Effect of vitamin D supplementation on aromatase inhibitor-related musculoskeletal side effects for breast cancer: B-ABLE cohort

Objective: To assess the effect of vitamin D supplementation on musculoskeletal complications related to aromatase inhibitor (AI) treatment in patients with breast cancer. Material and methods: Prospective observational study of women undergoing AI treatment, recruited in the B‐ABLE cohort. Patients with baseline serum 25 (OH) D (25‐hydroxyvitamin D) levels 0 at 3 months, was evaluated using logistic regression. Results: Vitamin D supplementation at the start of AI treatment decreased the risk of both incident arthralgia and its worsening. The effective threshold of 25 (OH) D in serum to reduce joint pain was established at 40 ng/ml. However, this threshold was not significantly related to bone changes at one year of follow‐up. However, vitamin D levels were in‐ versely correlated with lumbar spine bone loss (LS) (β=0.177% [95% CI: 0.014 to 0.340]). Conclusions: Vitamin D supplementation aimed at achieving serum 25(OH)D levels of at least 40 ng/ml is protective for arthralgia. Vitamin D levels at three months could predict the risk of bone loss in LS at one year of AI treatment. The‐ refore, high doses of vitamin D are recommended in these patients, who are more prone to musculoskeletal conditions.