Multimodal management of tenosynovial giant cell tumors (TGCT) in the landscape of new druggable targets.

Tenosynovial giant cell tumor (TGCT) is a rare, benign, locally aggressive synovial based neoplastic process that can result in functional debilitation and end-stage arthrtitis. Although surgical resection is the primary treatment modality, novel systemic therapies are emerging as part of the multimodal armamentarium for patients with unresectable or complex disease burden. This review discusses the pathogenesis of TGCT, potential druggable targets and therapeutic approaches. It also evaluates the safety and efficacy of different systemic therapies.

Tenosynovial giant cell tumor.

Tenosynovial Giant Cell Tumor (TGCT) is a group of typically benign lesions arising from the synovium of joints, bursae and tendon sheaths. Depending on their growth pattern and clinical course, they are divided into localized and diffuse types. It is predominantly caused by a mutation in the stromal cells of the synovial membrane leading to overexpression of the colony stimulating factor 1 that recruits CSF1R-expressing cells of the mononuclear phagocyte lineage into the tumor mass. The lesions contain mainly histiocyte-like and synovial cells accompanied by varying numbers of multinucleated giant cells, mononuclear cells, foam cells, inflammatory cells and hemosiderin deposits. The gold standard for detect- ing and monitoring the disease is MRI, where the characteristic hemosiderin accumulation can be best appreciated, but it is a histological examination that is most conclusive. The main treatment is surgical resection of all pathological tissue, but radio- and chemotherapy are also viable options for certain groups of patients.

The efficacy of cannabidiol on renal angiomyolipoma and subependymal giant cell tumor volume in tuberous sclerosis complex.

In patients with tuberous sclerosis complex (TSC) the upregulation of the mechanistic target of rapamycin (mTOR) pathway leads to the development and growth of subependymal giant cell tumors (SGCTs) and renal angiomyolipomas (AMLs). Drugs that inhibit the mTOR pathway, such as sirolimus, can reduce the size of both SGCTs and AMLs. Recent preclinical studies have suggested cannabidiol (CBD) may mediate the mTOR pathway, however, its exact effects are unclear. This study examines the volumes of SGCTs and renal AMLs in patients with TSC during treatment with purified CBD for refractory epilepsy. We retrospectively reviewed the medical records of patients with TSC with radiological evidence of AMLs and SGCTs who were being treated with plant-derived highly purified CBD in oral solution (Epidiolex®, GW Research Ltd) for refractory epilepsy at Massachusetts General Hospital. Patients who had surgical intervention for AMLs or SGCTS, and patients who had been treated with mTOR inhibitors were excluded. The volumes of SGCTs and dominant renal AML were measured before and after CBD initiation using abdominal and brain scans and compared. Patient demographics and CBD doses were collected from medical records. Six out of the seven dominant renal AMLs and three out of the three SGCTs increased in volume during CBD treatment. One AML had a decrease in volume after CBD initiation which was not considered significant. The results suggest that unlike mTOR inhibitors, CBD treatment does not decrease the volume of SGCTs or AMLs in TSC patients.

A nonrandomized controlled study of sacral giant cell tumors with preoperative treatment of denosumab.

The aim of this nonrandomized controlled study (level 3)was to evaluate whether preoperative denosumab treatment can reduce intraoperative blood loss, facilitate surgical treatment, and improve local control of sacral giant-cell tumor (GCT).Surgical treatment of sacral GCT is very difficult due to extensive bone destruction and complex anatomical structures. The huge intraoperative blood loss may interrupt surgical management and judgment of tumor range. Denosumab can inhibit the differentiation of osteoclast-like giant cells and bone destruction by blocking RANKL-RANK pathway.Study group (preoperative denosumab treatment) and control group (no denosumab treatment) were matched for age, gender, tumor site, staging, and tumor size. In study group, enhanced computed tomography (CT) was performed before and after denosumab treatment. The comparison parameters between 2 groups: CT enhancement rate, intraoperative blood loss, and oncologic outcome.The mean preoperative time of denosumab treatment was 5.2 months in study group. The mean CT enhancement rate of study group was 2.60 before treatment and 1.37 after treatment (P = .012). The posttreatment CT enhancement rate of study group was significantly lower than that of control group (P = .007). The mean intraoperative bleeding of study group and control group was 2166.7 and 5240 mL, respectively (P = .040). The mean operative time of study group and control group was 268.3 and 268.5 minutes, respectively (P = .997). The recurrence rate of study group (66.7%) was significantly higher than that of control group (0%) (P = .046).Preoperative denosumab treatment has the tendency to reduce blood supply and intraoperative bleeding of sacral GCT. But the sclerosis and bony separation can increase the difficulty of tumor curettage and lead to high recurrence rate after denosumab treatment. It is necessary to study the best surgical opportunity after denosumab treatment and precise method to judge tumor range.

