Critical hypercalcemia following discontinuation of denosumab therapy for metastatic giant cell tumor of bone

Rebound hypercalcemia after denosumab cessation during follow-up after surgical treatment for parathyroid carcinoma: case report and literature review

Denosumab is a potent antiresorptive medication, commonly used in the treatment of osteoporosis, as well as in a variety of other diseases. Potential adverse rebound effects after its cessation include a loss in bone mineral density and an increased risk of osteoporotic fractures. Hypercalcemia is a less frequently reported rebound phenomenon after denosumab discontinuation, that may pose a diagnostic challenge to physicians as a rare non-parathyroid hormone (PTH) dependent cause of hypercalcemia. In our case, a 47-year-old male presented with rebound hypercalcemia after denosumab cessation during follow-up after surgical treatment for parathyroid carcinoma. This non-PTH-dependent hypercalcemia resolved after re-initiation of denosumab. We performed a systematic literature review on rebound hypercalcemia after denosumab cessation and identified 52 individual patient cases. Children appear to be more prone to developing rebound hypercalcemia, which could be attributed to their higher baseline bone turnover, underlying conditions, or denosumab dosage regimens. In most cases, patients initially presented with acute and often severe symptoms of hypercalcemia that occur from 1.75 to 9 months after denosumab cessation (4 to 9 months in adults). Most effective treatment approaches to sufficiently decrease serum calcium levels were bisphosphonates or re-administration of denosumab. A watch and wait strategy may be sufficient in asymptomatic cases, which are less common and probably underdiagnosed. Subsequent antiresorptive treatment after denosumab cessation, which is a common practice in osteoporosis treatment, may reduce the risk of rebound hypercalcemia. As denosumab is a frequently used drug in patients with advanced malignant diseases and rebound hypercalcemia with low PTH levels may raise the suspicion for skeletal metastases, awareness of this rebound effect may be for particular relevance in such settings.

Hypercalcemia in children induced by denosumab: a case report and an analysis of the FDA adverse event reporting system database

BACKGROUND

The potential risks of denosumab on pediatric patients have raised concerns about its safety. This article aims to analyze the adverse effects of denosumab in minors, with a specific focus on hypercalcemia.

RESEARCH DESIGN AND METHODS

A case study involving a child was analyzed. The OpenVigil 2.1 was utilized to extract adverse event data from the FAERS database, focusing on denosumab as the primary suspect drug in pediatric patients. The study also reviewed published cases of children developing hypercalcemia after discontinuing denosumab.

RESULTS

The incidence of denosumab induced hypercalcemia in individuals under 18 years old is significantly higher than the overall incidence. The signal value for hypercalcemia was higher in the male group and was highest in the adolescent group. Hypercalcemia usually appeared approximately 4 months after denosumab discontinuation. Males had a higher peak blood calcium level. Patients aged 0-11 years had a higher average peak serum calcium compared to aged 12-17 years.

CONCLUSIONS

This study highlights the risk of hypercalcemia after discontinuation of denosumab in minors, with young age and male gender identified as potential high-risk factors. These findings offer valuable safety warnings and preventative measures for the secure administration of this drug in pediatric populations.

Management of RANKL-mediated Disorders With Denosumab in Children and Adolescents: A Global Expert Guidance Document

CONTEXT

Denosumab is an effective treatment for many receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated disorders but there are potential safety considerations and limited data to guide its use in children and adolescents.

OBJECTIVE

This document seeks to summarize the evidence and provide expert opinion on safe and appropriate use of denosumab in pediatric RANKL-mediated disorders.

PARTICIPANTS

Ten experts in pediatric bone and mineral medicine from 6 countries with experience in the use of denosumab participated in the creation of this document.

EVIDENCE

Data were sourced from the published literature, primarily consisting of case reports/series and review articles because of the lack of higher level evidence. Expert opinion of the authors was used substantially when no published data were available.

CONCLUSION

Denosumab is an effective treatment for RANKL-mediated disorders in children and adolescents but is often not curative and, in some cases, is best used in conjunction with surgical or other medical treatments. Careful multidisciplinary planning is required to define the goals of treatment and expert oversight needed to manage the risk of mineral abnormalities. Substantive, collaborative research efforts are needed to determine optimal treatment regimens and minimize risks.

Diagnosis and monitoring denosumab therapy of giant cell tumors of bone: radiologic-pathologic correlation

OBJECTIVE

To determine the value of CT and dynamic contrast-enhanced (DCE-)MRI for monitoring denosumab therapy of giant cell tumors of bone (GCTB) by correlating it to histopathology.

MATERIALS AND METHODS

Patients with GCTB under denosumab treatment and monitored with CT and (DCE-)MRI (2012-2021) were retrospectively included. Imaging and (semi-)quantitative measurements were used to assess response/relapse. Tissue samples were analyzed using computerized segmentation for vascularization and number of neoplastic and giant cells. Pearson's correlation/Spearman's rank coefficient and Kruskal-Wallis tests were used to assess correlations between histopathology and radiology.

RESULTS

Six patients (28 ± 8years; five men) were evaluated. On CT, good responders showed progressive re-ossification (+7.8HU/month) and cortical remodeling (woven bone). MRI showed an SI decrease relative to muscle on T1-weighted (-0.01 A.U./month) and on fat-saturated T2-weighted sequences (-0.03 A.U./month). Time-intensity-curves evolved from a type IV with high first pass, high amplitude, and steep wash-out to a slow type II. An increase in time-to-peak (+100%) and a decrease in Ktrans (-71%) were observed. This is consistent with microscopic examination, showing a decrease of giant cells (-76%), neoplastic cells (-63%), and blood vessels (-28%). There was a strong statistical significant inverse correlation between time-to-peak and microvessel density (ρ = -0.9, p = 0.01). Significantly less neoplastic (p = 0.03) and giant cells (p = 0.04) were found with a time-intensity curve type II, compared to a type IV. Two patients showed relapse after initial good response when stopping denosumab. Inverse imaging and pathological findings were observed.

CONCLUSION

CT and (DCE-)MRI show a good correlation with pathology and allow adequate evaluation of response to denosumab and detection of therapy failure.

Denosumab Treatment Does Not Halt Progression of Bone Lesions in Multicentric Carpotarsal Osteolysis Syndrome

Here we report the use of denosumab, a monoclonal antibody against receptor activator of nuclear factor κB ligand (RANKL), as monotherapy for multicentric carpotarsal osteolysis syndrome (MCTO) in an 11.5-year-old male with a heterozygous missense mutation in MAFB (c.206C>T; p.Ser69Leu). We treated the subject with 0.5 mg/kg denosumab every 60-90 days for 47 months and monitored bone and mineral metabolism, kidney function, joint range of motion (ROM), and bone and joint morphology. Serum markers of bone turnover reduced rapidly, bone density increased, and renal function remained normal. Nevertheless, MCTO-related osteolysis and joint immobility progressed during denosumab treatment. Symptomatic hypercalcemia and protracted hypercalciuria occurred during weaning and after discontinuation of denosumab and required treatment with zoledronate. When expressed in vitro, the c.206C>T; p.Ser69Leu variant had increased protein stability and produced greater transactivation of a luciferase reporter under the control of the PTH gene promoter than did wild-type MafB. Based on our experience and that of others, denosumab does not appear to be efficacious for MCTO and carries a high risk of rebound hypercalcemia and/or hypercalciuria after drug discontinuation. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Surgical Management and Denosumab for Aneurysmal Bone Cysts of the Spine in an Australian Tertiary Paediatric Centre

Aneurysmal bone cysts (ABC) are rare osteolytic, benign but often locally aggressive tumours of the long bones or vertebrae. For spinal ABC, surgical management, embolisation or sclerotherapy alone often carry high morbidity and/or high recurrence rates. Interruption of receptor activator of nuclear factor-kappa B ligand (RANKL) signalling holds promise as an effective therapeutic strategy for these tumours. We aimed to review the approach to surgical management and evaluate the efficacy and safety of denosumab for ABC of the spine in children. Retrospective review of 7 patients treated with denosumab using a standardised protocol for ABC of the spine in a tertiary paediatric centre. Surgical intervention was only conducted if there was spinal instability or significant neurological impairment. Denosumab 70 mg/m² was given 4-weekly for at least 6 months, followed by 2 doses of zoledronate 0.025 mg/kg, aiming to prevent rebound hypercalcaemia. All patients achieved stability of the spine and resolution of neurological impairment, if present. Six patients achieved metabolic remission and have ceased denosumab without recurrence to date; the other showed clinical and radiological improvement without complete metabolic remission. Three patients developed symptomatic hypercalcaemia 5-7 months after cessation of denosumab, requiring additional bisphosphonate treatment. We present our algorithm for the surgical and medical management of paediatric spinal ABC. Denosumab produced a radiological and metabolic response in all patients, with complete remission in most. Follow-up time was not long enough to evaluate the endurance of response after cessation in some patients. Incidence of rebound hypercalcaemia in this paediatric cohort was high, prompting a change to our protocol.

