Prevalence and clinical outcomes of vitamin D deficiency among Japanese multiple myeloma patients: a single-center observational study

Purpose: Vitamin D is a fundamental mediator of skeletal metabolism, but also plays an important role in the pathophysiology of multiple myeloma (MM). Recent studies have shown an association between vitamin D deficiency and racial outcomes in MM patients. The aim of this study was to clarify the prevalence of vitamin D deficiency among Japanese MM patients and the association between vitamin D status and clinical outcomes Methods: We tested serum 25-hydroxyvitamin D (25(OH)D) levels in 68 MM patients at a single Japanese institution from December 2015 to March 2016. Results: Median serum 25(OH)D level was 22 ng/mL, with 32% and 51% of patients showing vitamin D deficiency (<20 ng/mL) and insufficiency (20–29 ng/mL), respectively. The 25(OH)D levels were not associated with sex, age, duration of MM disease, stage, or skeletal morbidity. In 15 patients with suboptimal 25(OH)D levels, supplementation with cholecalciferol (1000 IU/day) significantly increased 25(OH)D levels and decreased parathyroid hormone levels in all patients. Serum total procollagen type 1 N-propeptide levels, but not serum tartrate-resistant acid phosphatase 5b, were increased in patients who achieved complete remission. Overall survivals from vitamin D measurement and from MM diagnosis were significantly worse in the vitamin D-deficient group than in the vitamin D-deficient/sufficient group. Conclusion: Most Japanese MM patients had less-than-sufficient levels of serum vitamin D, with one-third being deficient. Vitamin D deficiency also predicted poor overall survival in Japanese MM patients. Further studies are needed to investigate whether vitamin D supplementation can overcome the poor survival of MM patients.