Denosumab in Giant Cell Tumor of Bone: Current Status and Pitfalls

Efficacy and safety of denosumab de‑escalation in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is a locally aggressive intermediate bone tumor. Denosumab has shown effectiveness in GCTB treatment; however, the benefits of denosumab de-escalation for unresectable GCTB have not been well discussed. The present study investigated the efficacy and safety of denosumab de-escalation for GCTB. The medical records of 9 patients with unresectable GCTB or resectable GCTB not eligible for resection, who received de-escalated denosumab treatment at Okayama University Hospital (Okayama, Japan) between April 2014 and December 2021, were retrospectively reviewed. The denosumab treatment interval was gradually extended to every 8, 12 and 24 weeks. The radiographic changes and clinical symptoms during standard and de-escalated denosumab therapy were assessed. The denosumab interval was de-escalated after a median of 12 months of a standard 4-weekly treatment. Imaging showed that the re-ossification of osteolytic lesions obtained with the 4-weekly treatment were sustained with 8- and 12-weekly treatments. The extraskeletal masses reduced significantly with standard treatment, while tumor reduction was sustained during de-escalated treatment. During the 24-weekly treatment, 2 patients remained stable, while 2 patients developed local recurrence. The clinical symptoms improved significantly with standard treatment and remained improved during de-escalated treatment. There were severe adverse events including osteonecrosis of the jaw (2 patients), atypical femoral fracture (1 patient) and malignant transformation of GCTB (1 patient). In conclusion, 12-weekly de-escalated denosumab treatment showed clinical benefits as a maintenance treatment in patients with unresectable GCTB, in addition to sustained stable tumor control and improved clinical symptoms with standard treatment. A 24-weekly treatment can also be administered, with careful attention paid to detecting local recurrence.

The tumor-stroma ratio in giant cell tumor of bone: associations with the immune microenvironment and responsiveness to denosumab treatment

BACKGROUND

Currently, there is limited understanding regarding the clinical significance of the tumor-stroma ratio (TSR) in giant cell tumor of bone (GCTB). Hence, we aimed to investigate the distribution of TSR in GCTB and explore its correlation with various clinicopathologic factors, immune microenvironment, survival prognosis, and denosumab treatment responsiveness.

METHODS

We conducted a multicenter cohort study comprising 426 GCTB patients treated at four centers. TSR was evaluated on hematoxylin and eosin-stained and immunofluorescent sections of tumor specimens. Immunohistochemistry was performed to assess CD3+, CD4+, CD8+, CD20+, PD-1+, PD-L1+, and FoxP3+ TIL subtypes as well as Ki-67 expression levels in 426 tissue specimens. These parameters were then analyzed for their correlations with patient outcomes [local recurrence-free survival (LRFS) and overall survival (OS)], clinicopathological features, and denosumab treatment responsiveness.

RESULTS

Low TSR was significantly associated with poor LRFS and OS in both cohorts. Furthermore, TSR was also correlated with multiple clinicopathological features, TIL subtype expression, and denosumab treatment responsiveness. TSR demonstrated similar predictive capabilities as the conventional Campanacci staging system for predicting patients' LRFS and OS.

CONCLUSION

The results of this study provide evidence supporting the use of TSR as a reliable prognostic tool in GCTB and as a predictor of denosumab treatment responsiveness. These findings may aid in developing individualized treatment strategies for GCTB patients in the future.

The Role of Denosumab Treatment in Recurrent Giant Cell Bone Tumor of the Orbit

Giant cell tumor of the bone (GCTB) is a rare primary bone neoplasm, representing about 5% of all primary bone tumors. Most GCTBs are found in the epiphysis of long bones, with only 2% of GCTBs involving the skull. In recent years, the receptor activator of nuclear factor Kappa ligand monoclonal antibody denosumab has been demonstrated as a promising therapeutic option for GCTB; however, this is an evolving field. We present a case of a 57-year-old female with a rare GCTB in the right orbit and sinuses, originally thought to be an aneurysmal bone cyst. Her symptoms included proptosis, intermittent blurry vision, sinus congestion, and frontal headaches. After excision, the tumor recurred within 18 months. Upon repeat excision, a diagnosis of GCTB was made. The patient started denosumab therapy and had no tumor growth over the ensuing 2 years, with stability of symptoms and clinical signs on follow-up.

Thoracic giant cell tumor after two total en bloc spondylectomies including one emergency surgery: A case report

BACKGROUND

For patients with acute paraplegia caused by spinal giant cell tumor (GCT) who require emergency decompressive surgery, there is still a lack of relevant reports on surgical options. This study is the first to present the case of an acute paraplegic patient with a thoracic spinal GCT who underwent an emergency total en bloc spondylectomy (TES). Despite tumor recurrence, three-level TES was repeated after denosumab therapy.

CASE SUMMARY

A 27-year-old female patient who underwent single-level TES in an emergency presented with sudden severe back pain and acute paraplegia due to a thoracic spinal tumor. After emergency TES, the patient's spinal cord function recovered, and permanent paralysis was avoided. The postoperative histopathological examination revealed that the excised neoplasm was a rare GCT. Unfortunately, the tumor recurred 9 months after the first surgery. After 12 months of denosumab therapy, the tumor size was reduced, and tumor calcification. To prevent recurrent tumor progression and provide a possible cure, a three-level TES was performed again. The patient returned to an active lifestyle 1 month after the second surgery, and no recurrence of GCT was found at the last follow-up.

CONCLUSION

This patient with acute paraplegia underwent TES twice, including once in an emergency, and achieved good therapeutic results. TES in emergency surgery is feasible and safe when conditions permit; however, it may increase the risk of tumor recurrence.

Giant cell tumor of bone and secondary osteoarthritis

Giant cell tumor of bone is a commonly encountered aggressive epiphyseal bone tumor, most often treated surgically. The natural history and presentation are classically described but the histopathology is poorly understood. Intralesional curettage is the mainstay of treatment, but there is significant variation in the use of adjuvant and cavity filling modalities. No gold standard has been agreed upon for treatment, and a variety of techniques are currently in use. Given its location, secondary osteoarthritis is a known long-term complication. This review examines the natural history of giant cell tumors, treatment options and complications, and subsequent development of osteoarthritis. Arthroplasty is usually indicated for secondary osteoarthritis although data is limited on its efficacy. Further directions will likely center on improved pharmacological treatments as well as improved arthroplasty techniques.

