Carpal Tunnel Syndrome in Patients Treated With Anastrozole in IBIS-II


Key Points

  • Carpal tunnel syndrome was more common in recipients of anastrozole vs placebo in IBIS-II.
  • Surgical intervention was rare but was more common in those who received anastrozole.

As reported by Spagnolo et al in the Journal of Clinical Oncology, women receiving anastrozole in the International Breast Cancer Intervention Study II (IBIS-II) had a higher incidence of carpal tunnel syndrome compared with those receiving placebo. A higher incidence of carpal tunnel syndrome previously had been reported with aromatase inhibitor vs tamoxifen treatment.

In IBIS-II, postmenopausal women at increased risk of breast cancer were randomized to receive oral anastrozole at 1 mg/d (n = 1,920) or placebo (n = 1,944) for 5 years. As previously reported, anastrozole treatment was associated with a reduced risk of breast cancer.

Increased Risk

In the current exploratory analysis, 65 women in the anastrozole group (3.4%) vs 31 in the placebo group (1.6%) developed carpal tunnel syndrome during a median follow-up of 6.4 years (odds ratio [OR] = 2.16, P < .001). Of 10 patients with severe carpal tunnel syndrome, 8 were in the anastrozole group (P  = .08). Surgical intervention occurred in 18 women in the anastrozole group (0.9%) vs 6 women in the placebo group (0.3%; OR = 3.06, P = .018).

Other factors associated with the increased risk of carpal tunnel syndrome were body mass index of 25 to 30 kg/m2 or > 30 kg/m2 vs < 25 kg/m2 (OR = 1.78, P = .02) and a prior report of musculoskeletal symptoms during the trial (OR = 2.05, P = .001).

The investigators concluded: “The use of anastrozole was associated with a higher incidence of [carpal tunnel syndrome], but few participants required surgery. Further investigations are warranted into the risk factors and treatment of aromatase inhibitor–induced [carpal tunnel syndrome].”

The study was supported by Cancer Research UK, National Health and Medical Research Council Australia, and AstraZeneca.

Ivana Sestak, PhD, of Queen Mary University of London, is the corresponding author of the Journal of Clinical Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.