Long-term efficacy of imatinib mesylate in patients with advanced Tenosynovial Giant Cell Tumor

Vimseltinib versus placebo for tenosynovial giant cell tumour (MOTION): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Tenosynovial giant cell tumour (TGCT) is a locally aggressive neoplasm for which few systemic treatment options exist. This study evaluated the efficacy and safety of vimseltinib, an oral, switch-control, CSF1R inhibitor, in patients with symptomatic TGCT not amenable to surgery.

METHODS

MOTION is a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial done in 35 specialised hospitals in 13 countries. Eligible patients were adults (aged ≥18 years) with a histologically confirmed diagnosis of TGCT for which surgical resection could potentially worsen functional limitation or cause severe morbidity. Patients were randomly assigned (2:1) with interactive response technology to vimseltinib (30 mg orally twice weekly) or placebo, administrated in 28-day cycles for 24 weeks. Patients and site personnel were masked to treatment assignment until week 25, unless progressive disease was confirmed earlier. The primary endpoint was objective response rate by independent radiological review using Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST) at week 25 in the intention-to-treat population. Safety was assessed in all patients who received the study drug. The trial is registered with ClinicalTrials.gov, NCT05059262, and enrolment is complete.

FINDINGS

Between Jan 21, 2022, and Feb 21, 2023, 123 patients were randomly assigned (83 to vimseltinib and 40 to placebo). 73 (59%) patients were female and 50 (41%) were male. Nine (11%) of 83 patients assigned to vimseltinib and five (13%) of 40 patients assigned to placebo discontinued treatment before week 25; one patient in the placebo group did not receive any study drug. Objective response rate per RECIST was 40% (33 of 83 patients) in the vimseltinib group vs 0% (none of 40) in the placebo group (difference 40% [95% CI 29-51]; p<0·0001). Most treatment-emergent adverse events (TEAEs) were grade 1 or 2; the only grade 3 or 4 TEAE that occurred in more than 5% of patients receiving vimseltinib was increased blood creatine phosphokinase (eight [10%] of 83). One patient in the vimseltinib group had a treatment-related serious TEAE of subcutaneous abscess. No evidence of cholestatic hepatotoxicity or drug-induced liver injury was noted.

INTERPRETATION

Vimseltinib produced a significant objective response rate and clinically meaningful functional and symptomatic improvement in patients with TGCT, providing an effective treatment option for these patients.

FUNDING

Deciphera Pharmaceuticals.

Total knee arthroplasty in pigmented villonodular synovitis osteoarthritis: a systematic review of literature

PURPOSE

Pigmented Villonodular Synovitis (PVNS) is a proliferative disease arising from the synovial membrane, mainly affects large joints such as the knee (almost 80% of total). Prostheses implanted in PVNS osteoarthritis show a higher revision rate when compared to primary osteoarthritis, due to the recurrence of disease and the overall surgical complications. The purpose of this systematic review is to summarize and compare indications, clinical and functional outcomes, disease-related and surgical-related complications of total knee arthroplasty in PVNS osteoarthritis.

MATERIALS AND METHODS

A systematic review of the literature was performed with a primary search on Medline through PubMed. The PRISMA 2009 flowchart and checklist were used to edit the review. Screened studies had to provide preoperative diagnosis, previous treatments, main treatment, concomitant strategies, mean follow-up, outcomes and complications to be included in the review.

RESULTS

A total of 8 articles were finally included. Most of papers reported the use of non-constrained design implants, mainly posterior stabilized (PS) and in case of PVNS with extensive joint involvement implants with higher degree of constraint to obtain a fulfilling balancing. Recurrence of PVNS has been indicated as the major complication, followed by aseptic loosening of the implant and difficult post-operative course with an increased risk of stiffness.

CONCLUSION

Total knee arthroplasty represents a valid treatment for patients with PVNS end-stage osteoarthritis, with good clinical and functional results, even in longer follow-up. It would be advisable a multidisciplinary management and a meticulous rehabilitation and monitoring following the procedure, to reduce the emergence of recurrence and overall complications.