Treatment of Hypercalcemia of Malignancy in Adults: An Endocrine Society Clinical Practice Guideline

BACKGROUND

Hypercalcemia of malignancy (HCM) is the most common metabolic complication of malignancies, but its incidence may be declining due to potent chemotherapeutic agents. The high mortality associated with HCM has declined markedly due to the introduction of increasingly effective chemotherapeutic drugs. Despite the widespread availability of efficacious medications to treat HCM, evidence-based recommendations to manage this debilitating condition are lacking.

OBJECTIVE

To develop guidelines for the treatment of adults with HCM.

METHODS

A multidisciplinary panel of clinical experts, together with experts in systematic literature review, identified and prioritized 8 clinical questions related to the treatment of HCM in adult patients. The systematic reviews (SRs) queried electronic databases for studies relevant to the selected questions. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assess the certainty of evidence and make recommendations. An independent SR was conducted in parallel to assess patients' and physicians' values and preferences, costs, resources needed, acceptability, feasibility, equity, and other domains relevant to the Evidence-to-Decision framework as well as to enable judgements and recommendations.

RESULTS

The panel recommends (strong recommendation) in adults with HCM treatment with denosumab (Dmab) or an intravenous (IV) bisphosphonate (BP). The following recommendations were based on low certainty of the evidence. The panel suggests (conditional recommendation) (1) in adults with HCM, the use of Dmab rather than an IV BP; (2) in adults with severe HCM, a combination of calcitonin and an IV BP or Dmab therapy as initial treatment; and (3) in adults with refractory/recurrent HCM despite treatment with BP, the use of Dmab. The panel suggests (conditional recommendation) the addition of an IV BP or Dmab in adult patients with hypercalcemia due to tumors associated with high calcitriol levels who are already receiving glucocorticoid therapy but continue to have severe or symptomatic HCM. The panel suggests (conditional recommendation) in adult patients with hypercalcemia due to parathyroid carcinoma, treatment with either a calcimimetic or an antiresorptive (IV BP or Dmab). The panel judges the treatments as probably accessible and feasible for most recommendations but noted variability in costs, resources required, and their impact on equity.

CONCLUSIONS

The panel's recommendations are based on currently available evidence considering the most important outcomes in HCM to patients and key stakeholders. Treatment of the primary malignancy is instrumental for controlling hypercalcemia and preventing its recurrence. The recommendations provide a framework for the medical management of adults with HCM and incorporate important decisional and contextual factors. The guidelines underscore current knowledge gaps that can be used to establish future research agendas.

Osteoporosis in children and adolescents: how to treat and monitor?

Osteoporosis is a condition of increased bone fragility associated with fractures. Apart from primary genetic osteoporotic conditions, secondary osteoporosis in children is being increasingly recognized. As a result, there is growing interest in its prevention and treatment. Important goals of care are to prevent fractures, increase bone mass and trabecular and cortical thickness, reshape vertebral fractures, prevent (or correct) skeletal deformities, and improve mobility, independence, and quality of life. Secondary pediatric osteoporosis is often of multifactorial origin since affected children frequently have more than one acquired factor that is detrimental to bone health. Typical conditions causing osteoporosis are leukemias, progressive muscle or neurological disorders, as well as chronic inflammatory conditions and their treatment. Management of children with osteoporosis involves a multidisciplinary team involving pediatric experts from different subspecialties. With regard to prevention and early intervention, it is important to provide optimal management of any underlying systemic conditions including avoidance, or dose-reduction, of osteotoxic medications. Basic supporting life-style measures, such as appropriate nutrition, including adequate calcium intake and vitamin D, and physical activity are recommended, where possible. When pediatric treatment criteria for osteoporosis are met, antiresorptive drugs constitute the first pharmacological line treatment.

CONCLUSION

This clinical review focuses on the prevention, treatment, and follow-up of children with, or at risk of developing, osteoporosis and the transition from pediatric to adult care.

WHAT IS KNOWN

• Osteoporosis and associated fractures can cause significant morbidity and reduce the quality of life. • The developing skeleton has huge potential for recovery and reshaping, thus early detection of fractures, assessment of recovery potential, and treatment of children with osteoporosis can prevent future fractures, deformities, and scoliosis, improve function and mobility, and reduce pain.

WHAT IS NEW

• Osteoporosis in children and adolescents requires a multidisciplinary approach with a thorough assessment of recovery potential, and indication for therapy should be personalized. • Although bisphosphonates still represent the drug most commonly used to increase bone mass, improve mobility, and reduce pain and recurrence of fractures, new agents are being developed and could be beneficial in children with specific conditions.

Rebound hypercalcemia post-denosumab cessation in metastatic breast cancer

Denosumab delays and prevents skeletal related events in patients with malignancy-related bony metastases. Rarely, denosumab discontinuation can lead to rebound hypercalcemia in the setting of increased bone resorption. We describe the case of a 49-year-old breast cancer survivor who developed rebound hypercalcemia after cessation of long-term denosumab. She had been treated with 42 doses of denosumab between August 2013 and March 2020 and 8 months after her last dose of denosumab developed symptomatic hypercalcemia. Parathyroid hormone levels were suppressed, and active malignancy was excluded based on biochemical and radiological testing. She required treatment with intravenous bisphosphonates on three separate occasions in order to achieve long-term normalization of her hypercalcemia. Rebound hypercalcemia post-denosumab cessation is a rare but serious complication that clinicians should be aware of.

Unresectable Clival Giant Cell Tumor, Tumor Control With Denosumab After Relapse: A Case Report and Systematic Review of the Literature

Giant cell tumors (GCTs) of the skull base are rare entities. Although considered histologically benign, GCTs are locally aggressive with a high rate of local recurrence. The present case describes a 14-year-old girl with a clival GCT who underwent long-term therapy with denosumab after local relapse. To our knowledge, it is the second case described with a follow-up term >2 years from the start of denosumab and who did not receive any other adjuvant treatment besides denosumab. The patient achieved a local control of the disease. According to the few available data, radical excision with adjuvant therapy helps in long-term control in uncommon sites, such as the skull. However, the definitive treatment is still controversial because of their rarity and few follow-up data. The present case highlights the benefit of denosumab and its safety as long-term therapy and contributes to the existing literature with analysis and evaluation of the management strategies and prognosis.

Denosumab for central giant cell granuloma in an Australian tertiary paediatric centre

BACKGROUND

Central giant cell granulomas (CGCG) are rare osteolytic, benign but often locally aggressive tumours of bone. Surgical curettage may not be possible in extensive lesions and resection carries high morbidity, especially in growing children, and previous medical therapies have had variable efficacy and high recurrence rates. Interruption of receptor activator of nuclear factor-kappa B ligand (RANKL) signalling holds promise as an effective therapeutic strategy for these tumours.

