Placebo-controlled Trial With Vitamin D to Prevent Worsening/Relieve Aromatase Inhibitor-induced Musculoskeletal Symptoms in Breast Cancer Patients

The third generation oral aromatase inhibitors (AIs) are increasingly being used in the management of estrogen receptor positive breast cancer. One of the issues related with administration of oral AIs is their side effects, particularly on the musculoskeletal system. Although the prevalence and importance of arthralgia and myalgia occurring in BC patients receiving adjuvant AIs are evident, the mechanisms clearly explaining these invalidating symptoms are unknown. In this project, we aim to unravel the interaction between vitamin D and musculoskeletal adverse events experienced by AI users. We will also evaluate how vitamin D supplementation affects AI-induced musculoskeletal symptoms in breast cancer patients, by means of a randomized placebo-controlled double blind clinical trial. We will assess changes in the musculoskeletal system by using magnetic resonance imaging of joints, hand grip strength and also monitor serum IGF-I and estrogen levels together with bone resorption and formation markers.