Keratin-Positive Giant Cell Tumor of Bone and Soft Tissue With HMGA2::NCOR2 Fusion in Children Under 10 With Response to Imatinib Therapy: A Case Series

HMGA2::NCOR2 keratin-positive giant cell tumors in children with response to imatinib in an infant.

Precision Oncology in Soft Tissue Sarcomas and Gastrointestinal Stromal Tumors

Soft tissue sarcomas (STSs), including gastrointestinal stromal tumors (GISTs), are mesenchymal neoplasms with heterogeneous clinical behavior and represent broad categories comprising multiple distinct biologic entities. Multidisciplinary management of these rare tumors is critical. To date, multiple studies have outlined the importance of biological characterization of mesenchymal tumors and have identified key molecular alterations which drive tumor biology. GIST has represented a flagship for targeted therapy in solid tumors with the advent of imatinib which has revolutionized the way we treat this malignancy. Herein, the authors discuss the importance of biological and molecular diagnostics in managing STS and GIST patients.

Real-world drug utilization and treatment patterns in patients with tenosynovial giant cell tumors in the USA

Aim: Real-world treatment patterns in tenosynovial giant cell tumor (TGCT) patients remain unknown. Pexidartinib is the only US FDA-approved treatment for TGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. Objective: To characterize drug utilization and treatment patterns in TGCT patients. Methods: In a retrospective observational study using IQVIA's linked prescription and medical claims databases (2018-2021), TGCT patients were stratified by their earliest systemic therapy claim (pexidartinib [N = 82] or non-FDA-approved systemic therapy [N = 263]). Results: TGCT patients treated with pexidartinib versus non-FDA-approved systemic therapies were predominantly female (61 vs 50.6%) and their median age was 47 and 54 years, respectively. Pexidartinib-treated patients had the highest 12-month probability of remaining on treatment (54%); 34.1% of pexidartinib users had dose reduction after their first claim. Conclusion: This study provides new insights into the unmet need, utilization and treatment patterns of systemic therapies for the treatment of TGCT patients.

Recurrence-Free Survival after Synovectomy and Subsequent Radiosynoviorthesis in Patients with Synovitis of the Knee-A Retrospective Data Analysis

BACKGROUND

Persistent knee synovitis leads to joint discomfort, incapacitating inflammation, and functional limitations. The conventional approach has involved surgical procedures to eliminate the actively inflamed synovial membrane. This study aims to investigate the recurrence-free survival and functional outcome after synovectomy and subsequent radiosynoviorthesis (RSO) in patients with knee synovitis.

METHODS

Thirty-seven knees diagnosed with pigmented villonodular synovitis (PVNS), rheumatoid arthritis (RA), and peripheral spondyloarthritis underwent synovectomy and subsequent RSO between May 2005 and October 2016. The mean age was 34.9 ± 15.1 years, and the mean follow-up period was 84 ± 36.4 months. Clinical outcomes were assessed using the Oxford Knee Score and the presence of swelling and pain at the last follow-up. Recurrence-free survival denotes the duration from synovectomy to surgical re-synovectomy.

RESULTS

In general, twelve knees underwent re-synovectomy after a mean follow-up of 34.8 ± 24.9 months. The recurrence-free survival was 83.8% at two years, 71.3% at five years, and 61.7% at ten years. The subgroup analysis revealed recurrence-free survival at two years in 63.6% of patients with PVNS, 86.7% of those with RA, and 100% of individuals with peripheral spondyloarthritis.

CONCLUSIONS

This study demonstrates that combined therapy for synovitis is an effective approach, significantly improving clinical outcomes.

