This analysis was performed to further characterise treatment-emergent hypocalcaemia in patients with bone metastases receiving denosumab. Laboratory abnormalities and adverse events of hypocalcaemia in patients with metastatic bone disease were analysed using data from three identically designed phase 3 trials of subcutaneous denosumab 120 mg (n = 2841) versus intravenous zoledronic acid 4 mg (n = 2836). The overall incidence of laboratory events of hypocalcaemia grade ⩾ 2 was higher with denosumab (12.4%) than with zoledronic acid (5.3%). Hypocalcaemia events were primarily grade 2 in severity and usually occurred within the first 6 months of treatment. Patients who reported taking calcium and/or vitamin D supplements had a lower incidence of hypocalcaemia. Prostate cancer or small-cell lung cancer, reduced creatinine clearance and higher baseline bone turnover markers of urinary N-telopeptide of type I collagen (uNTx; > 50 versus ⩽ 50 nmol/mmol) and bone-specific alkaline phosphatase (BSAP; > 20.77 μg/L [median] versus ⩽ 20.77 μg/L) values were important risk factors for developing hypocalcaemia. The risk associated with increased baseline BSAP levels was greater among patients who had > 2 bone metastases at baseline versus those with ⩽ 2 bone metastases at baseline. Hypocalcaemia was more frequent with denosumab versus zoledronic acid, consistent with denosumab's greater antiresorptive effect. Low serum calcium levels and potential vitamin D deficiency should be corrected before initiating treatment with a potent osteoclast inhibitor, and corrected serum calcium levels should be monitored during treatment. Adequate calcium and vitamin D intake appears to substantially reduce the risk of hypocalcaemia.

Bone metastases place patients at increased risk of skeletal-related events (SREs), including pathologic fractures, spinal cord compression, severe pain requiring radiotherapy or surgery, and hypercalcemia, because of increased osteoclast-mediated bone resorption. Denosumab, a fully human monoclonal antibody, decreases bone resorption by inhibiting RANKL, which mediates osteoclast activity. We compared the effects of denosumab in two phase 2 studies in patients with bone metastases naive to intravenous bisphosphonate therapy (IV BP; n = 255) and those with elevated levels of the bone resorption marker urinary N-telopeptide (uNTX) despite ongoing IV BP treatment (n = 111). Patients were randomized to receive IV BP every 4 weeks or subcutaneous denosumab every 4 weeks (30/120/180 mg) or every 12 weeks (60/180 mg). Patients treated with denosumab experienced a rapid and sustained reduction in bone turnover regardless of prior IV BP exposure. After 25 weeks, the median uNTX reduction was 75% (IV BP-naive) and 80% (prior IV BP) after denosumab treatment and 71% (IV BP-naive) and 56% (prior IV BP) in the IV BP arms. Denosumab patients with prior IV BP exposure had marked suppression of the osteoclast marker TRAP-5b (median reduction: denosumab 73%, IV BP 11%). SRE incidence was low across both studies. In patients previously treated with BPs, the rate of first on-study SRE was lower in the denosumab groups (8%) than the IV BP group (17%). Denosumab appeared to be well tolerated in both studies. Denosumab suppresses bone resorption markers independently of prior BP treatment, even in patients who appear to respond poorly to BPs. © 2010 American Society for Bone and Mineral Research.

Background: The proto-oncogene Src is an important non-receptor protein tyrosine kinase involved in signaling pathways that control cell adhesion, growth, migration and differentiation. It negatively regulates osteoblast activity, and, as such, its inhibition is a potential means to prevent bone loss. Dasatinib is a new dual Src/Bcr-Abl tyrosine kinase inhibitor initially developed for the treatment of chronic myeloid leukemia. It has also shown promising results in preclinical studies in various solid tumors. However, its effects on the differentiation of human osteoblasts have never been examined. Methods: We evaluated the effects of dasatinib on bone marrow-derived mesenchymal stromal cells (MSC) differentiation into osteoblasts, in the presence or absence of a mixture of dexamethasone, ascorbic acid and β-glycerophosphate (DAG) for up to 21 days. The differentiation kinetics was assessed by evaluating mineralization of the extracellular matrix, alkaline phosphatase (ALP) activity, and expression of osteoblastic markers (receptor activator of nuclear factor kappa B ligand [RANKL], bone sialoprotein [BSP], osteopontin [OPN]). Results: Dasatinib significantly increased the activity of ALP and the level of calcium deposition in MSC cultured with DAG after, respectively, 7 and 14 days; it upregulated the expression of BSP and OPN genes independently of DAG; and it markedly downregulated the expression of RANKL gene and protein (decrease in RANKL/OPG ratio), the key factor that stimulates osteoclast differentiation and activity. Conclusions: Our results suggest a dual role for dasatinib in both (i) stimulating osteoblast differentiation leading to a direct increase in bone formation, and (ii) downregulating RANKL synthesis by osteoblasts leading to an indirect inhibition of osteoclastogenesis. Thus, dasatinib is a potentially interesting candidate drug for the treatment of osteolysis through its dual effect on bone metabolism.

A systematic literature review was conducted to quantify populations of patients with primary breast cancer in whom bone metastases were detected at study start or during follow-up. Searches were performed in PubMed and EMBASE using terms related to breast cancer and bone metastases. Articles had to have been published 01/01/99-31/12/13, and to report data on the proportion of patients with bone metastases among patients with breast cancer. In total, 156 articles were included in the meta-analysis. A median of 12% of patients with stage I-III breast cancer developed bone metastases during a median follow-up of 60 months. Of patients who developed metastatic disease during follow-up, 55% (median) had bone metastases. Of those with metastatic breast cancer at study start, 58% (median) had bone metastases. These data help to inform on the global burden of bone metastases by defining patient populations that are at risk of developing bone metastases.

Women with breast cancer, particularly individuals diagnosed at a relatively early age, have an increased incidence of fractures. Fractures can have serious clinical consequences including the need for major surgery, increased morbidity and mortality, increased cost of disease management, and reduced quality of life for patients. The primary cause of the increased fracture risk appears to be an accelerated decrease in bone mineral density (BMD) resulting from the loss of estrogenic signaling that occurs with most treatments for breast cancer, including aromatase inhibitors. However, factors other than BMD levels alone may influence treatment decisions to reduce fracture risk in this setting. Our purpose is to review current evidence for BMD loss and fracture risk during treatment for breast cancer and discuss pharmacologic means to reduce this risk.