Severe Hypophosphatemia Following Denosumab Administration in a Hemodialysis Patient with Progressive Prostate Cancer

Severe hypophosphataemia and hypocalcaemia following intravenous ferric derisomaltose and denosumab administration

Serum calcium and phosphorus levels are tightly regulated by the calciotropic hormone parathyroid hormone, fibroblast growth factor 23 and 1,25(OH)2 vitamin D. Commonly prescribed therapies for iron-deficiency anaemia (IDA) such as ferric carboxymaltose and ferric derisomaltose (FDM) have been shown to disrupt phosphorus homeostasis, resulting in hypophosphataemia. Similarly, denosumab use can result in hypocalcaemia due to the inhibition of osteoclastic maturation, activity and survival. Here, we report the development of severe hypophosphataemia and hypocalcaemia in a patient with osteoporosis and IDA following treatment with denosumab and FDM. The patient remained asymptomatic; however, supplementation with calcium, phosphorus and calcitriol replacement was required prior to eventual normalisation of serum levels. Often concomitantly prescribed, little guidance exists regarding electrolyte disturbances following the administration of FDM and denosumab. While hypophosphataemia and hypocalcaemia are relatively uncommon when prescribed individually, synergistic effects likely exist that warrant regular monitoring and occasional supplementation.

Denosumab-associated symptomatic hypophosphatemia in normal kidney function: two case reports

We report two cases of symptomatic severe hypophosphatemia requiring hospitalization and intravenous phosphate supplementation following denosumab therapy for osteoporosis. The two patients had normal kidney function and no previously reported risk factors for hypophosphatemia, both presented neurological symptoms and severe fatigue. After hospital admission, they were treated with intravenous phosphate: serum phosphate improved to normal levels and the patients were discharged with oral phosphate supplements and-in one patient-with oral calcitriol therapy. As prescription rates of denosumab therapy increase, attention should be paid to the risk of developing hypophosphatemia: the risk of such complication may be lower by early and regular monitoring of Ca, Pi, and PTH, as well as early supplementation of phosphate and/or vitamin D as needed. Whenever a patient receiving denosumab therapy complains otherwise unexplained fatigue, exercise intolerance, muscle pain, cramping, and paresthesias, we suggest hypophosphatemia as a potential complication to be ruled out.

Hypophosphatemia in Patients With Multiple Myeloma

Hypophosphatemia is among the most common electrolyte abnormalities, especially among patients with underlying malignancies, and is frequently associated with adverse prognoses. Phosphorus levels are regulated through a number of mechanisms, including parathyroid hormone (PTH), fibroblast growth factor-23 (FGF-23), vitamin D, and other electrolyte levels themselves. Clinically, the findings are nonspecific, and the diagnosis is frequently delayed. This article is a narrative literature review. The PubMed database was searched for relevant articles pertaining to hypophosphatemia causes and consequences in patients suffering from multiple myeloma. We found a variety of causes of hypophosphatemia in patients with multiple myeloma. Tumor-induced osteopenia, although more common among patients with small squamous cell carcinomas, can occur with multiple myeloma as well. Additionally, both light chains themselves and medications can trigger Fanconi syndrome, which leads to phosphorus wasting by the kidney. Bisphosphonates, in addition to being a possible cause of Fanconi syndrome, lead to a decrease in calcium levels, which then stimulates parathyroid hormone (PTH) release, predisposing the patient to significant hypophosphatemia. Additionally, many of the more modern medications used to manage multiple myeloma have been associated with hypophosphatemia. A better understanding of those mechanisms may give clinicians a clearer idea of which patients may need more frequent screening as well as what the potential triggers in the individual patient may be.

Diagnosis and Management of Denosumab-Induced Hypocalcemia and Hypophosphatemia in the Setting of Metastatic Prostate Cancer

Denosumab, a receptor activator of nuclear factor kappa-Β ligand (RANK-L) monoclonal antibody used in osteoporosis and various malignancies, has been shown to cause hypocalcemia shortly after initiation of treatment. There have been few case reports of electrolyte abnormalities in patients managed with long-term treatment with this medication. This report presents the case of a 43-year-old male with metastatic prostate cancer who presented with severe hypophosphatemia and hypocalcemia, initially resistant to repletion. After more aggressive and persistent repletion with IV calcium, phosphorus, and vitamin D, as well as time for the denosumab to dissipate, the patient’s electrolytes stabilized and he was able to be discharged with oral replacement and close follow-up. Therefore, long-term monitoring of electrolytes for patients on denosumab should be carefully considered.

Hypocalcemia and bone mineral density changes following denosumab treatment in end-stage renal disease patients: a meta-analysis of observational studies

The incidence of hypocalcemia and bone mineral density (BMD) changes in end-stage renal disease (ESRD) patients on denosumab remains unclear. We performed this meta-analysis to assess the incidence of denosumab-associated hypocalcemia and effects of denosumab on BMD in ESRD patients. A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through November 2017 to identify studies evaluating incidence of denosumab-associated hypocalcemia and changes in serum calcium, phosphate, alkaline phosphatase (ALP), parathyroid hormone (PTH), and BMD from baseline to post-treatment course of denosumab in ESRD patients. Study results were pooled and analyzed using a random-effect model. The protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42017081074). Six observational studies with a total of 84 ESRD patients were enrolled. The pooled estimated incidence of hypocalcemia during denosumab treatment was 42% (95% CI 29-55%, I² = 0%). Hypocalcemia occurred approximately 7 to 20 days after the first dose and reached nadir of low calcium levels in the first 2 weeks up to 2 months. However, there were no significant changes in serum calcium or phosphate from baseline to post-treatment course (≥ 3 months after treatment) with mean differences [MDs] of 0.20 mg/dL (95% CI, - 0.30 to 0.69 mg/dL) and - 0.10 mg/dL (95% CI, - 0.70 to 0.49 mg/dL). There were significant reductions in ALP and PTH levels with standardized mean differences (SMDs) of - 0.65 (95% CI - 1.13 to - 0.16) and - 1.89 (95% CI - 3.44 to - 0.34), respectively. There were significant increases in T-scores with MDs of 0.39 (95% CI 0.10 to 0.69) and 0.79 (95% CI 0.60 to 0.98) for lumbar spine and femoral neck, respectively. Our study demonstrates the estimated incidence of denosumab-associated hypocalcemia in dialysis patients of 42%. From baseline to post-treatment course, although there are no differences in serum calcium and phosphate, our findings suggest significant reductions in ALP and PTH and a significant increase in BMD. Currently, denosumab should not be considered as the treatment of choice in ESRD patients until more safety and efficacy data are available.