PD-1 axis expression in musculoskeletal tumors and antitumor effect of nivolumab in osteosarcoma model of humanized mouse.

BACKGROUND: Immune checkpoint inhibitors have led to a breakthrough in solid tumor immunotherapy, but related studies on musculoskeletal tumors are few, especially for PD-L2. METHODS: We examined expression of three molecular effectors of the PD-1 axis in 234 patients with musculoskeletal tumors, including osteosarcoma, chondrosarcoma, synovial sarcoma, and giant cell tumor. Survival analyses and potential mechanisms were investigated in osteosarcoma per the Gene Expression Omnibus (GEO) and immunohistochemistry analyses. In vivo, humanized mice were used to evaluate the effect of nivolumab on osteosarcoma. RESULTS: PD-L1, PD-L2, and PD-1 expression levels were significantly different between the histologic types of the musculoskeletal tumors. For osteosarcoma, PD-L1 was negatively correlated with prognosis, while PD-1 had a negative correlation tendency with overall survival (OS). Meanwhile, PD-L2 had a positive correlation trend with OS. Nivolumab inhibited osteosarcoma metastasis in humanized mice by increasing CD4+ and CD8+ lymphocytes and the cytolytic activity of CD8 lymphocytes in the lung but did not affect primary osteosarcoma growth. CONCLUSION: We systematically detected the expression patterns of PD-L1, PD-L2, and PD-1 in musculoskeletal tumors for the first time and demonstrated the prognostic roles and underlying mechanisms of PD-1 axis in osteosarcoma. Furthermore, PD-1 blockade could effectively control osteosarcoma pulmonary metastasis in vivo. Therefore, the PD-1 axis may be a potential immunotherapeutic target for metastatic osteosarcoma.

Combining of serial embolization and denosumab for large sacropelvic giant cell tumor: Case report of 3 cases.

RATIONALE: Both serial arterial embolization (SAE) and denosumab have been proved to be effective in treatment for giant cell tumor (GCT). There is potential synergic effect of combining two methods. The purpose of current study is to justify a new treatment strategy of combination of SAE and denosumab as neoadjuvant or stand-alone treatment for large sacropelvic giant cell tumor. PATIENT CONCERNS: Pelvic and sacral GCTs tend to be very large size and vascular. The concerns of surgical treatment were invasiveness of extensive surgery, intraoperative hemorrhage, nerve function jeopardized and local recurrence. However, SAE alone may not be adequate for complete removal of the tumor. DIAGNOSES: All the three cases were proved to be GCT by core-needle biopsy. Post-treatment pathological change was confirmed by further biopsy. INTERVENTIONS: The patient in Case 1 diagnosed of large recurrent sacral GCT received 6 times of endovascular embolizations with 2-month interval and started on denosumab simultaneously after first session of embolization. The second case was a 22-year-old female presented with a massive iliosacral tumor. SAE was performed for 3 sessions and the denosumab was started simultaneously. The patients was on treatment for half year. Both patients experienced a dramatic decrease in symptoms and concomitant improvement in function after the first embolization and weekly injection of denosumab. Tumor removal was performed on patient in case 2. The last case was a pelvic GCT and the patient received SAE and denosumab for half year. The tumor was then removed with purpose of complete cure. OUTCOMES: The first patient was still on denosumab with stable tumor. The other two patients were both free of recurrence after surgical removal of the tumors. No denosumab was used postoperatively. LESSONS: We reported the first three cases treated by combination of SAE and denosumab in the literature and aim to raise an alternative method for large GCT at challenging anatomical locations, for which surgery would carry significant risk. SAE and denosumab can synergically promote sclerosis and result in significant decrease in pain. It is reasonable to consider using SAE combined with denosumab neoadjuvantly to reduce the extensiveness and morbidity of surgery, however further investigation is warranted.

