The safety and efficacy of denosumab were retrospectively assessed in patients with multiple myeloma. This study included 25 patients treated with denosumab from May 2012 to March 2014. No skeletal-related events (SREs) due to multiple myeloma occurred. Urine N-telopeptide/creatinine decreased in all of 5 assessed patients 1 month after denosumab treatment, and urine deoxypyridinoline/creatinine decreased in 4 of 5 assessed patients. Osteonecrosis of the jaw was not observed. Hypocalcemia developed in 11 patients (44%). One patient with Grade 4 hypocalcemia complained of numbness of the extremities; however, the other patients had no complaint. On univariate analysis, the incidence of hypocalcemia was significantly higher in patients with than in those without renal insufficiency (p = 0.007) and patients with high than in those with low β-2-microglobulin (p = 0.017). On multivariate analysis, renal insufficiency was a risk factor for the development of hypocalcemia (p = 0.01). The patients who had prophylactic Ca and vitamin D3 supplementation had a significantly lower incidence of hypocalcemia than the others (p = 0.047). In conclusion, treatment with denosumab is safe and effective to prevent SREs in patients with multiple myeloma. Prophylaxis for hypocalcemia with calcium and/or vitamin D3 supplementation is necessary, especially in patients with renal insufficiency.
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