AIMS

To evaluate the efficacy and safety of our protocol for denosumab treatment of CGCG in children.

METHODS

Retrospective review of 4 patients treated with denosumab using a standardised protocol for CGCG in a tertiary paediatric centre. Denosumab 70 mg/m² was given 4-weekly, followed by 2 doses of zoledronate 0.025 mg/kg, aimed at preventing rebound hypercalcaemia.

RESULTS

Treatment of CGCG resulted in metabolic remission in all patients, but recurrence, detected by positron emission tomography (PET), occurred at 6 months in three patients and 12 months in one patient. Three patients developed symptomatic hypercalcaemia 4-5 months and one patient asymptomatic hypercalcaemia 7 months after cessation of denosumab, with 3 requiring additional bisphosphonate treatment.

CONCLUSIONS

Denosumab produced a radiological and metabolic response in our patients, but metabolic recurrence occurred in all patients. PET imaging was effective for monitoring treatment response and early detection of recurrence. Incidence of rebound hypercalcaemia in this paediatric cohort was high. We present proposed changes to our protocol with the aim of producing sustained remission and preventing rebound hypercalcaemia.

Translational Strategies to Target Metastatic Bone Disease

Metastatic bone disease is a common and devastating complication to cancer, confounding treatments and recovery efforts and presenting a significant barrier to de-escalating the adverse outcomes associated with disease progression. Despite significant advances in the field, bone metastases remain presently incurable and contribute heavily to cancer-associated morbidity and mortality. Mechanisms associated with metastatic bone disease perpetuation and paralleled disruption of bone remodeling are highlighted to convey how they provide the foundation for therapeutic targets to stem disease escalation. The focus of this review aims to describe the preclinical modeling and diagnostic evaluation of metastatic bone disease as well as discuss the range of therapeutic modalities used clinically and how they may impact skeletal tissue.

Clinical and Radiologic Response of Central Giant Cell Granuloma to Denosumab: A 6-Year Prospective Observational Study

Central giant cell granuloma (CGCG) is a rare lesion of the jaw occurring in young adults and adolescents. Surgery, the traditional mainstay of therapy, is associated with significant morbidity. Denosumab, a humanised monoclonal antibody to RANKL, is effective in a related entity, giant cell tumour of bone (GCTB), but experience in the more indolent CGCG is limited. This prospective observational study of all denosumab-treated CGCG at a tertiary referral centre (2015-2021) aimed to evaluate the safety, efficacy and recurrence risk using denosumab in CGCG at lower-frequency dosing than used for GCTB. All received standardised, time-limited courses of denosumab 120 mg with stepwise increase in dosing interval based on response. They were followed for up to 75 months using a radiation-minimising protocol: 3-monthly clinical, biochemical and radiological assessment (orthopantomograms, cone beam CT). Eight patients, median age 20.5 years [IQR 6], received 13 initial doses [IQR 10] of denosumab 120 mg. Radiologic response was seen after 5.5 doses [IQR 4.5]: ossification in all and size reduction in three. Recurrence occurred in four of seven completing therapy, observed 12 months post-cessation [IQR 6.5]. Larger baseline size, aggressive subtype and fewer than 12 initial doses were more common in the recurrence group. There was no osteonecrosis of the jaw. Hypocalcaemia occurred in one receiving modified dosing. This study represents the largest, most diverse cohort of denosumab-treated CGCG with the longest follow-up in literature. It demonstrates the efficacy of lower-frequency, time-restricted course of denosumab but highlights the risk of recurrence. Long-term follow-up is critical.

Effect of Denosumab on Bone Health in Adult Patients with Duchenne/Becker Muscular Dystrophy: A Report of 2 Cases

CASE

Duchenne/Becker muscular dystrophy (DMD/BeMD) is caused by a loss of dystrophin leading to muscular weakness. Glucocorticoids are used to delay loss of muscle strength but frequently result in osteoporosis and fractures. Bisphosphonates are the drug of choice, and there are limited data on the efficacy of denosumab. We describe 2 patients who were treated with denosumab and had stable to improved bone density with no side effects.

CONCLUSION

Denosumab can be considered for the treatment of osteoporosis in adults with DMD/BeMD, especially when the response to bisphosphonates is not satisfactory.

Drug Treatment of Low Bone Mass and Other Bone Conditions in Pediatric Patients

Osteoporosis may affect young individuals, albeit infrequently. In childhood, bone mass increases, reaching its peak between the second and third decades; then, after a period of stability, it gradually declines. Several conditions, including genetic disorders, chronic diseases, and some medications, can have an impact on bone homeostasis. Diagnosis in young patients is based on the criteria defined by the International Society for Clinical Densitometry (ISCD), published in 2013. High risk factors should be identified and monitored. Often simple interventions aimed to eliminate the underlying cause, to minimize the negative bone effects linked to drugs, or to increase calcium and vitamin D intake can protect bone mass. However, in selected cases, pharmacological treatment should be considered. Bisphosphonates remain the main therapeutic agent for children with significant skeletal fragility and are also useful in a large number of other bone conditions. Denosumab, an anti-RANKL antibody, could become a potential alternative treatment. Clinical trials to evaluate the long-term effects and safety of denosumab in children are ongoing.

Mechanisms of acute hypercalcemia in pediatric patients following the interruption of Denosumab

PURPOSE

Denosumab is a fully human monoclonal anti-RANK-L antibody that is clinically used to counteract the bone loss induced by exacerbated osteoclast activity. Indeed, its binding to RANK-L prevents the interaction RANK-L/receptor RANK that is essential for osteoclastogenesis and bone resorbing activity. Although there are many medications available to treat bone loss diseases, including bisphosphonates, Denosumab is highly effective since it reduces the bone erosion. The use in pediatric patients is safe. However, some concerns are related to the interruption of the treatment. Indeed, in this study, we reported hypercalcemia in two pediatric patients and alterations of circulating osteoclast precursors.

METHODS

Peripheral Blood Mononuclear Cells (PBMC) were isolated from two pediatric patients with hypercalcemia after Denosumab interruption and from 10 controls. Cytofluorimetric analysis and in vitro osteoclastogenesis experiments were performed.

RESULTS

Increase of CD16^-CD14⁺CD11b⁺ cells was revealed in PBMC from patients reflecting the enhanced in vitro osteoclastogenesis.

CONCLUSION

Our data suggest that precautions must be taken when Denosumab therapy is interrupted and gradual decrease of dose and/or timing of treatment should be performed. To prevent the onset of hypercalcemia that could be in the discontinuation phase, cytofluorimetric analysis of PBMC should be performed to evaluate osteoclast precursors.

LONG-TERM USE OF DENOSUMAB IN GIANT CELL TUMORS AND VERTEBRAL ANEURYSMAL BONE CYSTS

ABSTRACT Introduction: Denosumab is a human monoclonal antibody that binds to the receptor activator of nuclear factor kB (RANKL), it is used in the treatment of Osteoporosis. The Giant Cell Tumor (GCT) and the Aneurysmal Bone Cyst (ABC) use the same RANKL, and for this reason this drug began to be used for its treatment. There is consensus on the use, dose-time and 12-month duration for Denosumab treatment of GCT. Not so for ABC. In unresectable, disabling or recurrent tumors, its use could be for life. The adverse events of the habitual use of the drug are known, but it is not known if these increase with time. The objective of the present work is to identify the possible adverse events of treatment with Denosumab for more than 12 months. Material and Method: Series of cases with a diagnosis of GCT or ABC in spine, treated with Denosumab for more than 12 months. Adverse events are: arthralgia, fatigue, spinal pain, pain in extremities, headache, hypokalaemia, hypocalcemia, osteonecrosis of the jaw, malignant transformation, pathological fractures. Results: Eight patients, 6 TCG and 2 ABC, with a mean age at diagnosis of 25,6 years; presenting a mean treatment of 4.18 years (range 1.7 - 8.7). Of 6 operated patients, 4 had recurrence (2 to 36 months after surgery). One patient had to suspend treatment due to necrosis of the jaw, another hypocalcemia, both returned to treatment when stabilized. Conclusions: A minor adverse event (hypocalcemia) and a major adverse event (jaw bone necrosis) were observed. Level of Evidence IV; Original.