Tenosynovial giant cell tumor: a case report

BACKGROUND

This case reports the synchronous diagnosis of two rare unrelated diseases; leiomyosarcoma and tenosynovial giant cell tumor of the knee. It focuses on the challenges of diagnosing tenosynovial giant cell tumor, including cognitive biases in clinical medicine that delay diagnosis. It also demonstrates the pathogenic etiology of tenosynovial giant cell tumor, evidenced by the transient deterioration of the patients' knee symptoms following the administration of prophylactic granulocyte colony-stimulating factor given as part of the chemotherapeutic regime for leiomyosarcoma.

CASE PRESENTATION

A 37-year-old Caucasian man presented with a left groin lump and left knee pain with swelling and locking. Investigations including positron emission tomography-computed tomography and biopsy revealed leiomyosarcoma in a lymph node likely related to the spermatic cord, with high-grade uptake in the left knee that was presumed to be the primary site. His knee symptoms temporarily worsened each time granulocyte colony-stimulating factor was administered with each cycle of chemotherapy for leiomyosarcoma to help combat myelosuppressive toxicity. Subsequent magnetic resonance imaging and biopsy of the knee confirmed a tenosynovial giant cell tumor. His knee symptoms relating to the tenosynovial giant cell tumor improved following the completion of his leiomyosarcoma treatment.

CONCLUSIONS

Tenosynovial giant cell tumor remains a diagnostic challenge. We discuss the key clinical features and investigations that aid prompt diagnosis. The National Comprehensive Cancer Network clinical practice guidelines for soft tissue sarcoma have recently been updated to include the pharmacological management of tenosynovial giant cell tumor. Our case discussion provides an up-to-date review of the evidence for optimal management of patients with tenosynovial giant cell tumor, with a particular focus on novel pharmacological options that exploit underlying pathogenesis.

Diffuse-type tenosynovial giant cell tumor between the suboccipital bone and posterior C1 arch: illustrative case

BACKGROUND

Tenosynovial giant cell tumor (TGCT) occurs most commonly in the appendicular skeleton and is only rarely found in the vertebral column. Lesions of the craniocervical junction are particularly rare, with only 4 cases reported in the literature. The authors describe the case of a diffuse-type TGCT at the craniocervical junction.

OBSERVATIONS

A patient presented with a 1-year history of right-sided neck pain and bilateral neurological symptoms in the distribution of the right occipital nerve. A 20-mm homogeneously contrast-enhancing mass in the suboccipital and posterior C1 region was discovered on magnetic resonance imaging of the cervical spine. The tumor was operated on via a posterior approach, and gross-total resection (GTR) was achieved. Immunohistochemical (IHC) examination revealed a diffuse-type TGCT. The patient had an uneventful recovery.

LESSONS

TGCT can arise at the craniocervical junction and is easily misdiagnosed because of its rare occurrence. IHC examination of a tumor specimen should be done to confirm the diagnosis. GTR is the objective when treating these tumors, especially when they are the diffuse type, as they have a high recurrence rate. Radiation and small-molecule therapies are viable postoperative therapies if GTR cannot be achieved or in cases of recurrence.

Current therapies and future prospective for locally aggressive mesenchymal tumors

Locally aggressive mesenchymal tumors comprise a heterogeneous group of soft tissue and bone tumors with intermediate histology, incompletely understood biology, and highly variable natural history. Despite having a limited to absent ability to metastasize and excellent survival prognosis, locally aggressive mesenchymal tumors can be symptomatic, require prolonged and repeat treatments including surgery and chemotherapy, and can severely impact patients' quality of life. The management of locally aggressive tumors has evolved over the years with a focus on minimizing morbid treatments. Extensive oncologic surgeries and radiation are pillars of care for high grade sarcomas, however, play a more limited role in management of locally aggressive mesenchymal tumors, due to propensity for local recurrence despite resection, and the risk of transformation to a higher-grade entity following radiation. Patients should ideally be evaluated in specialized sarcoma centers that can coordinate complex multimodal decision-making, taking into consideration the individual patient's clinical presentation and history, as well as any available prognostic factors into customizing therapy. In this review, we aim to discuss the biology, clinical management, and future treatment frontiers for three representative locally aggressive mesenchymal tumors: desmoid-type fibromatosis (DF), tenosynovial giant cell tumor (TSGCT) and giant cell tumor of bone (GCTB). These entities challenge clinicians with their unpredictable behavior and responses to treatment, and still lack a well-defined standard of care despite recent progress with newly approved or promising experimental drugs.