3-Dimensional micropillar drug screening identifies FGFR2-IIIC overexpression as a potential target in metastatic giant cell tumor.

We established two patient derived tumor cells (PDCs) from right and left pulmonary metastatic lesions respectively of a patient with giant cell tumor. At that time, patient-derived tumor cells from right and left surgical specimens were collected and cultured. High-throughput screening (HTS) for 24 drugs was conducted with a micropillar/microwell chip platform using giant cell tumor PDCs. Using 6 doses per drug in 6 replicates for giant cell tumor PDCs, the dose response curves and corresponding IC50 values were calculated from the scanned images using the S+ Chip Analyzer. A sensitive response was more significantly achieved for AZD4547 (FGFR2 inhibitor) in giant cell tumor PDCs originated from the right pulmonary nodule under the micropillar/microwell chip platform using 3D culture. This sensitivity was consistent with the target expression patterns of giant cell tumor PDCs (FGFR2-IIIC mRNA expression in giant cell tumor PDCs originated from the right pulmonary nodule was increased significantly as compared to those originated from left). However, in a conventional 2D cultured MTT assay, there was no difference for IC50 values of AZD4547 between giant cell tumor PDCs originated from right and left pulmonary nodules. An HTS platform based on 3D culture on micropillar/microwell chips and PDC models could be applied as a useful preclinical tool to evaluate the intrapatient tumor/response heterogeneity. This platform based on 3D culture might reflect far better the relation between the tumor-biology and the matched targeted agent as compared to a conventional 2D cultured MTT assay.

Tumor-induced Osteomalacia in a 3-Year-Old With Unresectable Central Giant Cell Lesions.

Tumor-induced osteomalacia (TIO) is a rare cause of hypophosphatemia involving overproduction of fibroblast growth factor 23. TIO has been described largely in adults with small mesenchymal tumors. We report a case of TIO in a child who presented with knee pain and radiographic findings concerning for rickets, and was found to have maxillomandibular giant cell lesions. The patient was treated with oral phosphorus and calcitriol, surgical debulking, and intralesional corticosteroids, which resulted in tumor regression and normalization of serum fibroblast growth factor 23 and phosphorus. This case illustrates the occurrence of this rare paraneoplastic syndrome in children and adds to our knowledge about clinical manifestations and pathologic findings associated with pediatric TIO.

Giant Cell Myocarditis: A Brief Review.

Giant cell myocarditis (GCM) is a rapidly progressive and frequently fatal disease that mainly affects young to middle-aged previously healthy individuals. Early diagnosis is critical, as recent studies have shown that rapidly instituted cyclosporine-based immunosuppression can reduce inflammation and improve transplant-free survival. Before the 1980s, GCM was mainly a diagnosis made at autopsy. Owing to advancements in diagnostic and therapeutic options, it is now increasingly diagnosed on the basis of endomyocardial biopsies, explanted hearts, or apical wedge sections removed at the time of ventricular assist device placement. Histologic examination remains the gold standard for diagnosis; however, there are many possible etiologies for cardiac giant cells. Having a working knowledge of the clinicopathologic features that distinguish GCM from other giant cell-containing lesions is essential, since such lesions can have widely divergent management and outcome.

Isolated limb perfusion as a treatment option for rare types of tumours.