Establishment and characterization of two novel patient-derived cell lines from giant cell tumor of bone: NCC-GCTB8-C1 and NCC-GCTB9-C1

Giant cell tumor of bone (GCTB) is a rare osteolytic bone tumor consisting of mononuclear stromal cells, macrophages, and osteoclast-like giant cells. Although GCTB predominantly exhibits benign behavior, the tumor carries a significant risk of high local recurrence. Furthermore, GCTB can occasionally undergo malignant transformation and distal metastasis, making it potentially fatal. The standard treatment is complete surgical resection; nonetheless, an optimal treatment strategy for advanced GCTB remains unestablished, necessitating expanded preclinical research to identify appropriate therapeutic options. However, only one GCTB cell line is publicly available from a cell bank for research use worldwide. The present study reports the establishment of two novel cell lines, NCC-GCTB8-C1 and NCC-GCTB9-C1, derived from the primary tumor tissues of two patients with GCTB. Both cell lines maintained the hallmark mutation in the H3-3A gene, which is associated with tumor formation and development in GCTB. Characterization of these cell lines revealed their steady growth, spheroid-formation capability, and invasive traits. Potential therapeutic agents were identified via extensive drug screening of the two cell lines and seven previously established GCTB cell lines. Among the 214 antitumor agents tested, romidepsin, a histone deacetylase inhibitor, and mitoxantrone, a topoisomerase inhibitor, were identified as potential therapeutic agents against GCTB. Conclusively, the establishment of NCC-GCTB8-C1 and NCC-GCTB9-C1 provides novel and crucial resources that are expected to advance GCTB research and potentially revolutionize treatment strategies.

Systematic analysis of RNA-binding proteins identifies targetable therapeutic vulnerabilities in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor with a strong tendency to metastasize, limiting the prognosis of affected patients. Genomic, epigenomic and transcriptomic analyses have demonstrated the exquisite molecular complexity of this tumor, but have not sufficiently defined the underlying mechanisms or identified promising therapeutic targets. To systematically explore RNA-protein interactions relevant to OS, we define the RNA interactomes together with the full proteome and the transcriptome of cells from five malignant bone tumors (four osteosarcomata and one malignant giant cell tumor of the bone) and from normal mesenchymal stem cells and osteoblasts. These analyses uncover both systematic changes of the RNA-binding activities of defined RNA-binding proteins common to all osteosarcomata and individual alterations that are observed in only a subset of tumors. Functional analyses reveal a particular vulnerability of these tumors to translation inhibition and a positive feedback loop involving the RBP IGF2BP3 and the transcription factor Myc which affects cellular translation and OS cell viability. Our results thus provide insight into potentially clinically relevant RNA-binding protein-dependent mechanisms of osteosarcoma.

Giant Cell Tumor of Patella with Secondary Aneurysmal Bone Cyst-A Rare Case Report of Anterior Knee Pain in Young Adults

Introduction

Primary bone tumors of the patella are rare, with an incidence as low as 0.12%. The majority are benign, with giant cell tumors (GCT) being the predominant tumor affecting this sesamoid bone. An associated secondary aneurysmal bone cyst (ABC) component with a primary patellar GCT is rarely seen.

Case Report

We report a case of a 20-year-old male with long-standing anterior knee pain for 9 months. Having visited multiple clinics and found no relief, the patient presented to us at our out-patient department. Clinical examination suggested patellar tenderness, and knee radiographs showed a lytic lesion with cortical erosions. Computed tomography and magnetic resonance imaging were suggestive of GCT. A patellectomy with a good extensor repair was performed. A patellar biopsy revealed a mixed picture of a primary GCT with a secondary ABC. The patient was closely followed up, and at 12 months, he recovered completely and recorded an excellent functional outcome.

Conclusion

With the incidence of bone tumors on the rise, one should be aware of this relatively rare cause of anterior knee pain. A simple radiograph will help in early diagnosis and will go a long way toward better salvage procedures than more radical procedures like patellectomy.

[Giant cell tumor of bone-an update]

In the past few years, numerous new insights have been gained in the field of giant cell tumor of bone (GCTB). On the one hand, the detection of the highly characteristic histone mutation in the H3F3A gene in GCTB is becoming increasingly important in diagnostics in differentiating GCTB from other giant cell-rich lesions of bone as well as for defining rare variants of GCTB without osteoclastic giant cells. On the other hand, the effects of the H3F3A mutation were shown to have an impact on the epigenetic profile of tumor-driving stromal cells, providing new insights into tumorigenesis of GCTB.

Non‑surgical outcomes and risk factors for pulmonary metastasis from giant cell tumor of bone

The present study detailed four factors associated with an increased risk of pulmonary metastasis, age, pathological fracture, local recurrence and mode of treatment. Local recurrence and pathological fracture were independent risk factors for developing metastasis. From January 2016 to December 2021, data from 50 patients diagnosed with giant cell tumor of bone (GCTB) treated in Khon Kaen Hospital, Thailand, were retrospectively analyzed. The risk factors, including age at diagnosis, location of GCTB, clinical presentation, Campanacci stage and no. of local recurrences, for GCTB-induced pulmonary metastasis were evaluated using univariate and multivariable logistic regression analyses. Of the 50 patients analyzed, 9 patients (18%), with a mean age of 46.3 years (range, 18-68 years), developed pulmonary metastasis. No patients died from pulmonary metastasis in the present study. Statistically significant associations were observed between the development of metastasis and both clinical fracture [odds ratio (OR), 6.107; 95% confidence interval (CI), 1.08-34.70] and local recurrence (OR, 6.48; 95% CI, 1.03-40.87). Patients presenting with both a clinical fracture and local tumor recurrence require more rigorous clinical observation due to the significantly elevated risk of disease progression.

Denosumab for giant cell tumors of bone from 2010 to 2022: a bibliometric analysis

Giant cell tumors of the bone (GCTB) are considered moderately malignant bone tumors. Denosumab, as a neoadjuvant therapy, provides new possibilities for treating GCTB. However, even after multiple studies and long-term clinical trials, there are limitations in the treatment process. Research data and Medical Subject Headings terms related to denosumab and GCTB were collected from January 2010 to October 2022 using the Web of Science and MeSH ( https://meshb.nlm.nih.gov ) browsers. These data were imported into CiteSpace and VOSviewer softwares for bibliometric analysis. Overall, 445 publications on denosumab and GCTB were identified. Over the last 12 years, the growth rate of the total number of publications has remained relatively stable. The USA published the highest number of articles (83) and had the highest centrality (0.42). Amgen Inc. and Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) First Ortoped Rizzoli were identified as the most influential institutions. Many authors have made outstanding contributions to this field. Lancet Oncology had the highest journal impact factor (54.433). Local recurrence and drug dosage are current research hotspots, and future development trends will mainly focus on prognostic markers of GCTB and the development of new therapies. Further research is required to analyze denosumab's safety and efficacy and understand its local recurrence of GCTB, to identify the optimal dose. Future progress in this field will likely focus on exploring new diagnostic and recurrence markers to monitor disease progression and examine new therapeutic targets and treatment strategies.

Conversion in a Resectable Tumor after Denosumab Neoadjuvant in a Large Dorsal Giant Cells Tumor: A Case Report and a Literature Review

Giant cell tumors of bone are a rare entity, usually occurring in young patients and characteristically arising in the long bones. The spinal location is rare and usually presents with pain and/or neurological symptoms. The treatment of choice is surgery. Treatment with Denosumab, a bisphosphonate inhibitor of RANK-L, which is highly expressed in these tumors, has shown extensive activity in unresectable patients or those undergoing incomplete surgery. Preoperative treatment with this drug is gaining increasing interest, as its high potency in tumor reduction in this subtype of neoplasm has allowed resectability in selected patients. We present the case of a young patient with a large spinal tumor who, after neoadjuvant Denosumab, underwent complete en bloc surgery with clean margins and a great pathological response.