Giant cell tumor of tendon sheath: A report of 216 cases

BACKGROUND

In this article on giant cell tumor of tendon sheath (GCTTS), we intend to summarize and analyze the clinical and pathological features of GCTTS hoping to improve clinical management and patient treatment.

METHODS

The study retrospectively reviewed 216 patients of GCTTS, registered at the Affiliated Hospital of Southwest Medical University from January 2010 to December 2020. These cases were diagnosed by surgical excision. The clinicopathological features and the prognosis were reviewed in the light of the current literature.

RESULTS

Of these 216 GCTTS patients, 72 were males (33.3%) and 144 females (66.7%), with a ratio male-to-female of 1:2. The patients' age ranged from 5 to 82, the average being 41.5 years at diagnosis. A total of 96 cases (44.4%) occurred in the hand region, followed by 35 cases (16.2%) in the knee, 32 cases (14.8%) in the foot, 25 cases (11.6%) in the ankle, 12 cases (5.6%) in the wrist, 12 cases (5.6%) in the leg, 2 cases (0.9%) in the head, 1 case (0.5%) in the forearm, and 1 case (0.5%) inside and outside the spinal channel. Histopathology mainly revealed large synovial-like monocytes, small monocytes, and osteoclast-like giant cells.

CONCLUSION

Our results confirm that GCTTS predominantly occurs in the hands of young women. Complete surgical resection with long-term follow-up is the preferred management.

One-Stage Synovectomies Result in Improved Short-Term Outcomes Compared to Two-Stage Synovectomies of Diffuse-Type Tenosynovial Giant Cell Tumor (D-TGCT) of the Knee: A Multicenter, Retrospective, Cohort Study

Diffuse-type tenosynovial giant cell tumors' (D-TGCTs) intra- and extra-articular expansion about the knee often necessitates an anterior and posterior surgical approach to facilitate an extensive synovectomy. There is no consensus on whether two-sided synovectomies should be performed in one or two stages. This retrospective study included 191 D-TGCT patients from nine sarcoma centers worldwide to compare the postoperative short-term outcomes between both treatments. Secondary outcomes were rates of radiological progression and subsequent treatments. Between 2000 and 2020, 117 patients underwent one-stage and 74 patients underwent two-stage synovectomies. The maximum range of motion achieved within one year postoperatively was similar (flexion 123-120°, p = 0.109; extension 0°, p = 0.093). Patients undergoing two-stage synovectomies stayed longer in the hospital (6 vs. 4 days, p < 0.0001). Complications occurred more often after two-stage synovectomies, although this was not statistically different (36% vs. 24%, p = 0.095). Patients treated with two-stage synovectomies exhibited more radiological progression and required subsequent treatments more often than patients treated with one-stage synovectomies (52% vs. 37%, p = 0.036) (54% vs. 34%, p = 0.007). In conclusion, D-TGCT of the knee requiring two-side synovectomies should be treated by one-stage synovectomies if feasible, since patients achieve a similar range of motion, do not have more complications, but stay for a shorter time in the hospital.

Best clinical management of tenosynovial giant cell tumour (TGCT): A consensus paper from the community of experts

Tenosynovial giant cell tumour (TGCT) is a rare, locally aggressive, mesenchymal tumor arising from the joints, bursa and tendon sheaths. TGCT comprises a nodular- and a diffuse-type, with the former exhibiting mostly indolent course and the latter a locally aggressive behavior. Although usually not life-threatening, TGCT may cause chronic pain and adversely impact function and quality of life (QoL). CSFR1 inhibitors are effective with benefit on symptoms and QoL but are not available in most countries. The degree of uncertainty in selecting the most appropriate therapy and the lack of guidelines on the clinical management of TGCT make the adoption of new treatments inconsistent across the world, with suboptimal outcomes for patients. A global consensus meeting was organized in June 2022, involving experts from several disciplines and patient representatives from SPAGN to define the best evidence-based practice for the optimal approach to TGCT and generate the recommendations presented herein.

