About 50% of breast cancer patients taking aromatase inhibitors report musculoskeletal pain or worsening of symptoms, and 18% to 30% report fatigue. These are important reasons for women to improve their chances of terminating treatment. The results of the VITAL study, a phase III randomized, placebo-controlled, double-blind trial enrolling 147 women with breast cancer, were presented at the 2012 ASCO Annual Meeting and found that the addition of vitamin D3 (30,000 IU/week) to letrozole treatment reduced skeletal muscle sarcopenia. The study included 147 patients with stage I-III breast cancer, all receiving letrozole treatment + vitamin D (600 IU/d) + calcium (1200 mg/d). were randomly assigned to receive an additional 30,000 IU/week of vitamin D3 or placebo, with vitamin D levels tested at baseline levels, 12 weeks and 24 weeks, and symptom investigation. Three patients in the placebo group, discontinued treatment early due to skeletal muscle sarcoidosis. In the vitamin D group, vitamin D levels were 22, 53, and 57 ng/mL at baseline, 12 weeks, and 24 weeks, respectively, and 25, 32, and 31 ng/mL in the placebo group, respectively.