Partial sternectomy with reconstruction of a giant cell tumor of the sternum, a case report, Saudi, Arabia

BACKGROUND

Giant cell tumor (GCT) is a relatively common and locally aggressive benign bone tumor that rarely affects the sternum.

CASE PRESENTATION

We report a case of giant cell tumor of the sternum in a 28-year-old Saudi with painful swelling at the lower part of the sternum. Subtotal sternectomy and reconstruction with a neosternum using two layers of proline mesh, a methyl methacrylate prosthesis, and bilateral pectoralis muscle advancement flaps were performed.

CONCLUSIONS

Giant cell tumor of the sternum is a rare diagnosis. Surgical resection with negative margins is the ideal management. To avoid defects or instability of the chest wall, reconstruction of the chest wall with neosternum should be considered.

Investigation of Giant Cell Tumor of Bone and Tissue Engineering Approaches for the Treatment of Giant Cell Tumor of Bone

Primary bone tumors such as Ewing sarcoma, osteosarcoma, and chondrosarcoma, secondary bone tumors developed from progressive malignancies, and metastasized bone tumors are more prevalent and studied descriptively through biology and medical research. Less than 0.2% of cancer diagnoses are caused by rare bone-originating tumors, which despite being rare are particularly difficult due to their high death rates and substantial disease burden. A giant cell tumor of bone (GCTB) is an intramurally invasive but rare and benign type of bone tumor, which seldom metastasizes. The most often prescribed medication for GCTB is Denosumab, a RANKL (receptor activator of nuclear factor κB ligand) inhibitor. Because pharmaceutical drug companies rely on two-dimensional and animal models, current approaches for investigating the diverse nature of tumors are insufficient. Cell line based medication effectiveness and toxicity studies cannot predict tumor response to antitumor medicines. It has already been investigated in detail why molecular pathways do not reproduce in vitro, a phenomenon known as flat biology. Due to physiological differences between human beings and animals, animal models do not succeed in identifying side effects of the treatment, emulating metastatic growth, and establishing the link between cancer and the immune system. This review summarizes and discusses GCTB, the disease, its cellular composition, various bone tumor models, and their properties and utilization in research. As a result, this study delves deep into in vitro testing, which is vital for scientists and physicians in various fields, including pharmacology, preclinical investigations, tissue engineering, and regenerative medicine.

Ischiopubic Ramus Resection as Treatment for Giant Cell Tumor of the Bone: Surgical Techniques in Two Clinical Cases

Giant cell tumors (GCTs) of the ischium are rare and often diagnosed at an advanced stage. In fact, there is no defined treatment algorithm to treat this lesion. We present two case reports of Campanacci's stage three ischiopubic GCT confirmed with biopsy. They were effectively treated with excision of the ischiopubic ramus, aggressive curettage, drilling, and phenolization at the margins. The surgery was performed in a gynecological position with an approach over the ischiopubic ramus. Both cases present no recurrence (two and 10-year follow-up), and neither has a significant impact on the quality of life. A thorough plan and surgical technique were essential for the success of this intervention.

Genetic characterization of a novel organoid from human malignant giant-cell tumor

Malignant giant-cell tumors are extremely rare bone sarcomas that transform from conventional giant-cell tumors during long periods of treatment. Owing to their rarity, no further analysis of their molecular pathogenesis exists, and thus, no standard treatment has been established. Recently, organoid culture methods have been highlighted for recapturing the tumor microenvironment, and we have applied the culture methods and succeeded in establishing patient-derived organoids (PDO) of rare sarcomas. This study aimed to investigate the genomic characteristics of our established novel organoids from human malignant giant-cell tumors. At our institute, we treated a patient with malignant giant-cell tumor. The remaining sarcoma specimens after surgical resection were cultured according to the air-liquid interface organoid-culture method. Organoids were xenografted into NOD-scid IL2Rgnull mice. The developed tumors were histologically and genomically analyzed to compare their characteristics with those of the original tumors. Genetic changes over time throughout treatment were analyzed, and the genomic status of the established organoid was confirmed. Organoids from malignant giant-cell tumors could be serially maintained using air-liquid interface organoid-culture methods. The tumors developed in xenografted NOD-scid IL2Rgnull mice. After several repetitions of the process, a patient-derived organoid line from the malignant giant-cell tumor was established. Immunohistochemical analyses and next-generation sequencing revealed that the established organoids lacked the H3-3A G34W mutation. The xenografted organoids of the malignant giant-cell tumor had phenotypes histologically and genetically similar to those of the original tumor. The established organoids were confirmed to be derived from human malignant giant-cell tumors. In summary, the present study demonstrated a novel organoid model of a malignant giant-cell tumor that was genetically confirmed to be a malignant transformed tumor. Our organoid model could be used to elucidate the molecular pathogenesis of a malignant giant-cell tumor and develop novel treatment modalities.

Computed Tomography Bone Imaging: Pushing the Boundaries in Clinical Practice

Bone microarchitecture has several clinical implications over and above estimating bone strength. Computed tomography (CT) analysis mainly uses high-resolution peripheral quantitative CT and micro-CT, research imaging techniques, most often limited to peripheral skeleton assessment. Ultra-high-resolution (UHR) CT and photon-counting detector CT, two commercially available techniques, provide images that can approach the spatial resolution of the trabeculae, bringing bone microarchitecture analysis into clinical practice and improving depiction of bone vascularization, tumor matrix, and cortical and periosteal bone. This review presents bone microarchitecture anatomy, principles of analysis, reference measurements, and an update on the performance and potential clinical applications of these new CT techniques. We also share our clinical experience and technical considerations using an UHR-CT device.

Giant Cells of Various Lesions Are Characterised by Different Expression Patterns of HLA-Molecules and Molecules Involved in the Cell Cycle, Bone Metabolism, and Lineage Affiliation: An Immunohistochemical Study with a Review of the Literature

Giant cells (GCs) are thought to originate from the fusion of monocytic lineage cells and arise amid multiple backgrounds. To compare GCs of different origins, we immunohistochemically characterised the GCs of reactive and neoplastic lesions (n = 47). We studied the expression of 15 molecules including HLA class II molecules those relevant to the cell cycle, bone metabolism and lineage affiliation. HLA-DR was detectable in the GCs of sarcoidosis, sarcoid-like lesions, tuberculosis, and foreign body granuloma. Cyclin D1 was expressed by the GCs of neoplastic lesions as well as the GCs of bony callus, fibroid epulis, and brown tumours. While cyclin E was detected in the GCs of all lesions, p16 and p21 showed a heterogeneous expression pattern. RANK was expressed by the GCs of all lesions except sarcoid-like lesions and xanthogranuloma. All GCs were RANK-L-negative, and the GCs of all lesions were osteoprotegerin-positive. Osteonectin was limited to the GCs of chondroblastoma. Osteopontin and TRAP were detected in the GCs of all lesions except xanthogranuloma. RUNX2 was heterogeneously expressed in the reactive and neoplastic cohort. The GCs of all lesions except foreign body granuloma expressed CD68, and all GCs were CD163- and langerin-negative. This profiling points to a functional diversity of GCs despite their similar morphology.