Novel CSF1R-positive tenosynovial giant cell tumor cell lines and their pexidartinib (PLX3397) and sotuletinib (BLZ945)-induced apoptosis

Tenosynovial giant cell tumor (TGCT) is a mesenchymal tumor derived from the synovium of the tendon sheath and joints, most frequently in the large joints. The standard of care for TGCTs is surgical resection. A new targeting approach for treating TGCTs has emerged from studies on the role of the CSF1/CSF1 receptor (CSF1R) in controlling cell survival and proliferation during the pathogenesis of TGCTs. We established four novel cell lines isolated from the primary tumor tissues of patients with TGCTs. The cell lines were designated Si-TGCT-1, Si-TGCT-2, Si-TGCT-3, and Si-TGCT-4, and the TGCT cells were characterized by CSF1R and CD68. These TGCT cells were then checked for cell proliferation using an MTT assay and three-dimensional spheroid. The responses to pexidartinib (PLX3397) and sotuletinib (BLZ945) were evaluated by two-dimensional MTT assays. All cells were positive for α‑smooth muscle actin (α‑SMA), fibroblast activation protein (FAP), CSF1R, and CD68. Except for Si-TGCT-4, all TGCT cells had high CSF1R expressions. The cells exhibited continuous growth as three-dimensional spheroids formed. Treatment with pexidartinib and sotuletinib inhibited TGCT cell growth and induced cell apoptosis correlated with the CSF1R level. Only Si-TGCT-4 cells demonstrated resistance to the drugs. In addition, the BAX/BCL-2 ratio increased in cells treated with pexidartinib and sotuletinib. With the four novel TGCT cell lines, we have an excellent model for further in vitro and in vivo studies.

Pexidartinib Provides Modest Pain Relief in Patients With Tenosynovial Giant Cell Tumor: Results From ENLIVEN

BACKGROUND

The double-blind, randomized, placebo-controlled phase 3 study of orally administered PLX3397 in patients with pigmented villonodular synovitis or giant cell tumor of the tendon sheath (ENLIVEN) showed that pexidartinib provides a robust objective tumor response in adults with tenosynovial giant cell tumors (TGCT) not amenable to improvement with surgery. Based on these results, in 2019, pexidartinib received accelerated approval in the United States in this population as a breakthrough therapy under an orphan drug designation. However, the ability of pexidartinib to relieve pain in ENLIVEN was not fully detailed, and the relationship between pain relief and objective tumor response was not described.

QUESTIONS/PURPOSES

(1) What level of pain relief was achieved by pexidartinib treatment in ENLIVEN? (2) How was pain relief related to objective tumor responses? (3) How durable was pain relief?