Hypercalcemia following discontinuation of denosumab therapy: A systematic review

Denosumab is a monoclonal antibody that has been approved to treat osteoporosis, skeletal metastasis, and giant cell tumor of bone in skeletally mature patients. Due to its potential adverse effects on normal bone growth, its use has not yet been approved in skeletally immature patients; however, the use of this agent in such patients with overt or dysregulated bone resorptive conditions has been explored in recent years. While most studies have proven the effectiveness of denosumab in controlling the progression of various disorders in skeletally immature patients, they have also revealed that refractory hypercalcemia often follows the discontinuation of denosumab treatment, raising a concern over the use of this agent in these patients. Thus, this study was designed to better understand the pathology of this condition through a systematic review of the published literature. Our analysis suggests that this condition has a potential male predisposition, that there is a correlation between the duration of denosumab treatment and patient age, and that this condition often occurs within 3 months after the last administration of denosumab in skeletally immature patients but is significantly less likely in adults. These results may further underscore that high bone formation and bone turnover rates are critically associated with hypercalcemia after the discontinuation of denosumab. In contrast, given that not all skeletally immature patients develop hypercalcemia, it is probable that other unidentified factors are involved in the pathology of this condition.

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Rebound hypercalcemia often follows denosumab cessation in juveniles.

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Although relatively rare, rebound hypercalcemia can occur in adults.

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Rebound hypercalcemia may have a male predisposition in juveniles.

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Treatment duration of denosumab required to trigger hypercalcemia correlates with age.

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Onset of hypercalcemia is significantly earlier in juveniles than in adults.

The current standing on the use of denosumab in giant cell tumour of the bone

Giant cell tumour of the bone (GCTB) has been classically treated surgically. With the advent of denosumab, there is potential to use it as a targeted therapy to downstage the tumour and control its progression. Like all new therapies, the dosage, duration, and long-term effects of treatment can only be determined over the time through numerous trials and errors. The current recommendation of use of the monoclonal antibody is 3-4 months of neoadjuvant denosumab in patients with advanced GCTB for cases who were not candidates for primary curettage initially, and prolonged use for surgically unsalvageable GCTB. The use of Denosumab in the adjuvant setting to prevent recurrence is not established.

Denosumab-Induced Proximal Myopathy in a Child

Denosumab, a fully humanized monoclonal antibody, has been used for the treatment of osteoporosis, in complications resulting from bone metastatic disease and in giant cell tumor in both adults and skeletally mature adolescents. Denosumab is an inhibitor of the receptor activator of nuclear factor kappa-B ligand and belongs to a new class of antiresorptive medications. We report a unique case of myopathy in a 13-year-old boy prescribed denosumab for enchondromatosis. The boy presented with hypovitaminosis D, elevated parathyroid hormone, suppressed alkaline phosphatase, hypocalcemia, and hypophosphatemia after a single dose of denosumab. Our case points to altered calcium–vitamin D homeostasis induced by denosumab. Myopathy associated with denosumab has not been described previously in children. Early recognition of myopathy and adequate supplementation with calcium–vitamin D may ensure a more favorable clinical outcome.

Multiple Pulmonary Metastases of Recurrent Giant Cell Tumor of Bone with Expression of VEGFR-2 Successfully Controlled by Denosumab and Apatinib: A Case Report and Literature Review

Giant cell tumor of bone (GCTB) is a rare, benign, but locally aggressive bone tumor. It has a high tendency for local recurrence, which may increase the incidence of lung metastasis. Currently, an optimal treatment strategy has not been established because of the rarity of pulmonary metastatic GCTB. Denosumab is the preferred regimen for unresectable metastatic lesions; however, there are no alternative treatment options when patients are resistant to denosumab. Apatinib is a small-molecule tyrosine kinase inhibitor that selectively competes for the vascular endothelial growth factor receptor 2 (VEGFR-2) ATP binding site, and several studies have analyzed the effectiveness of apatinib in advanced or metastatic tumors. However, there is no report of apatinib as an anti-angiogenesis therapy for pulmonary metastatic GCTB to date. Here, we present a case of a 26-year-old female who was diagnosed with recurrent and pulmonary metastatic GCTB. Immunohistochemical (IHC) staining indicated that the tumor cells were positive for VEGFR-2. Denosumab was administered to control the metastases; nevertheless, disease progression was confirmed after four months of treatment. Given the IHC results and rapid disease progression, apatinib was added to the treatment strategy. After 42 months of treatment, the patient showed noticeable symptomatic improvement and considerable tumor shrinkage.

Denosumab for Effective Tumor Size Reduction in Patients With Giant Cell Tumors of the Bone: A Systematic Review and Meta-Analysis

BACKGROUND

Denosumab is a human monoclonal antibody that has been used successfully in the treatment of giant cell tumors of bone. These tumors are rare and, in principle, benign, but they are highly aggressive, locally advanced, osteolytic bone tumors that can metastasize to the lungs. Denosumab is an effective treatment when these tumors cannot be surgically removed or when surgical resection is likely to lead to severe morbidity (eg, loss of limbs or joints). The aim of this systematic review and meta-analysis was to investigate patients with giant cell tumors of bone who experienced tumor progression during treatment with denosumab and to compare them with patients who experienced reduction of their giant cell tumors of bone during treatment with denosumab.

METHODS

Embase, Cochrane Library, and MEDLINE/PubMed databases were searched for trials submitted by January 7, 2020, that reported the efficacy and safety of denosumab in patients with giant cell tumors of bone.

RESULTS

Sixty studies were reviewed, involving a total of 1074 patients who had giant cell tumors of bone and were treated with denosumab. Of the 60 studies, 58% of the patients were from case series studies, 39% from open-label phase II studies, and 3% from case reports. The response rate for denosumab as a treatment for giant cell tumors of bone was 97.5%, with statistical significance (P < .0001). Pain in the limbs was statistically the most common adverse event for denosumab treatment in case series studies (P < .0001). No treatment-related deaths occurred in the reviewed studies.

CONCLUSION

Cumulative evidence supports the addition of surgery to optimal medical therapy with denosumab to reduce tumor size, clinical symptoms, and mortality among patients with giant cell tumors of bone.

Successful denosumab treatment for central giant cell granuloma in a 9-year-old child

BACKGROUND

Denosumab is a nonsurgical treatment option for central giant cell granulomas (CGCG), especially in aggressive lesions.

CASE REPORT

We describe a 9-year-old girl with an aggressive maxillary CGCG successfully treated with denosumab, avoiding a mutilating surgery after intralesional corticosteroid injections failed, and the lesion continued to rapidly grow. During denosumab treatment, she developed a self-limiting area of osteonecrosis in the maxillary alveolar bone, which rapidly resolved after antibiotic therapy. Six months after denosumab discontinuation, a maxillary surgical recontour was performed. Two weeks after surgery, the patient presented vomiting, pallor, dehydration, but no fever. Blood tests revealed severe hypercalcemia and acute renal dysfunction. After discarding thyroid, parathyroid, and adrenal alterations, a diagnosis of severe rebound hypercalcemia after denosumab treatment was made. Treatment consisted of hyperhydration, calcium pamidronate, and methylprednisolone, restoring calcium levels to normal.

CONCLUSION

After 2 years of follow-up, she remains on orthodontic treatment, with no recurrences or other episodes of hypercalcemia.

Giant Cell Tumor of Bone: An Update

PURPOSE OF REVIEW

To highlight the new developments in the management of advanced giant cell tumor of bone, a rare locally aggressive benign tumor, which was traditionally managed with surgery alone by either curettage and local adjuvant therapy, wide resection, or marginal excision. Here, we review the current role of systemic therapy for management of locally advanced or metastatic giant cell tumor of bone (GCTB).