Potential alternative drug treatment for bone giant cell tumor

Background: Bone giant cell tumor (BGCT) is one of the world's major disease types of locally aggressive bone tumors. In recent years, denosumab treatment has been introduced before curettage surgery. However, the current therapeutic was practical only sometimes, given the local recurrence effects after discontinuation of denosumab. Due to the complex nature of BGCT, this study aims to use bioinformatics to identify potential genes and drugs associated with BGCT. Methods: The genes that integrate BGCT and fracture healing were determined by text mining. The gene was obtained from the pubmed2ensembl website. We filtered out common genes for the function, and signal pathway enrichment analyses were implemented. The protein-protein interaction (PPI) networks and the hub genes were screened by MCODE built-in Cytoscape software. Lastly, the confirmed genes were queried in the Drug Gene Interaction Database to determine potential genes and drugs. Results: Our study finally identified 123 common specific genes in bone giant cell tumors and fracture healing text mining concepts. The GO enrichment analysis finally analyzed 115 characteristic genes in BP, CC, and MF. We selected 10 KEGG pathways and identified 68 characteristic genes. We performed protein-protein interaction analysis (PPI) on 68 selected genes and finally identified seven central genes. In this study, these seven genes were substituted into drug-gene interactions, and there were 15 antineoplastic drugs, 1 anti-involving drug, and 1 anti-influenza drug. Conclusion: The 7 genes (including ANGPT2, COL1A1, COL1A2, CTSK, FGFR1, NTRK2, and PDGFB) and 17 drugs, which have not been used in BGCT, but 6 of them approved by the FDA for other diseases, could be potential genes and drugs, respectively, to improve BGCT treatment. In addition, the correlation study and analysis of potential drugs through genes provide great opportunities to promote the repositioning of drugs and the study of pharmacology in the pharmaceutical industry.

Tumor Growth Rate in Spinal Giant Cell Tumors of Bone and Association With the Immune Microenvironment and Denosumab Treatment Responsiveness: A Multicenter Study

BACKGROUND

Currently, little is known about the prognostic value of tumor growth rate (TGR) in spinal giant cell tumors of bone (GCTB).

OBJECTIVE

To investigate the correlation of TGR with clinicopathological features, immune microenvironment, prognosis, and response to denosumab treatment of spinal GCTB.

METHODS

A total of 128 patients with spinal GCTB treated at 5 centers from 2011 to 2021 were included. TGR was assessed by 2 independent neuroradiologists using at least 2 preoperative thin-section magnetic resonance imaging scans at a minimum interval of 2 months. Immunohistochemistry was used to assess tumor-infiltrating lymphocyte subtypes for CD3, CD4, CD8, CD20, PD-1, PD-L1, and Foxp3. Then, these parameters were analyzed for their associations with patient outcomes (progression-free survival and overall survival), clinicopathological features, and denosumab treatment responsiveness.

RESULTS

High TGR predicted both poor progression-free survival and overall survival (both P < .001). In addition, TGR was associated with postoperative neurological dysfunction ( P < .001), Enneking staging ( P = .016), denosumab treatment responsiveness ( P = .035), and the number of CD3 + ( P < .001), PD-1 + ( P = .009), PD-L1 + ( P < .001), and FoxP3 + tumor-infiltrating lymphocyte ( P = .02). Importantly, TGR outperformed the traditional Enneking, Campanacci, and American Joint Committee on Cancer staging systems in predicting the clinical outcomes of spinal GCTB.

CONCLUSION

These data support the use of TGR as a reliable predictive tool for clinically relevant outcomes and response to denosumab therapy of spinal GCTB, which may be helpful in guiding prognostic risk stratification and therapeutic optimization of patients.

The optimal strategy for 3D-printed uncemented endoprosthesis for the bone defect reconstruction of the distal radius, based on biomechanical analysis and retrospective cohort study

INTRODUCTION

Prosthetic reconstruction after resecting giant cell tumor of bone (GCTB) of the distal radius has been proposed. However, this is generally associated with various complications. To improve the functional outcomes, we designed a three-dimensional (3D)-printed uncemented endoprosthesis. Meanwhile, using finite-element analysis and clinical observation, an optimization strategy was explored.

MATERIALS AND METHODS

We retrospectively analyzed patients with Campanacci III or recurrent GCTB of the distal radius who underwent 3D-printed uncemented endoprosthesis reconstruction. Clinically, according to the different palmar tilts of the endoprosthesis, patients were divided into the biological angle (BA) group and the zero-degree (ZD) group. We recorded and evaluated the differences in functional outcomes and complications between the two groups. Biomechanically, four 3D finite-element models (normal and customized endoprostheses with three different implemented palmar tilts) were developed.

RESULTS

We analyzed 22 patients (12 males and 10 females). The median follow-up period was 60 (range, 19-82) months. Of the 22 patients, 11 patients were included in the BA group and the remaining 11 patients were in the ZD group. Both groups showed no significant differences in the range of motion, Mayo score, and disabilities of the arm, shoulder, and hand scores postoperatively. The subluxation rate was significantly lower in the ZD group than in the BA group. The biomechanical results showed similar stress and displacement distribution patterns in the normal and prosthetic reconstruction models. Additionally, the endoprosthesis with 0° palmar tilt showed better biomechanical performance.

CONCLUSION

3D-printed uncemented endoprosthesis provides acceptable midterm outcomes in patients undergoing distal radius reconstruction. Optimizing the design by decreasing the palmar tilt may be beneficial for decreasing the risk of wrist joint subluxation.

Progress on Denosumab Use in Giant Cell Tumor of Bone: Dose and Duration of Therapy

Giant cell tumor of bone (GCTB) is an aggressive non-cancerous bone tumor associated with risks of sarcoma and metastasis. Once malignancy occurs, the prognosis is generally poor. Surgery remains the main treatment for GCTB. Multidisciplinary management is a feasible option for patients wherein surgical resection is not an option or for those with serious surgery-related complications. Denosumab is an anti-nuclear factor kappa B ligand approved for the treatment of postmenopausal women with osteoporosis, bone metastases, and advanced or inoperable GCTB. However, the guidelines for treating GCTB are unclear; its short-term efficacy and safety in inoperable patients have been demonstrated. Lengthier therapies (high cumulative doses) or pre-operative adjuvant therapy may be associated with severe complications and high local recurrence rates. Short-term administration helps attain satisfactory local control and functionality. As a result, lately, the impact of different doses and lengths of treatment on the efficacy of denosumab in GCTB treatment, the incidence of complications, and recurrence rates have gained attention. The efficacy and safety of denosumab against GCTB, its impact on imaging assessment, related complications, and recurrence of GCTB were previously reviewed. For further research direction, this paper reviews the progress of studies evaluating the impact of the dose and duration of denosumab therapy for GCTB.

