The Effect of Vitamin D Status on Bone Mineral Density (BMD) and Aromatase-Induced Musculoskeletal Syndrome (AIMSS) in Post- menopausal Women Receiving An AI for Early Breast cancer

Background: An AI use is associated with bone health and musculoskeletal adverse events. Appropriate vitamin D supplementation would mitigate such side effects. Patients and Methods: Post-menopausal breast cancer patients taking adjuvant letrozole were recruited. Baseline plasma 25(OH)D, BMD and HAQ-DI questionnaire were obtained to determine the aromatase-induced bone loss (AIBL) and musculoskeletal syndrome (AIMSS). The prevalences of vitamin D insufficiency/deficiency, AIBL and AIMSS and the effect of vitamin D repletion on AIMSS were investigated. Results: Eighty-eight patients were participated. Forty-two (42%) percent and 18.2% of women had vitamin D insufficiency and deficiency, respectively. High BMI ( > 25 kg/m ² ) (OR 3.66, 95% C.I., 1.31-10.22; p = 0.013) and formulations/dosages of vitamin D supplementation with lower equivalent dose than calciferol of 20,000 IU/week (OR 3.84, 95%C.I., 1.34-10.97; p = 0.012) were independently correlated with low plasma 25(OH)D level (≤30 ng/ml). Ageing ( > 65 years) (OR 6.77, 95% C.I., 1.36-33.63 p= 0.019), low BMD (OR 5.59, 95% C.I., 1.07-29.23; p = 0.041) and low plasma 25(OH)D level (OR 8.98, 95% C.I., 1.52 - 53.19 ; p = 0.016) were the significant predictors of developing osteoporosis. Nineteen of the participants (21.6%) had AIMSS and 68.4% of them also had low baseline 25(OH)D level. Upon restoration of vitamin D level, the musculoskeletal pain was statistically improved. Conclusions: The prevalences of both vitamin D insufficiency/deficiency and osteoporosis were comparable to the Western countries. To examine plasma 25(OH)D and BMD prior to and during adjuvant AI in accordance with appropriate vitamin D repletion are strongly recommended.