RECENT FINDINGS

The elucidation of the pathophysiology of giant cell tumor of bone, especially with regards to the role of nuclear factor kappa B ligand (RANKL), has led to the Food and Drug Administration (FDA) approval of denosumab in the management of locally advanced or metastatic GCTB. For advanced giant cell tumor where surgical resection alone can cause severe morbidity, the paradigm has shifted from local treatment alone to multidisciplinary management with the consideration of use of denosumab.

Treatment of central giant cell granuloma in children with denosumab

Central giant cell granuloma (CGCG) is a benign but locally aggressive intraosseous lesion of the mandible. Historically, it is treated by curettage or resection. Medical therapy is indicated when surgery is associated with increased morbidity or in adjuvant setting to decrease recurrence. Treatment of CGCG with denosumab, a receptor activator of nuclear factor kappa-beta (RANK) ligand inhibitor, is not well studied, especially in children. Here, we describe our experience with the use of denosumab in the treatment of six children with CGCG. All patients had a favorable response with manageable side effects, which suggests that denosumab is an effective treatment option without increased morbidity.

Response to Denosumab in 2 Children With Recurrent Giant Cell Tumor of the Bone With Pulmonary Metastasis

Giant cell tumor of the bone (GCTB) is an uncommon bone tumor, usually localized, and rarely presents at <20 years of age. Denosumab, a fully human monoclonal antibody against RANKL (receptor activator of nuclear factor κB ligand), is approved for the treatment of unresectable GCTB in skeletally mature individuals. We present a case series of 2 pediatric patients with recurrent GCTB with pulmonary metastasis, with clinical response to denosumab therapy.

Mineral and Bone Consequences of High Dose Denosumab Therapy to Treat an Aneurysmal Bone Cyst, a Child Case Report

Aneurysmal bone cysts (ABCs) are rare benign pseudotumoral bone lesions with potential aggressive behavior due to the extensive destruction of surrounding bone. Traditionally, these tumors were treated with open surgery, but there is more and more a shift to less invasive procedures. In particular, treatment for spinal ABCs is generally unsatisfactory due to the risk of morbidity, neurological impairment and recurrence, and there is a need for innovative therapies. Denosumab has been reported as a useful treatment in giant cell tumors of bone (GCTB), so its efficacy has been tested also in other fibro-osseus lesions affecting children and adolescents, such as spinal aneurysmal bone cysts. The pediatric literature is limited to case reports and small series, all of which highlight the efficacy of this treatment on lesions growth and associated bone pain. Some of these reports have already reported well known side effects associated with denosumab, such as hypocalcemia at the beginning of the treatment, and rebound hypercalcemia at the discontinuation. The latter seems to be more frequent in children and adolescents than in adults, probably due to the higher baseline bone turnover in children. In addition, the use of denosumab in young patients could affect both bone modeling and remodeling, even if the consequences on the growing skeleton have not been reported in detail. Here we describe the case of a spinal ABC diagnosed in an 8-year old young boy which was not accessible to surgery but responded favorably to denosumab. Our aim is to describe the rapid changes in mineral and bone homeostasis in this patient, that required advice from the experts of the European Reference Network (ERN) for rare bone and endocrine diseases.

Hypercalcemia upon denosumab withdrawal in primary hyperparathyroidism: a case report and literature review

Denosumab discontinuation is associated with a rapid increase in bone resorption and a decrease in bone mineral density. Spontaneous vertebral fractures may occur as a side effect of the rebound of bone resorption. Cases of rebound-linked hypercalcemia have also been described, moderate in women with osteoporosis and breast cancer and severe in children receiving oncological doses of denosumab. We report the case of an adult woman with primary hyperparathyroidism and moderate hypercalcemia, treated with denosumab for osteoporosis, who developed severe hypercalcemia and spontaneous vertebral fractures (SVFs) after denosumab discontinuation. An 86-year-old woman with densitometric osteoporosis was treated for 3 years with 60 mg of subcutaneous denosumab every 6 months. She was known to have primary hyperparathyroidism, with a serum albumin-corrected calcium of 2.82 mmol/l (NV 2.15-2.5) at the end of denosumab effect. Nine months after the last denosumab injection, she was hospitalized due to worsening overall health. Clinical evaluation revealed severe hypercalcemia (calcium 3.35 mmol/l). Very high values of bone turnover markers (BTMs) suggested a rebound effect due to denosumab discontinuation. An X-ray showed multiple new SVFs. After injection of denosumab 60 mg, serum calcium rapidly decreased and BTMs were dramatically reduced. A surgical approach by minimally invasive parathyroidectomy allowed for definite resolution of hyperparathyroidism and hypercalcemia. This case suggests that hypercalcemia can be a side consequence of denosumab discontinuation, which can become severe when other causes of hypercalcemia, such as primary hyperparathyroidism, are present.

Integration of denosumab therapy in the management of giant cell tumors of bone

A review of the literature indicated denosumab is gaining favorability in the oncology community, particularly with increasing frequency in GCTB. Will denosumab be the breakthrough GCTB treatment? Here, we provide a pertinent case example, a review of the literature regarding the history and basic science behind the use of denosumab for GCTB, highlight the newest insights into the dosing and duration of treatment, and note advancements in the field.

Long-term follow up after denosumab treatment for osteoporosis - rebound associated with hypercalcemia, parathyroid hyperplasia, severe bone mineral density loss, and multiple fractures: a case report

BACKGROUND

The rebound effect after stopping treatment with denosumab may be associated with rapid loss of the gains in bone mineral density achieved with treatment, high levels of bone remodeling markers, the occurrence of vertebral fractures, and even hypercalcemia.

CASE PRESENTATION

A 64-year-old osteoporotic Caucasian woman suffered from a fracture of her second lumbar vertebra in 2004. From January 2005, she was treated with denosumab for 9 years, with good densitometry results for her hip and lumbar areas, and no fractures over the last 6 years of treatment. Ten months after the treatment with denosumab was stopped, a cascade of vertebral fractures, including some in unusual locations (third thoracic vertebra), and multiple rib fractures in a context of hypercalcemia, suggested possible malignancy. A complete evaluation, including systemic, biological, and biopsy analyses, ruled out this hypothesis. The hypercalcemia was associated with normal plasma phosphate and vitamin D concentrations, and a high parathyroid hormone level, with an abnormal fixation of the lower lobe of the thyroid on sesta-methoxy-isobutyl-isonitrile scintigraphy. Histological analysis of the excised parathyroid tissue revealed hyperplasia. The associated thyroidectomy (goiter) led to the discovery of a thyroid papillary microcarcinoma.

CONCLUSIONS

We consider the consequences of this rebound effect, not only in terms of the major loss of bone density (return to basal values within 3 years) and the multiple disabling fracture episodes, but also in terms of the hypercalcemia observed in association with apparently autonomous tertiary hyperparathyroidism. Several cases of spontaneous reversion have been reported in children, but the intervention in our patient precluded any assessment of the possible natural course. The discovery of an associated thyroid neoplasm appears to be fortuitous. Better understanding of the various presentations of the rebound effect after stopping treatment with denosumab would improve diagnostic management of misleading forms, as in this case. Bisphosphonates could partially prevent this rebound effect.

Denosumab in the treatment of giant cell tumor of the spine. Preliminary report, review of the literature and protocol proposal

BACKGROUND

The interest on the role of Denosumab in the treatment strategy of giant cell tumor of the spine is growing. En bloc resection is considered the Enneking appropriate treatment, but morbidity and functional loss are sometimes unacceptable. Denosumab could play a role as a stand-alone treatment, but also as preoperative treatment or as postoperative after intralesional surgery.