Network Pharmacology and Molecular Docking Analysis on Molecular Targets and Mechanisms of Bushen Hugu Decoction in the Treatment of Malignant Tumor Bone Metastases

Purpose. To explore the active compounds of the Chinese medicine prescriptions of Bushen Hugu Decoction (BHD) and demonstrate its mechanisms against malignant tumor bone metastasis (BM) through network pharmacology and molecular docking analysis.Methods. The main components and targets of BHD were retrieved from the TCMSP database, and the targets were normalized by UniProt. The Herbs-Components-Targets network of BHD was established by Cytoscape. The main BM targets were obtained from GeneCards, TTD, DrugBank, and OMIM. STRING and Cytoscape were used to construct a PPI network and obtain hub genes. DAVID and Metascape were used for GO and KEGG enrichment analyses. According to the network topology parameters, the top 4 components were selected for molecular docking verification with the core targets. Results. Compound–target network of BHD mainly contained 51 compounds and 259 corresponding targets including 107 BHD-BM targets. PPI interaction network and subnetworks identified ten hub genes. GO enrichment analysis found 1970 terms ( $p<0.05$ ), and 164 signaling pathways ( $p<0.05$ ) were found in KEGG, including PI3K-Akt signaling pathway, proteoglycans in cancer, prostate cancer, MAPK signaling pathway, and IL-17 signaling pathway. Molecular docking analysis showed that the active components of BHD, quercetin, luteolin, kaempferol, and aureusidin have good binding activity to the core targets. Conclusion. The potential molecular target and signaling pathways were found for BHD major active components. It provides guidance for the future mechanism research of the BHD in malignant tumor bone metastasis. This study also established the foundation for the new strategy for the pharmacology study of Chinese medicine.

A bibliometric research based on hotspots and frontier trends of denosumab

Denosumab is a monoclonal antibody that targets and inhibits the osteoclast activating factor receptor activator for nuclear factor-κB ligand (RANKL). It has been widely used in the treatment of osteoporosis, giant cell tumors of bone, and in the prevention of malignant skeletal-related events (SREs). We collected the research results and related MeSH terms of denosumab from 2011 to 2021 through the Web of Science and PubMed, respectively. The literature was visualized and analyzed by CiteSpace and bibliometric online analysis platforms. The MeSH terms were biclustered using the Bibliographic Co-Occurrence Analysis System (BICOMB) and graph clustering toolkit (gCLUTO). The results show that the number of denosumab-related annual publications had increased from 51 to 215, with the United States leading and Amgen Inc. being the most influential in the past 10 years. Articles published in the Journal of Bone and Mineral Research had the highest total citations. Three scholars from Shinshu University in Matsumoto, Yukio Nakamura, Takako Suzuki, and Hiroyuki Kato, joined the field relatively late but produced the most. The clinical comparison and combination of denosumab with other drugs in the treatment of osteoporosis was the most significant focus of research. Drug withdrawal rebound and management strategies have gained more attention and controversy recently. MeSH analysis revealed eight major categories of research hotspots. Among them, exploring the multiple roles of the RANK-RANKL-OPG system in tumor progression, metastasis, and other diseases is the potential direction of future mechanism research. It is a valuable surgical topic to optimize the perioperative drug administration strategy for internal spinal fixation and orthopedic prosthesis implantation. Taken together, the advantages of denosumab were broad and cost-effective. However, there were still problems such as osteonecrosis of the jaw, severe hypocalcemia, a high recurrence rate of giant cells in the treatment of bone and individual sarcoidosis, and atypical femoral fractures, which need to be adequately solved.

Malignant Transformation of Giant Cell Tumour of Bone: A Review of Literature and the Experience of a Referral Centre

Giant cell tumour of bone (GCTB) is a benign, locally aggressive primary bone neoplasm that represents 5% of all bone tumours. The principal treatment approach is surgery. Although generally GCTB is considered only a locally aggressive disease, it can metastasise, and lung metastases occur in 1–9% of patients. To date, only the use of denosumab has been approved as medical treatment for GCTB. Even more rarely, GCTB undergoes sarcomatous transformation into a malignant tumour (4% of all GCTB), but history of this malignant transformation is unclear and unpredictable. Considering the rarity of the event, the data in the literature are few. In this review, we summarise published data of GCTB malignant transformation and we analyse three cases of malignant transformation of GCTB, evaluating histopathology, genetics, and radiological aspects. Despite the rarity of this event, we conclude that a strict follow up is recommended to detect early malignant transformation.

Comprehensive treatment outcomes of giant cell tumor of the spine: A retrospective study

There is no consensus on a treatment strategy for spinal giant cell tumor of bone (GCTB) because of the difficulty in their treatment. Treatment options often include the use of the controversial denosumab, an antibody therapy aimed at tumor shrinkage, different curettage techniques, resection, or a combination of these therapies. The current study aimed to identify treatment methods associated with favorable outcomes in patients with spinal GCTB. We retrospectively reviewed 5 patients with spinal GCTB, including patients with tumors of the sacrum, treated at our hospital between September 2011 and November 2020. Two men and 3 women were included in the study. The median follow-up period was 74 months (range: 14-108 months). We surveyed the tumor site, treatment method, denosumab use, and outcomes. The median age was 17 years (range: 17-42 years). There were 2 cases of sacral GCTB and 1 case each of lumbar, cervical, and thoracic vertebral GCTB. The comorbidities observed included hepatitis, malignant lymphoma, atopic dermatitis, and asthma. The treatment method included zoledronic acid after embolization and denosumab, denosumab only, curettage and posterior fusion, and curettage resection after embolization and anterior and posterior fusion. Denosumab was used in all cases. Three patients were continuously disease-free, 1 patient with no evidence of disease, and 1 patient alive with disease. Aggressive treatment, especially surgical treatment, may lead to good results in spinal GCTB.

