand. Aromatase inhibitors lead to profound estrogen suppression and may be expected to increase the risk of CTS in postmenopausal women receiving adjuvant therapy for early breast cancer. Patients and Methods The current analyses were based on the 100-month median follow-up data in postmenopausal women in the two monotherapy arms (anastrozole, n = 3,092; tamoxifen, n = 3,094). Here, we investigate the natural history of patients who presented with CTS during adjuvant treatment for breast cancer and the relative importance of a range of known risk factors for CTS. Results After 100 months of follow-up, 80 cases (2.6%) of CTS were reported in the anastrozole arm, compared with 23 cases (0.7%) in the tamoxifen arm (P < .0001). The majority of CTS cases were reported as mild to moderate intensity and occurred early. None of the women stopped treatment medication as a result of CTS. CTS was significantly increased for women who used prior hormone replacement therapy (P = .007) or received prior chemotherapy (P = .01). Those who were 60 years of age or older at entry were at lower risk of CTS compared with their counterparts (P = .002). Conclusion Although the use of anastrozole is associated with a greater incidence of CTS, it is rare, and most cases were of mild to moderate intensity and short duration. CTS has little impact on the overall risk-to-benefit ratio for the use of anastrozole in postmenopausal women with early breast cancer.