MATERIALS AND METHODS

A cohort of 10 out of 12 cases of spinal GCT consecutively treated with Denosumab are analyzed and discussed compared to the cases reported in the literature. A staging of the radiological effect of the treatment is proposed.

RESULTS

The stand-alone and postoperative treatments are still running (12 to 88 months). One therapy was stopped after 15 months, once a satisfactory local effect was achieved, but the treatment had to be restarted 2 months later due to the recurrence of the erosive images. The new treatment was successful. At 1-year follow-up after the gross total excision followed by postoperative Denosumab treatment, no evidence of local recurrence was found. The preoperative treatment duration ranged from 3 to 24 months. No local recurrence followed the en bloc resections.

CONCLUSIONS

Denosumab alone is effective in relieving pain, increasing the ossification and sometimes reducing the tumor volume. It can be considered an excellent solution in spine GCTs whose surgical treatment cannot be Enneking appropriate or is associated with unacceptable morbidity or loss of functions. It is still impossible to state when to safely stop the treatment. Denosumab also plays a role as preoperative protocol. These slides can be retrieved under Electronic Supplementary Material.

Elevated levels of circulating fibroblast growth factor 23 with hypercalcemia following discontinuation of denosumab

We report a case of a 47-year-old woman with hypercalcemia 6 months after discontinuation of denosumab. She underwent right mastectomy for breast cancer and had received aromatase inhibitor and denosumab therapy for 5 years. Thirst, appetite loss, and bilateral ankle pain began few months after cessation of denosumab. She was admitted to the hospital for hypercalcemia and hyperthyroidism 6 months after the last dose of denosumab. Laboratory investigations revealed hypercalcemia, normophosphatemia, normal renal function, and elevated levels of fibroblast growth factor 23 (FGF-23). Serum tartrate-resistant acid phosphatase 5b and urine N-terminal cross-linked telopeptide of type I collagen were both elevated, and bone scintigraphy revealed increase of whole bone uptake. Radiological examinations showed no recurrence of breast cancer or tumors that secrete intact PTH or FGF-23. Hypercalcemia, which lasted for 1 month, was refractory to discontinuation of the aromatase inhibitor, normalization of thyroid hormone levels, saline hydration, and calcitonin administration, but was effectively treated with zoledronic acid. Abnormal uptake on bone scintigraphy and ankle pain both resolved a few months after treatment, and hypercalcemia has not recurred in the ensuing 2 years. In conclusion, we found elevated levels of circulating FGF-23 with hypercalcemia following the discontinuation of denosumab. FGF-23 might be a surrogate marker for massive bone resorption triggered by discontinuation of long-term denosumab treatment.

A review on osteoclast diseases and osteoclastogenesis inhibitors recently developed from natural resources

Natural products have been investigated as potential candidates of novel therapeutics and play a crucial role in advanced medicinal drugs. Natural resources, including local medicinal plants (especially folk medicinal plants), animals, bacteria, and fungi have been used for more than a century, and are precious gifts from nature, providing potential medicines with high safety. Osteoclast-related diseases, such as osteoporosis, rheumatoid arthritis, Paget's disease, osteoclastoma, and periprosthetic osteolysis, are currently the most common reasons for bone inflammation, pain and fractures, resulting in low quality of life. However, the curative effects of current therapeutic drugs for these osteoclast-related diseases are limited, and long-term treatment is needed. Further, in severe cases, surgical treatments are necessary, which may cause unaffordable expenses and subsequent influences such as neuralgia, mental stress, and even development of cancer. Thus, safer inhibitors and potential drugs with enhanced curative effects and quick relief are needed to treat patients with osteoclast diseases. This review aims to introduce the main osteoclast-related diseases and some of the recently developed naturally sourced inhibitors against osteoclastogenesis, also it is desired to attract people's attention on using widely available natural resources for the evolution of new types of osteoclast inhibitors with minimal or no side-effects upon long-term treatments.

Case Report: Safety and Efficacy of Denosumab in Four Children With Noonan Syndrome With Multiple Giant Cell Lesions of the Jaw

Noonan syndrome is a genetic disorder caused by mutations in the RAS/MAPK pathway. Multiple giant cell lesions are a rare sequelae of disruptions in this pathway, termed Noonan-like multiple giant cell lesions (NL/MGCLs). Medical management of these tumors rather than surgical intervention is preferential as the lesions are benign but locally destructive and recurring. This case series describes four male pediatric patients with Noonan syndrome and multiple giant cell lesions of the jaw treated with denosumab, a monoclonal antibody to receptor activator of nuclear factor kappa B ligand (RANKL), which has been approved for the treatment of malignant giant cell tumors in adults but not evaluated for safety or efficacy in children. All four pediatric patients responded clinically and radiographically to the treatment. Adverse events occurred in a predictable pattern and included hypocalcemia and joint pain during the initiation of treatment and symptomatic hypercalcemia after the cessation of treatment. Growth was not significantly impaired in these skeletally immature patients. This case series demonstrates how a weight-adjusted denosumab dose can effectively treat NL/MGCLs and provides laboratory data for consideration of the timing of monitoring for known side effects.

Hypercalcaemia after treatment with denosumab in children: bisphosphonates as an option for therapy and prevention?

BACKGROUND

Pharmacologic options for treatment of osteolytic diseases especially in children are limited. Although not licensed for use, denosumab, a fully humanized antibody to RANKL, is used in children with good effects. Among others, one possible indication are giant cell tumors and aneurysmatic bone cysts. However, there are reports of severe hypercalcemia during weeks to months after termination of denosumab, that are rarely seen in adults.

METHODS

We collected data of four patients, aged 6-17 years, who experienced severe hypercalcemia after completion of treatment with denosumab for unresectable giant cell tumors of bone or aneurysmal bone cysts and methods of their treatment. The detailed case information were described.

RESULTS

One patient was treated with long-term, high-dose steroid therapy, leading to typical Cushing's syndrome. Another patient was restarted on denosumab repeatedly due to relapses of hypercalcemia after every stop. Finally, in two patients, hypercalcemia ceased definitely after treatment with bisphosphonates. However, several applications were necessary to stabilize calcium levels.

CONCLUSIONS

There is a considerable risk of hypercalcemia as an adverse effect after denosumab treatment in children. Therapeutic and, preferably, preventive strategies are needed. Bisphosphonates seem to be an option for both, but effective proceedings still remain to be established.

Aneurysmal bone cyst: results of an off label treatment with Denosumab

Background

The treatment of aneurysmal bone cysts (ABCs) has evolved and less invasive methods have been tried. Denosumab is a monoclonal antibody which inhibits osteoclasts. It has been shown to be effective in giant cell tumour of bone (GCT) of bone and hence promises some effect also in ABC. We report on 6 patients treated with Denosumab and compare our results to the cases already published.

Methods

Data of 6 patients with ABCs and patients whose treatment included Denosumab were retrospectively analyzed. Denosumab was used at a dose of 120 mg on days 1, 8, 15 and 29, and every 4 weeks thereafter. In some of these patients the dose was reduced at the end of the treatment. Clinical and radiological responses were evaluated.

Results

In 4 female and 2 male patients with a mean age of 17 years (range: 6–30 years) the lesions were located in the sacrum (2), in distal radius, distal femur, talus and pelvis. One of the sacral lesions healed after 12 months and has stayed stable for 3 years since. The second patient received 2 years of therapy with recalcification, but recurred 1 year later and is under renewed therapy. The pelvic lesion improved but recurred. This patient has a 13-years history of intermittent therapy including surgery, two pregnancies and remains in a stable situation. The lesion of the talus did not improve with Denosumab after surgery and was complicated by destruction of the ankle joint with osteoarthritis. Recurrent lesions of the distal femur and the distal radius, previously treated by curettage and bone grafting healed under Denosumab and have remained stable for 2 and 3 years, respectively. One case of severe hypercalcemia was observed in a 7-year old child 6 months after discontinuation of Denosumab.

