Risk factors for joint symptoms in postmenopausal Japanese breast cancer patients treated with anastrozole: a prospective multicenter cohort study of patient-reported outcomes

Background Endocrine treatment-related adverse events have a strong impact on patients’ quality of life and sometimes result in treatment discontinuation. Since joint symptoms are the most frequently recognized side effect of aromatase inhibitors, evaluation of associated risk factors may yield significant findings. Patients and methods A total of 391 postmenopausal Japanese women with estrogen receptor-positive breast cancer and treated with adjuvant anastrozole were enrolled from 28 centers for assessment of patient-reported outcomes (PROs) in this prospective cohort study (SAVS-JP, UMIN000002455). Patients completed the self-report questionnaire at baseline and after 3, 6, 9, and 12 months of treatment for evaluation of frequency of treatment-related joint symptoms (arthralgia, decrease in range of joint motion, and joint stiffness). Results We obtained PROs from 362 patients (92.6 %) at baseline and at one or more subsequent points. New or worsening from baseline of joint symptoms were reported by 260 patients (71.8 %). More than 90 % of the symptoms were mild or moderate and nearly 80 % had occurred by 6 months. Multivariate analysis showed that a short time span after menopause [odds ratio (OR) 0.95, 95 % confidence interval (CI) 0.90–0.99; P = 0.02] and adjuvant chemotherapy (OR 2.29, 95 % CI 1.06–4.95; P = 0.03) were significant independent risk factors for joint symptoms. No significant relationships between body mass index (BMI) and joint symptoms were identified. Eighteen patients discontinued treatment during the 1st year and eight of them reported joint symptoms. Conclusion Taking into consideration that PROs may yield higher prevalence rates than physician ratings for symptoms published in pivotal clinical trials, we found that a short time span after menopause and use of adjuvant chemotherapy, but not high BMI, were significantly associated with joint symptoms. These findings might prove useful for counseling before initiating treatment with adjuvant aromatase inhibitors in postmenopausal Japanese women.