Inclusion problems

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.

Inclusion Criteria:

• Postmenopausal status
• Currently being treated with an AI in the adjuvant setting (minimum for 8 weeks)
• AIMSS as determined by new or worsened musculoskeletal complaints following AI therapy
• Vitamin D deficiency (<30ng/ml)
• Caucasian

Exclusion Criteria:

• Hormone replacement therapy last 6 months
• Current use or in the last 12 months of bisphosphonates
• Tamoxifen use in last 6 months
• History of kidney stones
• History of hypercalcemia/hypercalciuria or hyperthyroidism
• Paget's disease of the bone
• Current use of Digitalis/digoxin or thiazide diuretics
• Current use of vitamin D (or multivitamin) supplementation should be stopped