Randomized, Double-Blind, Placebo-Controlled Phase II Clinical Trial on the Use of Uncaria tomentosa (Cat's Claw) for Aromatase Inhibitor-Induced Arthralgia: A Pilot Study

Introduction: Aromatase inhibitors (AI) are widely used in adjuvant breast cancer treatment, and diffuse articular pain secondary to AI use is the most common cause of treatment discontinuation. Uncaria tomentosa (cat’s claw) has antiinflammatory activity and is used to treat arthrosis and arthritis. Patients and Methods: This prospective, single-center, double-blind, randomized, placebo-controlled phase II study analyzed 70 patients with breast cancer undergoing AI therapy with complaints of arthralgia. The patients received 100 mg of the dry extract of Uncaria tomentosa three times daily for 4 weeks. At the beginning and end of the study, patients answered the Brief Pain Inventory (BPI), Disability Arm, Shoulder, and Hand (DASH), Lequesne, SF-36 Quality of Life questionnaires, completed a visual analog scale (VAS) for pain, and underwent laboratory testing. Results: U. tomentosa was not more effective than the placebo. No evidence of grade 3 or 4 toxicity was found. In addition, no significant differences were seen in laboratory results or inflammatory markers between the two study groups. Conclusion: Dry extract of U. tomentosa was safe but ineffective in reducing AI-induced arthralgia compared with the placebo. Furthermore, the plant extract had no detectable anti-inflammatory activity.