Conclusion

Denosumab provides a treatment option for ABCs in anatomically critical locations. Adjuvant application might reduce the rate of local recurrence. In young patients, severe rebound hypercalcemia months after discontinuation of Denosumab may occur.

Denosumab for treating aneurysmal bone cysts in children

BACKGROUND

Aneurysmal bone cyst (ABC) is a benign tumour whose progression involves the RANK/RANKL signalling pathway. Surgery is the reference standard treatment but carries risks that vary with the site of the tumour. Denosumab is a human monoclonal IgG2 antibody that targets the RANK/RANKL pathway and may therefore hold promise for inhibiting ABC progression. The objective of this study was to evaluate denosumab use in paediatric patients (younger than 18 years) with ABC and to describe the clinical and radiological outcomes, as well as the side effect profile.

HYPOTHESIS

Denosumab is a viable option in children with ABC refractory to standard treatments.

MATERIAL AND METHODS

We retrospectively reviewed the medical files of paediatric patients given denosumab to treat ABC in any of 32 centres affiliated with the French Paediatric Cancer Society (Société Française du Cancer de l'Enfant, SFCE) and French Sarcoma Group (Groupe Sarcome Français, GSF-GETO). We identified 5 patients treated between March 2015 and June 2018. Median age was 8 years (range, 7-17 years). Pain was a symptom in all 5 patients and neurological deficits were present in 3 patients. Surgery was performed in 4 patients, either before (n=3) or after (n=1) denosumab therapy; the remaining patient had no surgery. Denosumab was given as monthly injections in a dosage of 70mg/m² for a median of 12 months (range, 4-23 months). The clinical outcomes and changes in computed tomography and/or magnetic resonance imaging findings were evaluated.

RESULTS

Abnormalities in calcium and phosphate levels secondary to the ABC occurred in 2 patients. At median of 24 months (range, 0-28 months) after denosumab initiation, all 5 patients were free of pain, and the neurological deficits in 3 patients had improved. Central remineralisation and cortical reconstitution were demonstrated consistently by the imaging studies.

DISCUSSION

Denosumab is a viable treatment option in selected paediatric patients with inoperable ABC. The immediate adverse effect profile is acceptable. A larger study with a longer follow-up would be welcome to further assess the contribution of denosumab to the treatment of ABC.

LEVEL OF EVIDENCE

IV.

Acute hypercalcemia and excessive bone resorption following anti-RANKL withdrawal: Case report and brief literature review

Denosumab is an anti-RANKL antibody that is commonly used for the treatment of osteoporosis; in oncology, bisphosphonates and denosumab have become the standard therapies for the treatment and prevention of skeletal complications in patients with myeloma and solid tumors. In recent years, excessive bone remodeling following the discontinuation of denosumab has raised concerns. Several cases of hypercalcemia have been reported after the discontinuation of high-dose denosumab (120 mg every 4 weeks), mainly in children. In this study, we report a new case of severe refractory hypercalcemia in a 54-year-old woman who received high-dose denosumab for 5 years as an adjuvant therapy for breast cancer. She is currently in remission and undergoing treatment with anastrazole, an aromatase inhibitor. The peculiarities of this case are the presence of associated bone pain with subperiosteal bone resorption on hand X-rays, and diffuse, long bone diaphyseal uptake on a bone scan. Hyperparathyroidism has been ruled out, and existing evidence suggests that this high-level of bone remodeling could be due to a rebound hyperactivation of the RANKL pathway. In addition to rehydration, repeated use of i.v. bisphosphonates was required to control recurrent hypercalcemia. As hypercalcemia is a serious metabolic complication, a gradual dose reduction should be considered when interruption of high dose denosumab therapy is planned.

Spontaneous vertebral fractures after denosumab discontinuation: A case collection and review of the literature

OBJECTIVE

Denosumab is an antiresorptive drug with demonstrated efficacy in the treatment of osteoporosis. However, discontinuation of this agent is associated with increased bone turnover and rapid bone loss, and more recently, with the development of vertebral fractures (VF) in some patients. Therefore, the aim of the study was to analyze the clinical characteristics, bone metabolism parameters and evolution of a group of patients who developed vertebral fractures after denosumab discontinuation. In addition, we reviewed the literature on this subject.

METHODS

During a period of 28 months (September 2015-January 2018) 7 women presenting spontaneous vertebral fractures after denosumab discontinuation were attended in the Rheumatology Department of our centre. We analyzed their clinical characteristics, bone metabolism parameters and evolution and reviewed the literature related to this subject.

RESULTS

The patients had received denosumab during 24-58 months (median 38), and developed a median of 5 VF per patient at 8-20 months (median 10) since the last dose of denosumab. Only 2 patients presented previous VF, and most (5 patients) received previous bisphosphonate treatment. After VF all restarted antiosteoporotic treatment with no further fractures during follow-up (median 19 months).

CONCLUSIONS

In this short series, previous bisphosphonate treatment does not seem to be a protective factor for the development of VF. The possible development of VF following discontinuation of denosumab must be taken into account in the clinical practice of physicians and dentists. Nonetheless, further studies are needed to improve the identification of patients at risk and the most adequate sequential treatment options.

Mechanisms that drive bone pain across the lifespan

Disorders of the skeleton are frequently accompanied by bone pain and a decline in the functional status of the patient. Bone pain occurs following a variety of injuries and diseases including bone fracture, osteoarthritis, low back pain, orthopedic surgery, fibrous dysplasia, rare bone diseases, sickle cell disease and bone cancer. In the past 2 decades, significant progress has been made in understanding the unique population of sensory and sympathetic nerves that innervate bone and the mechanisms that drive bone pain. Following physical injury of bone, mechanotranducers expressed by sensory nerve fibres that innervate bone are activated and sensitized so that even normally non-noxious loading or movement of bone is now being perceived as noxious. Injury of the bone also causes release of factors that; directly excite and sensitize sensory nerve fibres, upregulate proalgesic neurotransmitters, receptors and ion channels expressed by sensory neurons, induce ectopic sprouting of sensory and sympathetic nerve fibres resulting in a hyper-innervation of bone, and central sensitization in the brain that amplifies pain. Many of these mechanisms appear to be involved in driving both nonmalignant and malignant bone pain. Results from human clinical trials suggest that mechanism-based therapies that attenuate one type of bone pain are often effective in attenuating pain in other seemingly unrelated bone diseases. Understanding the specific mechanisms that drive bone pain in different diseases and developing mechanism-based therapies to control this pain has the potential to fundamentally change the quality of life and functional status of patients suffering from bone pain.

The Changing Sensory and Sympathetic Innervation of the Young, Adult and Aging Mouse Femur

Although bone is continually being remodeled and ultimately declines with aging, little is known whether similar changes occur in the sensory and sympathetic nerve fibers that innervate bone. Here, immunohistochemistry and confocal microscopy were used to examine changes in the sensory and sympathetic nerve fibers that innervate the young (10 days post-partum), adult (3 months) and aging (24 months) C57Bl/6 mouse femur. In all three ages examined, the periosteum was the most densely innervated bone compartment. With aging, the total number of sensory and sympathetic nerve fibers clearly declines as the cambium layer of the periosteum dramatically thins. Yet even in the aging femur, there remains a dense sensory and sympathetic innervation of the periosteum. In cortical bone, sensory and sympathetic nerve fibers are largely confined to vascularized Haversian canals and while there is no significant decline in the density of sensory fibers, there was a 75% reduction in sympathetic nerve fibers in the aging vs. adult cortical bone. In contrast, in the bone marrow the overall density/unit area of both sensory and sympathetic nerve fibers appeared to remain largely unchanged across the lifespan. The preferential preservation of sensory nerve fibers suggests that even as bone itself undergoes a marked decline with age, the nociceptors that detect injury and signal skeletal pain remain relatively intact.