BACKGROUND: Isolated limb perfusion (ILP) is an established and effective treatment for advanced melanoma and soft tissue sarcomas of the extremities with a high overall response rate. The aim of this study was to describe our experience of ILP for more rare types of tumours. METHODS: Patients with Merkel cell carcinoma (MCC) (n = 4), squamous cell carcinoma (SCC) (n = 2), B-cell lymphoma (n = 1), desmoid tumours (n = 3), pigmented villonodular synovitis (PVNS) (n = 1) and giant cell tumour (n = 1) were treated with ILP and analysed retrospectively. RESULTS: The four patients with in-transit MCC had three complete responses (CR) and one partial response (PR); the two patients with SCC had one CR and one stable disease (SD); the patients with desmoid tumours had two PR and one SD. A CR was also observed for the patient with a giant cell tumour, but the patient with PVNS had a SD. The patient with cutaneous metastases of B-cell lymphoma showed a CR, however with rapid systemic progression. Local toxicity according to Wieberdink was grade II in 10 patients (83%) and grade III in two patients (17%). CONCLUSIONS: These results show that ILP can be used as a treatment option also for more rare disease entities when other treatments have failed.

Role of Denosumab in Endoscopic Endonasal Treatment for Juvenile Clival Giant Cell Tumor: A Case Report and Review of the Literature.

BACKGROUND: Giant cell tumors (GCTs) are histologically benign bone neoplasms with a locally aggressive nature that primarily occur in the epiphyses of the long bones. A small proportion of these tumors, however, occur in the pelvis, spine, or skull bones. Among these, GCTs of the skull base cannot be completely resected and require adjuvant therapy. We report a juvenile case of clival GCT that was successfully treated by endoscopic endonasal transsphenoidal surgery and subsequent adjuvant therapy with denosumab, a monoclonal antibody to receptor activator of nuclear factor-κB ligand. CASE DESCRIPTION: A 16-year-old boy was admitted to our hospital with progressively intolerable headache and right oculomotor nerve palsy. Computed tomography and magnetic resonance imaging showed a large tumor mass in the sphenoid sinus with extensive erosion of the clivus and compression of the right cavernous sinus. The tumor was resected by endonasal transsphenoidal surgery and histologically diagnosed as GCT. The giant cells showed positive immunostaining for CD68 and Mib-1 labeling index was less than 1.0%. Postoperative course was uneventful and the oculomotor disturbance was markedly improved. However, magnetic resonance imaging 2 weeks after surgery revealed marked enlargement of the tumor. Adjuvant therapy with denosumab was therefore initiated, resulting in marked reductions in tumor size. CONCLUSIONS: This is the first report to describe beneficial effects of denosumab in the treatment of GCT of the skull base.

Current Systemic Treatment Options for Tenosynovial Giant Cell Tumor/Pigmented Villonodular Synovitis: Targeting the CSF1/CSF1R Axis.

OPINION STATEMENT: Adequate surgical resection remains the treatment of choice for tenosyovial giant cell tumor (TGCT). However, diffuse type TGCT (D-TGCT) is more difficult to resect and has a higher rate of recurrence (up to 50 %), which is often multiple. D-TGCT is rarely lethal and only rare cases of metastases have been described. Nevertheless, patients might have a significant decline in their quality of life due to multiple operations, which may sometimes result in a partial loss of function of the affected joint and may also be associated with perioperative morbidity and secondary arthrosis. As of today, no systemic treatment is approved for this rare disease. The aims of systemic therapy in the context of a non-lethal tumor are to reduce surgical morbidity and to preserve function and patient quality of life. Because TGCT is associated with characteristic cytogenetic abnormalities resulting in the overexpression of CSF1, systemic therapies targeting the CSF1/CSF1R axis (imatinib, nilotinib, emactuzumab, and PLX3397) have been tested in patients with locally advanced or relapsed D-TGCT. The more recent and more specific CSF1R inhibitors have shown a very interesting clinical activity with acceptable toxicity in early phase trials. These results will need to be confirmed in larger, ideally randomized, trials. But the high rate of clinical and functional improvement seen in some patients with advanced D-TGCT, often after multiple operations, suggests that these inhibitors will likely have a role in the management of patients with an inoperable disease; the definition of "inoperable TGCT" still requires refinement to reach a consensus. Another point that will need to be addressed is that of "the optimal duration of therapy" for these patients. Indeed, we and others have observed often prolonged clinical benefit and symptomatic relief even after treatment was stopped, with both monoclonal antibodies and tyrosine kinase inhibitors. Responses were observed very early on with emactuzumab and PLX3397, and patients experienced significant symptom improvement within a few weeks of starting therapy (2-4 weeks). Another possible application of CSF1R inhibitors could be used either as a preoperative or postoperative therapy for patients with operable TGCT. However, we currently lack sufficient follow-up to adequately address these questions which will each require specific trial designs. Overall, the striking clinical activity of CSF1R specific inhibitors in TGCT has created great enthusiasm among clinicians, and further development of these agents is clearly medically needed. Nevertheless, further investigations are necessary to validate those treatments and assess how to best incorporate them among other treatment modalities into the overall therapeutic strategy for a given patient.