Clinicopathological and histological analysis of secondary malignant giant cell tumors of bone without radiotherapy

Giant cell tumor of bone (GCTB) is an intermediate bone tumor that rarely undergoes malignant transformation. Secondary malignant GCTB (SMGCTB) is defined as a lesion in which high-grade sarcoma occurs at the site of previously treated GCTB. The present study retrospectively reviewed the medical records of patients with GCTB treated at Okayama University Hospital between April 1986 and April 2020. The clinicopathological and histological features of patients with SMGCTB without prior radiotherapy were investigated. A total of three patients (4%) with SMGCTB were detected, and the tumor sites were the distal ulna, distal femur and sacrum. Two of the patients had been treated with curettage and bone graft, and one had been treated with denosumab. In all cases, the lesions were made up of two components, the conventional GCTB component and the malignant component. The Ki67 labeling index was higher in the malignant components of SMGCTB and metastatic lesions compared with that in primary and recurrent conventional GCTB, or the conventional GCTB component of SMGCTB. Moreover, p53 expression was higher in these same components in patients who underwent curettage and bone grafting; however, there was no difference in the patient that received denosumab treatment. In this patient, clinical cancer genomic profiling revealed loss of CDKN2A, CDKN2B and MTAP expression. All three patients developed distant metastasis. The patients with SMGCTB in the ulna and femur died 13 and 54 months after detection of malignant transformation, respectively. The patient with SMGCTB in the sacrum received carbon-ion radiotherapy to the sacrum and pazopanib; the treatment was effective and the patient was alive at the last follow-up 3 years later. In conclusion, p53 may be associated with malignant transformation in GCTB. Future studies should investigate the association of between denosumab treatment and malignant transformation, as well as molecular targeted therapy to improve the clinical outcomes of SMGCTB.

Rechallenge of denosumab in advanced giant cell tumor of the bone after atypical femur fracture: A case report and review of literature

Giant cell tumor of the bone (GCTB) is a locally aggressive neoplasm where surgery is often curative. However, it can rarely give rise to distant metastases. Currently, the only available active therapeutic option for unresectable GCTB is denosumab, an anti-RANKL monoclonal antibody that dampens the aggressive osteolysis typically seen in this disease. For advanced/metastatic GCTB, denosumab should be continued lifelong, and although it is usually well tolerated, important questions may arise about the long-term safety of this drug. In fact, uncommon but severe toxicities can occur and eventually lead to denosumab discontinuation, such as atypical fracture of the femur (AFF). The optimal management of treatment-related AFF is a matter of debate, and to date, it is unknown whether reintroduction of denosumab at disease progression is a clinically feasible option, as no reports have been provided so far. Hereinafter, we present a case of a patient with metastatic GCTB who suffered from AFF after several years of denosumab; we describe the clinical features, orthopedic treatment, and oncological outcomes, finally providing the first evidence that denosumab rechallenge after AFF occurrence may be a safe and viable option at GCTB progression.

The Roles of TNF Signaling Pathways in Metabolism of Bone Tumors

The metabolism of bone tumors is extraordinarily complex and involves many signaling pathways and processes, including the tumor necrosis factor (TNF) signaling pathway, which consists of TNF factors and the TNF receptors that belong to the TNF receptor superfamily (TNFRSF). It is appreciated that signaling events and pathways involving TNFRSF components are essential in coordinating the functions of multiple cell types that act as a host defense network against pathogens and malignant cells, the implications of TNFRSF-related signaling pathways on bone tumor metabolism remain to be summarized, which is one of the significant obstacles to the application of TNF-related treatment modalities in the domain of bone oncology. This review will discuss and summarize the anti-tumor properties of important TNFRSF components concerning osteosarcoma, chondrosarcoma, and Ewing sarcoma.

Secondary Malignancy in Giant Cell Tumor: A Single-Center Study

Giant cell tumor of bone (GCTB) undergoes a sarcomatous transformation. Secondary malignancy in giant cell tumor (MGCT) is associated with radiotherapy and has a dismal prognosis. We reviewed medical records to investigate the clinicopathological characteristics and prognosis of MGCT patients. The enrollment criterion was high-grade spindle-cell sarcoma, which developed at the site of prior GCTB treatment. Twelve patients were analyzed: six females and six males. The median age was 42.5 years. Benign recurrence occurred in five GCTB patients not treated with radiotherapy. No pulmonary implants were observed. The median latency to the malignant transformation was 63 months. Nine patients were AJCC stage IIB, and three were stage IVA. The median follow-up period after malignant transformation was 62.5 months. Five patients developed local recurrence, and six had distant metastasis. Five-year overall recurrence and metastasis-free survival rates were 61.9%, 66.7%, and 58.3%, respectively. Initial metastasis was a predictive factor for overall survival. Benign local recurrence of GCTB was also a negative factor for metastasis-free survival of MGCT patients. Differences in overall survival according to benign recurrence also showed a tendency toward significance. In our series, secondary MGCT did not occur after radiotherapy. The prognosis was better than previous findings. Benign recurrence of GCTB could reflect the prognosis of MGCT.

Denosumab Versus Zoledronic Acid in Cases of Surgically Unsalvageable Giant Cell Tumor of Bone: A Randomized Clinical Trial

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Denosumab and zoledronic acid had similar tumor responses and clinical benefits.

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Disease progression was observed in patients in the DB group (12.5%) than ZA group (15.0%).

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Denosumab treatment was markedly more expensive than zoledronic acid treatment (p < 0.0001).

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The recurrence-free survival rate at 4-year follow-up is higher in DB group (p = 0.035).

Background

Giant-cell tumor of bone (GCTB) is a relatively benign, but locally aggressive osteoclastogenic stromal tumour of the bone. Although denosumab has been approved as an monoclonal antibody against RANK ligand for the treatment of GCTB, few clinical trials of the benefit in tumor response have been conducted to prove the efficiency in Chinese population.

Objectives

In this multicentric, random controlled, clinical trial, 160 patients were enrolled to compare the therapeutic efficacy and safety of denosumab and zoledronic acid treatment in patients with surgically unsalvageable GCTB.

Methods

Between 2nd Jan 2015 and 1st Jan 2018, 160 adults (aged ≥ 18 years) with ①surgically unsalvageable GCTB, ②surgically salvageable GCTB with planned surgery expected to result in severe morbidity were included in this randomized clinical trial. Patients received either subcutaneous denosumab (DB group; 120 mg once every 4 weeks with loading doses of 120 mg subcutaneously admininstered on days 8 and 15; n = 80) or intravenous zoledronic acid (ZA group; 4 mg once every 4 weeks; n = 80) for six cycles. Disease status, clinical benefits, treatment-emergent adverse effects, overall survival, and cost of treatment were evaluated during the follow-up period. Statistical significance was determined using 95% confidence intervals.

Results

Denosumab and zoledronic acid had similar tumor responses (p = 0.118) and clinical benefits (p = 0.574). Disease progression was observed in fewer patients in the DB group (12.5%) than ZA group (15.0%). Denosumab caused fatigue (p = 0.001) and back pain (p < 0.0001), while zoledronic acid caused hypocalcemia (p < 0.0001), flu-like symptoms (p = 0.059) and hypotension (p = 0.059). Denosumab treatment was markedly more expensive than zoledronic acid treatment (p < 0.0001). The cost to manage treatment-emergent adverse effects was the same for the ZA group and the DB group (p = 0.425). The accumulate recurrence-free survival rate at 4-year follow-up is higher in DB group (p = 0.035).

Conclusions

Denosumab is a safe but costly alternative to zoledronic acid for treatment of surgically unsalvageable GCTB.

