A new report describing the results of a trial of high dose vitamin D supplementation in women taking the aromatase inhibitor Arimidex has reported that such supplementation reduces musculoskeletal symptoms and may prevent bone loss.

The study included 60 patients with early breast cancer and aromatase inhibitor-induced musculoskeletal symptoms who were grouped according to their baseline circulating vitamin D (25OHD) levels. All study participants received 400 units of vitamin D and 1,000 milligrams of calcium daily throughout the study. The authors used vitamin D2 rather than vitamin D3 in the study because it metabolizes more quickly and is less likely to cause symptoms of overdose. Women in stratum A, who had levels of vitamin D most observers would consider low (20-29 ng/ml 25OHD), received either high dose vitamin D capsules (50,000 IU) weekly for eight weeks, then monthly for four months, or placebo. Women in stratum B, who had clearly deficient baseline levels of vitamin D (10-19 ng/ml), received either high dose vitamin D for 16 weeks, then monthly for two months, or placebo. The high dose vitamin D was given in addition to the 400 units of vitamin D per day that all study participants received. Musculoskeletal symptoms due to Arimidex were assessed using the Brief Pain Inventory-Short Form (BPI-SF), the Fibromyalgia Impact Questionnaire (FIQ), and the Health Assessment Questionnaire-Disability Index (HAQ-DI) at baseline and at the two, four and six month marks. Bone mineral density was measured at baseline and at six months. Study participants in the two groups had comparable baseline characteristics.

At two months, each of the pain and disability scores were better in the high dose vitamin D groups than in the placebo groups. The beneficial effect on musculoskeletal symptoms of high dose vitamin D was found to be stronger across all time points in Stratum B (the vitamin D deficient group) than Stratum A (the low vitamin D group). Bone mineral density at the femoral neck (the top of the thighbone) declined in the placebo groups and did not change in the high dose vitamin D groups. The authors conclude that weekly high dose vitamin D improves aromatase inhibitor-induced musculoskeletal symptoms and may have a positive effect on bone health. Vitamin D supplementation strategies for breast cancer patients on aromatase inhibitors should be further investigated.

Comments regarding the study

Caution is advised in taking large doses of vitamin D during aromatase inhibitor treatment since vitamin D might reduce the treatment's effectiveness. More research is needed to determine whether vitamin D is beneficial or detrimental to the prognosis of breast cancer survivors taking aromatase inhibitors.