CSF1R inhibition with emactuzumab in locally advanced diffuse-type tenosynovial giant cell tumours of the soft tissue: a dose-escalation and dose-expansion phase 1 study.

BACKGROUND: Diffuse-type tenosynovial giant cell tumour (dt-GCT) of the soft tissue (alternatively known as pigmented villonodular synovitis), an orphan disease with unmet medical need, is characterised by an overexpression of colony-stimulating factor 1 (CSF1), and is usually caused by a chromosomal translocation involving CSF1. CSF1 receptor (CSF1R) activation leads to the recruitment of CSF1R-expressing cells of the mononuclear phagocyte lineage that constitute the tumor mass in dt-GCT. Emactuzumab (RG7155) is a novel monoclonal antibody that inhibits CSF1R activation. We have assessed the safety, tolerability and activity of emactuzumab in patients with Dt-GCT of the soft tissue. METHODS: In this phase 1, first-in-human dose-escalation and dose-expansion study, eligible patients were aged 18 years or older with dt-GCT of the soft tissue with locally advanced disease or resectable tumours requiring extensive surgery, an Eastern Cooperative Oncology Group performance status of 1 or less, measurable disease according to Response Evaluation Criteria In Solid Tumors version 1.1, and adequate end-organ function. Patients with GCT of the bone were not eligible. Patients received intravenous emactuzumab at 900 mg, 1350 mg, or 2000 mg every 2 weeks in the dose-escalation phase and at the optimal biological dose in a dose-expansion phase. The primary objective was to evaluate the safety and tolerability of emactuzumab, and to determine the maximum tolerated dose or optimal biological dose. All treated patients were included in the analyses. Expansion cohorts are currently ongoing. This study is registered with ClinicalTrials.gov, number NCT01494688. FINDINGS: Between July 26, 2012, and Oct 21, 2013, 12 patients were enrolled in the dose-escalation phase. No dose-limiting toxicities were noted in the dose-escalation cohort; on the basis of pharmacokinetic, pharmacodynamic, and safety information, we chose a dose of 1000 mg every 2 week for the dose-expansion cohort, into which 17 patients were enrolled. Owing to different cutoff dates for safety and efficacy readouts, the safety population comprised 25 patients. Common adverse events after emactuzumab treatment were facial oedema (16 [64%] of 25 patients), asthenia (14 [56%]), and pruritus (14 [56%]). Five serious adverse events (periorbital oedema, lupus erythematosus [occurring twice], erythema, and dermohypodermitis all experienced by one [4%] patient each) were reported in five patients. Three of the five serious adverse events-periorbital oedema (one [4%]), lupus erythematosus (one [4%]), and dermohypodermitis (one [4%])-were assessed as grade 3. Two other grade 3 events were reported: mucositis (one [4%]) and fatigue (one [4%]). 24 (86%) of 28 patients achieved an objective response; two (7%) patients achieved a complete response. INTERPRETATION: Further study of dt-GCT is warranted and different possibilities, such as an international collaboration with cooperative groups to assure appropriate recruitment in this rare disease, are currently being assessed. FUNDING: F Hoffmann-La Roche.

Structure-Guided Blockade of CSF1R Kinase in Tenosynovial Giant-Cell Tumor.