Denosumab in Giant Cell Tumor of Bone: Multidisciplinary Medical Management Based on Pathophysiological Mechanisms and Real-World Evidence

Simple Summary

The widely accepted local therapy in extremity giant cell tumor of bone (GCTB) is surgery, in the form of extended intralesional curettage with adequate disease clearance and retention of the limb, wherever possible. Denosumab is a relevant therapy option for advanced GCTB, to benefit tumor response and surgical down-staging. Most GCTB patients with localized disease can be successfully treated with surgical curettage; patients with primary unresectable lesions or metastases may experience long-term clinical and radiological remission and pain control with denosumab treatment, and in this clinical situation, denosumab is currently the treatment of choice.

Abstract

(1) Despite the benign nature of the giant cell tumor of bone (GCTB), it shows a local recurrence rate of up to 50% and a chance of malignant transformation. The widely accepted local therapy in extremity GCTB is surgery, in the form of extended intralesional curettage with adequate disease clearance and retention of the limb, wherever possible. Denosumab, a human monoclonal antibody directed against the RANKL and associated inhibition of the RANKL pathway, is a relevant therapy option for advanced GCTB, to benefit tumor response and surgical down-staging. (2) The literature review of patients with GCTB treated with denosumab is performed via PubMed, using suitable keywords from January 2009 to January 2021. (3) Current indications for denosumab use are not definitively clear and unambiguous. Most GCTB patients with localized disease can be successfully treated with surgical curettage, and the role of denosumab in preoperative therapy in this patient population remains unclear. (4) However, patients with primary unresectable lesions or metastases may experience long-term clinical and radiological remission and pain control with denosumab treatment, and in this clinical situation, denosumab is currently the treatment of choice.

Improved Characteristics of RANKL Immuno-PET Imaging Using Radiolabeled Antibody Fab Fragments

Purpose: RANKL expression in the tumor microenvironment has been identified as a biomarker of immune suppression, negating the effect of some cancer immunotherapies. Previously we had developed a radiotracer based on the FDA-approved RANKL-specific antibody denosumab, [⁸⁹Zr]Zr-DFO-denosumab, enabling successful immuno-PET imaging. Radiolabeled denosumab, however, showed long blood circulation and delayed tumor uptake, potentially limiting its applications. Here we aimed to develop a smaller radiolabeled denosumab fragment, [⁶⁴Cu]Cu-NOTA-denos-Fab, that would ideally show faster tumor accumulation and better diffusion into the tumor for the visualization of RANKL. Experimental design: Fab fragments were prepared from denosumab using papain and conjugated to a NOTA chelator for radiolabeling with ⁶⁴Cu. The bioconjugates were characterized in vitro using SDS-PAGE analysis, and the binding affinity was assessed using a radiotracer cell binding assay. Small animal PET imaging evaluated tumor targeting and biodistribution in transduced RANKL-ME-180 xenografts. Results: The radiolabeling yield of [⁶⁴Cu]Cu-NOTA-denos-Fab was 58 ± 9.2%, with a specific activity of 0.79 ± 0.11 MBq/µg (n = 3). A radiotracer binding assay proved specific targeting of RANKL in vitro. PET imaging showed fast blood clearance and high tumor accumulation as early as 1 h p.i. (2.14 ± 0.21% ID/mL), which peaked at 5 h p.i. (2.72 ± 0.61% ID/mL). In contrast, [⁶⁴Cu]Cu-NOTA-denosumab reached its highest tumor uptake at 24 h p.i. (6.88 ± 1.12% ID/mL). [⁶⁴Cu]Cu-NOTA-denos-Fab specifically targeted human RANKL in transduced ME-180 xenografts compared with the blocking group and negative ME-180 xenograft model. Histological analysis confirmed RANKL expression in RANKL-ME-180 xenografts. Conclusions: Here, we report on a novel RANKL PET imaging agent, [⁶⁴Cu]Cu-NOTA-denos-Fab, that allows for fast tumor imaging with improved imaging contrast when compared with its antibody counterpart, showing promise as a potential PET RANKL imaging tool for future clinical applications.

Giant Cell Tumor of Bone Versus Tenosynovial Giant Cell Tumor - Similarities and Differences

Giant cell tumor of bone (GCTB) and tenosynovial giant cell tumor (TGCT) share misleadingly similar names, soft texture and brown color macroscopically, osteoclast-like multinucleated giant cells microscopically and localisation in the musculoskeletal system. However, these two tumor types are biologically and clinically two distinct entities with different natural courses of progression and considerably different modes of surgical and medical treatment. In this article, we provide a detailed update on the similarities and the differences between both tumor types.GCTB is a locally aggressive osteolytic bone tumor, commonly seen in patients in their third decade of life. It usually occurs as a solitary lesion in the meta-epiphyseal region of long bones. It can be diagnosed using plain radiographic imaging, CT radiography or MRI to estimate the tumor extent, soft tissue and joint involvement. GCTB is usually treated with intralesional excision by curettage. Systemically, it can be treated with bisphosphonates and denosumab or radiotherapy.TGCT is a rare, slowly progressing tumor of synovial tissue, affecting the joint, tendon sheath or bursa, mostly seen in middle-aged patients. TGCT is usually not visible on radiographs and MRI is mostly used to enable assessment of potential bone involvement and distinguishing between two TGCT types. Localised TGCT is mostly treated with marginal surgical resection, while diffuse TGCT is optimally treated with total synovectomy and is more difficult to remove. Additionally, radiotherapy, intraarticular injection of radioactive isotopes, anti-TNF-α antibodies and targeted medications may be used.

State of the Art and New Concepts in Giant Cell Tumor of Bone: Imaging Features and Tumor Characteristics

Simple Summary

The 2020 World Health Organization classification of soft tissue and bone tumors classified the giant cell tumor of bone (GCTB) as an intermediate malignant tumor, with locally aggressive behavior and high recurrence rate. Imaging plays a pivotal role in the assessment of GCTB, and this review tries to summarize the main concepts about GCTB histopathogenesis and new biomarkers, describing those GCTB imaging findings which could possibly be explained by tumor molecular alterations. We have illustrated pre-operative imaging features related to prognosis and radiological findings for response evaluation after surgical treatment and denosumab administration. We have also reported the results described in literature regarding the role of radiomics in aiding GCTB diagnosis, predicting possible post-treatment recurrence and providing a quantitative assessment of the response to denosumab treatment.