Solitary juvenile xanthogranuloma in the spine pretreated with neoadjuvant denosumab therapy followed by surgical resection in a 5-year-old child: case report and literature review

PURPOSE

We present a case report that describes neoadjuvant denosumab therapy initiated in a child with a solitary giant cell-rich juvenile xanthogranuloma tumor involving the spine, and review the current literature.

METHODS

A giant cell-rich histiocytic lesion involving the 11th thoracic vertebral body was identified in a healthy 5-year-old girl with persistent back and pelvic pain for several months. Imaging examinations and an open biopsy were performed to obtain a definite pathologic diagnosis. As the tumor appeared to be aggressive in nature, we administered adjuvant therapy with denosumab preoperatively and then performed a total spondylectomy.

RESULTS

Histopathology confirmed that the tumor was juvenile xanthogranuloma. No tumor metastases or recurrence were detected at the 3-year follow-up, and the patient was asymptomatic.

CONCLUSIONS

In giant cell-rich tumors, denosumab is occasionally used as neoadjuvant or adjuvant therapy, especially for tumors in difficult locations or with substantial soft tissue extensions. Rare adverse events in children include skin infections and disruption of calcium homeostasis. Surgical treatment is aimed at removing the tumor and relieving the symptomatic spinal cord compression. Use of denosumab as neoadjuvant therapy for juvenile xanthogranuloma involving the spine has not been reported previously.

Osteonecrosis of the Jaw and Rebound Hypercalcemia in Young People Treated With Denosumab for Giant Cell Tumor of Bone

CONTEXT

Denosumab, an inhibitor of receptor activator of nuclear factor κ-B ligand, is an approved treatment of giant cell tumor of bone (GCTB) in adults and "skeletally mature" adolescents. Safety concerns include oversuppression of bone remodelling, with risk of osteonecrosis of the jaw (ONJ) and atypical femur fractures during treatment in adults and rebound hypercalcemia after treatment cessation in children. To date, ONJ has never been reported in children or adolescents.

OBJECTIVES

To describe serious adverse effects during and following high-dose denosumab therapy in GCTB patients.

PATIENTS

Two adolescents (14 and 15 years) and a young adult (40 years) received fixed-dose denosumab for GCTB for 1.3 to 4 years (cumulative dose, 47 to 98 mg/kg), which was stopped because of development of ONJ in one adolescent and bilateral femoral cortical stress reactions in the young adult. All three patients developed rebound hypercalcemia with acute kidney injury 5.5 to 7 months after denosumab cessation.

RESULTS

The ONJ necessitated surgical debridement. Rebound hypercalcemia (serum calcium, 3.1 to 4.3 mmol/L) was unresponsive to hyperhydration alone, requiring repeated doses of calcitonin or intravenous bisphosphonate treatment. Hypercalcemia recurred in two patients within 4 weeks, with normal serum calcium profiles thereafter. All patients were naive to chemotherapy, radiotherapy, bisphosphonates, and corticosteroids and were metastases free, confirming the causative role of denosumab in these complications.

CONCLUSION

These suppression-release effects of high-dose denosumab on bone remodeling raise questions about safety of fixed dosing and treatment duration. In young people, weight-adjusted dosing and safety monitoring during and after antiresorptive therapy is required.

Monoclonal antibodies for treating osteoporosis

INTRODUCTION

Osteoporosis is the most widespread skeletal disease requiring innovative therapeutic strategies for its management. The understanding of receptor activator of nuclear factor kappa-B ligand (RANKL) and sclerostin's role in bone cell biology is completely changing the therapeutic landscape. RANKL supports osteoclast formation and activity and is mainly produced by cells of osteoblastic lineage. Sclerostin, an antagonist of the Wnt pathway, has a key role in bone formation and is mainly secreted by osteocytes. High levels of RANKL and sclerostin have been detected in osteoporosis, leading to the production of antibodies able to neutralize their activity.

AREAS COVERED

In this review, the authors give an overview and discuss the literature and data on denosumab and romosozumab to treat osteoporosis. Clinical studies indicate that long-term treatment with denosumab causes a continuous increase in bone mineral density with low incidence of adverse effects. Romosozumab treatment gives increases bone formation and improves bone mineral density (BMD) though further studies are needed to better evaluate the adverse effects.

EXPERT OPINION

Denosumab and romosozumab show promise in the treatment of osteoporosis. Furthermore, their different mechanisms of action compared to existing anti-osteoporotic drugs may permit alternative strategies for osteoporosis treatment down the line

Denosumab: an Emerging Therapy in Pediatric Bone Disorders

PURPOSE OF REVIEW

Denosumab is an inhibitor of receptor activator of nuclear factor kappa-B ligand (RANKL), and has emerged as an important novel therapy for skeletal disorders. This article examines the use of denosumab in children.

RECENT FINDINGS

Considerable safety and efficacy data exists for denosumab treatment of adults with osteoporosis, bone metastases, and giant cell tumors. Pediatric data is limited; however, evidence suggests denosumab may be beneficial in decreasing bone turnover, increasing bone density, and preventing growth of certain skeletal neoplasms in children. Denosumab's effect on bone turnover is rapidly reversible after drug discontinuation, representing a key difference from bisphosphonates. Rebound increased bone turnover has led to severe hypercalcemia in several pediatric patients. Denosumab is a promising therapy for pediatric skeletal disorders. At present, safety concerns related to rebounding bone turnover and mineral homeostasis impact use of denosumab in children. Research is needed to determine if and how these effects can be mitigated.

Biological effects of anti-RANKL antibody administration in pregnant mice and their newborns

Denosumab, a fully human monoclonal antibody that neutralizes receptor activator of nuclear factor-κB ligand (RANKL) and blocks osteoclast differentiation, has received approval in Japan for use as an anti-resorptive drug for osteoporosis and skeletal-related events (SREs) in patients with solid cancer. Denosumab is contraindicated during pregnancy, though the effects of blocking RANKL activity on pregnant mothers and their newborns are unclear. We used mice to investigate the effects of an anti-RANKL antibody on maternal and newborn health. Mothers injected with the anti-RANKL antibody had increased bone mass as compared with the controls, while osteoclast number and the level of tartrate-resistant acid phosphatase (TRAP) in serum were increased at the end of pregnancy. Newborn mice exposed to the antibody in utero were normally born, but showed increased bone mass and died within 48 h after birth. None of the newborns were found to have milk in their stomachs, suggesting that they died due to a maternal defect in lactation. Consistent with this, anti-RANKL antibody-injected mothers displayed impaired mammary gland development. However, fostering by healthy surrogate mothers rescued only 33% of the antibody-exposed newborns, suggesting that neonatal mortality was due, at least in part, to an intrinsic defect in the newborns. Our findings show that anti-RANKL antibody administration during pregnancy results in not only an undesirable increase in bone mass, but also has harmful effects on newborn survival.

Denosumab: Current Use in the Treatment of Primary Bone Tumors

Denosumab, a human monoclonal antibody that inhibits bone resorption by binding on the receptor activator of the nuclear factor kappa-β ligand, has recently emerged as an additional option in the treatment of musculoskeletal osteolytic tumors. This article focuses on the recent literature regarding the effectiveness of denosumab in the management of giant cell tumor, multiple myeloma, aneurysmal bone cyst, and osteosarcoma. The mechanism of action of denosumab in the management of these tumors and the associated side effects are discussed in detail. [ Orthopedics. 2017; 40(4):204-210.].

Denosumab Therapy for Giant Cell Tumor of Bone Pulmonary Metastasis

Case

A 68-year-old female was diagnosed with giant cell tumor of bone (GCTB) metastatic to her lungs. The patient was treated with IV denosumab for the course of 4.5 years for these metastases. The metastatic tumor burden decreased significantly after only 3 months of therapy. The size of the metastases has been stable for over 4 years.

Conclusion

Denosumab therapy has promise in the treatment of GCTB, including pulmonary metastasis. However, the long-term role of denosumab for pulmonary metastases is yet to be determined.