BACKGROUND: Expression of the colony-stimulating factor 1 (CSF1) gene is elevated in most tenosynovial giant-cell tumors. This observation has led to the discovery and clinical development of therapy targeting the CSF1 receptor (CSF1R). METHODS: Using x-ray co-crystallography to guide our drug-discovery research, we generated a potent, selective CSF1R inhibitor, PLX3397, that traps the kinase in the autoinhibited conformation. We then conducted a multicenter, phase 1 trial in two parts to analyze this compound. In the first part, we evaluated escalations in the dose of PLX3397 that was administered orally in patients with solid tumors (dose-escalation study). In the second part, we evaluated PLX3397 at the chosen phase 2 dose in an extension cohort of patients with tenosynovial giant-cell tumors (extension study). Pharmacokinetic and tumor responses in the enrolled patients were assessed, and CSF1 in situ hybridization was performed to confirm the mechanism of action of PLX3397 and that the pattern of CSF1 expression was consistent with the pathological features of tenosynovial giant-cell tumor. RESULTS: A total of 41 patients were enrolled in the dose-escalation study, and an additional 23 patients were enrolled in the extension study. The chosen phase 2 dose of PLX3397 was 1000 mg per day. In the extension study, 12 patients with tenosynovial giant-cell tumors had a partial response and 7 patients had stable disease. Responses usually occurred within the first 4 months of treatment, and the median duration of response exceeded 8 months. The most common adverse events included fatigue, change in hair color, nausea, dysgeusia, and periorbital edema; adverse events rarely led to discontinuation of treatment. CONCLUSIONS: Treatment of tenosynovial giant-cell tumors with PLX3397 resulted in a prolonged regression in tumor volume in most patients. (Funded by Plexxikon; ClinicalTrials.gov number, NCT01004861.).

Giant cell tumors of the spine: has denosumab changed the treatment paradigm?

OBJECT Giant cell tumors (GCTs) of the spine are rare and complex to treat. They have a propensity for local recurrence and the potential to metastasize. Treatment is currently surgical and presents unique challenges due to the proximity of neural structures and the need for reconstruction. Denosumab has been shown in clinical trials to be an effective treatment for GCT, but has not yet been studied specifically in GCT of the spine or as a surgical adjunct. To the authors' knowledge this is the first such reported series. METHODS A multicenter, prospective series of 5 patients with GCT of the spine treated with denosumab were included. Patient demographic data, oncological history, neurological status, tumor staging, treatment details and adverse events, surgical procedure, complications, radiological and histological responses, and patient outcome were analyzed. RESULTS All patients were women, with a mean age of 38 years, and presented with pain; 2 patients had additional neurological signs and symptoms. The mean duration of symptoms was 62 weeks. No patient had a prior tumor or metastatic disease at presentation. All patients had Enneking Stage III tumors and were treated with monthly cycles of 120 mg of denosumab, with initial additional loading doses on Days 8 and 15. Patients were given daily supplements of calcium (500 mg) and vitamin D (400 IU). There were no denosumab-related adverse events. All patients had a radiological response to denosumab. One patient failed to have a histological response to denosumab, with > 90% of tumor cells found to be viable on histological investigation. CONCLUSIONS This study reports the early experience of using denosumab in the treatment of spinal GCT. The results demonstrate a clinically beneficial radiological response and an impressive histological response in most but not all patients. Further experience with denosumab and longer patient follow-up is required. Denosumab has the potential to change the treatment paradigm for spinal GCT.

Stage 0 osteonecrosis of the jaw in a patient on denosumab.

Osteonecrosis of the jaws (ONJ) is a complex disease involving multiple tissue and cell-type responses to wound healing or infection. AAOMS defines bisphosphonate related ONJ (BRONJ) as exposed, necrotic bone in the maxillofacial region that has persisted for more than 8 weeks in a patient with current or previous antiresorptive treatment, without a history of radiation therapy to the jaws. Since the first reported ONJ cases in 2003 and 2004, there has been little advancement in understanding the etiology and pathophysiology of ONJ. Many hypotheses have been proposed, including bisphosphonate (BP) toxicity to oral epithelium, altered wound healing after tooth extraction, high turnover of the mandible and maxilla, oral biofilm formation, infection and inflammation, and suppression of angiogenesis and bone turnover. The current classification system of ONJ involves stages 0 to 3 and is based on patient clinical presentation. This report describes a case of stage 0 ONJ in a patient on denosumab and indicates the full-spectrum similarities between BP- and denosumab-associated ONJ clinically, radiographically, and histologically.