Abstract

Giant cell tumor of bone (GCTB) is classified as an intermediate malignant tumor due to its locally aggressive behavior, burdened by high local recurrence rate. GCTB accounts for about 4–5% of all primary bone tumors and typically arises in the metaphysis and epiphyses of the long tubular bones. Mutation of gene H3F3A is at the basis of GCTB etiopathogenesis, and its immunohistochemical expression is a valuable method for practical diagnosis, even if new biomarkers have been identified for early diagnosis and for potential tumor recurrence prediction. In the era of computer-aided diagnosis, imaging plays a key role in the assessment of GCTB for surgical planning, patients’ prognosis prediction and post treatment evaluation. Cystic changes, penetrating irregular margins and adjacent soft tissue invasion on preoperative Magnetic Resonance Imaging (MRI) have been associated with a higher rate of local recurrence. Distance from the tumor edge to the articular surface and thickness of unaffected cortical bone around the tumor should be evaluated on Computed Tomography (CT) as related to local recurrence. Main features associated with local recurrence after curettage are bone resorption around the graft or cement, soft tissue mass formation and expansile destruction of bone. A denosumab positive response is represented by a peripherical well-defined osteosclerosis around the lesion and intralesional ossification. Radiomics has proved to offer a valuable contribution in aiding GCTB pre-operative diagnosis through clinical-radiomics models based on CT scans and multiparametric MR imaging, possibly guiding the choice of a patient-tailored treatment. Moreover, radiomics models based on texture analysis demonstrated to be a promising alternative solution for the assessment of GCTB response to denosumab both on conventional radiography and CT since the quantitative variation of some radiomics features after therapy has been correlated with tumor response, suggesting they might facilitate disease monitoring during post-denosumab surveillance.

Recurrent giant cell tumour of the distal ulna after en bloc resection with preoperative denosumab use

In recent years, denosumab has been used to treat giant cell tumour of bone (GCTB) not only in cases where surgery is complicated but also preoperatively to decrease the preoperative grade or to facilitate surgery for Campanacci grade II and III cases. However, there are no clear protocols regarding the preoperative use of denosumab before en bloc resection. There are a few reports of recurrent cases after en bloc resection; however, the association with the use of denosumab is unknown. We present the clinical, radiological and histopathological findings of a case of Campanacci grade III GCTB at the distal end of the ulna, which resulted in soft tissue recurrence after en bloc resection with the preoperative use of denosumab.

Single-Cell RNA Sequencing Reveals the Migration of Osteoclasts in Giant Cell Tumor of Bone

Giant cell tumor of bone (GCTB) is benign tumor that can cause significant osteolysis and bone destruction at the epiphysis of long bones. Osteoclasts are thought to be highly associated with osteolysis in GCTB. However, the migration of osteoclasts in GCTB remains unclear. A deeper understanding of the complex tumor microenvironment is required in order to delineate the migration of osteoclasts in GCTB. In this study, samples were isolated from one patient diagnosed with GCTB. Single-cell RNA sequencing (scRNA-seq) was used to detect the heterogeneity of GCTB. Multiplex immunofluorescence staining was used to evaluate the cell subtypes identified by scRNA-seq. A total of 8,033 cells were obtained from one patient diagnosed with GCTB, which were divided into eight major cell types as depicted by a single-cell transcriptional map. The osteoclasts were divided into three subsets, and their differentiation trajectory and migration status were further analyzed. Osteoclast migration may be regulated via a series of genes associated with cell migration. Furthermore, four signaling pathways (RANKL, PARs, CD137 and SMEA3 signaling pathway) were found to be highly associated with osteoclast migration. This comprehensive single-cell transcriptome analysis of GCTB identified a series of genes associated with cell migration as well as four major signaling pathways that were highly related to the migration of osteoclasts in GCTB. Our findings broaden the understanding of GCTB bionetworks and provides a theoretical basis for anti-osteolysis therapy against GCTB in the future.

Denosumab in the management of Aneurysmal bone cyst

BACKGROUND

Aneurysmal bone cyst (ABC) is a benign, locally aggressive tumour that arises predominantly in long bones and spine. Following the encouraging results of denosumab use in Giant Cell Tumors (GCT) and the histological similarities between ABC and GCT, the interest on the role of denosumab in the therapeutic arsenal of the most advanced ABC is growing. The purpose of this literature review is to investigate the current state of knowledge about the use of denosumab in ABCs.

METHODS

A literature research was conducted through PUBMED, COCHRANE and GOOGLE SCHOLAR using the keywords "aneurysmal bone cyst" AND "denosumab". Seventeen articles were included.

RESULTS

A total of 43 cases were reported in the literature. There were 23 males, 20 females. The mean age was 15,9±8,1 year. Pain relief and neurological improvement were rapid and sustained. Radiological assessment showed ossification and/or volume reduction in 36/39 patients. Eight patients (18,6%) presented a recurrence after or during denosumab therapy of whom 7 were adults. Adverse events occurred in 11 patients, 5 of them were admitted to the intensive care unit due to hypercalcemia.

CONCLUSION

Denosumab use in non-surgical ABCs has shown a positive impact in pain and neurological symptoms. The oncological outcome remains unclear with a recurrence rate of 18,6% during/after denosumab therapy, mostly in adults. However, regarding the potential clinical benefits, its use might be discussed in the most advanced cases. Further research and clinical trials are mandatory to precise its belonging in the therapeutic arsenal.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Immuno-PET Molecular Imaging of RANKL in Cancer

PURPOSE

The involvement of RANK/RANKL signaling in the tumor microenvironment (TME) in driving response or resistance to immunotherapy has only very recently been recognized. Current quantification methods of RANKL expression suffer from issues such as sensitivity, variability, and uncertainty on the spatial heterogeneity within the TME, resulting in conflicting reports on its reliability and limited use in clinical practice. Non-invasive molecular imaging using immuno-PET is a promising approach combining superior targeting specificity of monoclonal antibodies (mAb) and spatial, temporal and functional information of PET. Here, we evaluated radiolabeled anti-RANKL mAbs as a non-invasive biomarker of RANKL expression in the TME.

EXPERIMENTAL DESIGN

Anti-human RANKL mAbs (AMG161 and AMG162) were radiolabeled with ⁸⁹Zr using the bifunctional chelator DFO in high yield, purity and with intact binding affinity. After assessing the biodistribution in healthy CD-1 nude mice, [⁸⁹Zr]Zr-DFO-AMG162 was selected for further evaluation in ME-180 (RANKL-transduced), UM-SCC-22B (RANKL-positive) and HCT-116 (RANKL-negative) human cancer xenografts to assess the feasibility of in vivo immuno-PET imaging of RANKL.

RESULTS

[⁸⁹Zr]Zr-DFO-AMG162 was selected as the most promising tracer for further validation based on biodistribution experiments. We demonstrated specific accumulation of [⁸⁹Zr]Zr-DFO-AMG162 in RANKL transduced ME-180 xenografts. In UM-SCC-22B xenograft models expressing physiological RANKL levels, [⁸⁹Zr]Zr-DFO-AMG162 imaging detected significantly higher signal compared to control [⁸⁹Zr]Zr-DFO-IgG2 and to RANKL negative HCT-116 xenografts. There was good visual agreement with tumor autoradiography and immunohistochemistry on adjacent slides, confirming these findings.

CONCLUSIONS

[⁸⁹Zr]Zr-DFO-AMG162 can detect heterogeneous RANKL expression in the TME of human cancer xenografts, supporting further translation of RANKL immuno-PET to evaluate tumor RANKL distribution in patients.