METHODS

The current study included planned primary and exploratory assessments of patient-assessed worst pain at the site of the tumor in the ENLIVEN trial. ENLIVEN was a phase 3 randomized, placebo-controlled clinical trial in which adults with TGCT not amenable to improvement with surgery received pexidartinib or placebo for 24 weeks, after which eligible patients could receive open-label pexidartinib. Of 174 patients assessed for eligibility, 121 were randomized (50% [60] to placebo, 50% [61] to pexidartinib), and 120 were given either placebo or pexidartinib (59 received placebo and 61 received pexidartinib) and were included in an intent-to-treat analysis. Fifty-nine percent (71 of 120) of the overall treated population was female, and 88% (106 of 120) were White. Mean age was 45 ± 13 years. Tumors were mostly in the lower extremities (92% [110 of 120]), most commonly in the knee (61% [73 of 120]) and ankle (18% [21 of 120]). As a secondary outcome, patients scored worst pain at the site of the tumor in the past 24 hours on an 11-point numeric rating scale (NRS). The primary definition of a pain response was a decrease of at least 30% in the weekly mean worst-pain NRS score and increase of less than 30% in narcotic analgesic use between baseline and week 25. Planned exploratory assessments of pain included the frequency of a pain response using alternative thresholds, including a decrease in worst-pain NRS score of 50% or more and a decrease of at least 2 points (minimum clinically important difference [MCID]), the magnitude of pain reduction between baseline and week 25, correlation between worst-pain NRS score and tumor shrinkage by RECIST 1.1 criteria, and the durability of the pain response during the open-label extension. Pain responses during the randomized portion of the trial were compared according to intention-to-treat analysis, with a one-sided threshold of p < 0.025 to reduce the risk of false-positive results. Pain assessment was complete for 59% (35 of 59) of patients in the placebo group and 54% (33 of 61) of patients in the pexidartinib group. Demographic and disease characteristics did not differ between the two treatment groups.

RESULTS

A difference in the primary assessment of a pain response was not detected between pexidartinib and placebo (response percentage 31% [19 of 61] [95% CI 21% to 44%] versus 15% [9 of 59] [95% CI 8% to 27%]; one-sided p = 0.03). In the exploratory analyses, pexidartinib provided a modest improvement in pain (response percentage 26% [16 of 61] [95% CI 17% to 38%] versus 10% [6 of 59] [95% CI 5% to 20%]; one-sided p = 0.02 using the 50% threshold and 31% [19 of 61] [95% CI 21% to 44%] versus 14% [8 of 59] [95% CI 7% to 25%]; one-sided p = 0.02 using the MCID threshold). The least-squares mean change in the weekly mean worst-pain NRS score between baseline and week 25 was larger in patients treated with pexidartinib than placebo (-2.5 [95% CI -3.0 to -1.9] versus -0.3 [95% CI -0.9 to 0.3]; p < 0.001), although the mean difference between the two groups (-2.2 [95% CI -3.0 to -1.4]) was just over the MCID. Improvement in the weekly mean worst-pain NRS score correlated with the reduction in tumor size (r = 0.44; p < 0.001) and tumor volume score (r = 0.61; p < 0.001). For patients in the open-label extension, the change in the worst-pain NRS score from baseline was similar to the change at the end of the randomized portion and just above the MCID (mean -2.7 ± 2.2 after 25 weeks and -3.3 ± 1.7 after 50 weeks of receiving pexidartinib).

CONCLUSION

Based on the current study, a modest reduction in pain, just larger than the MCID, may be an added benefit of pexidartinib in these patients, although the findings are insufficient to justify the routine use of pexidartinib for pain relief.

LEVEL OF EVIDENCE

Level II, therapeutic study.

A prospective real-world study of the diffuse-type tenosynovial giant cell tumor patient journey: A 2-year observational analysis

BACKGROUND AND OBJECTIVES

Diffuse-tenosynovial giant cell tumor (D-TGCT) is a rare, locally aggressive, typically benign neoplasm affecting mainly large joints, representing a wide clinical spectrum. We provide a picture of the treatment journey of D-TGCT patients as a 2-year observational follow-up.

METHODS

The TGCT Observational Platform Project registry was a multinational, multicenter, prospective observational study at tertiary sarcoma centers spanning seven European countries and two US sites. Histologically confirmed D-TGCT patients were categorized as either those who remained on initial treatment strategy (determined at baseline visit) or those who changed treatment strategy with specific changes documented (e.g., systemic treatment to surgery) at the 1-year and/or 2-year follow-up visits.

RESULTS

A total of 176 patients were assessed, mean diagnosis age was 38.4 (SD ± 14.6) years; most patients had a knee tumor (120/176, 68.2%). For the 2-year observation period, most patients (75.5%) remained on the baseline treatment strategy throughout, 54/79 patients (68.4%) remained no treatment, 30/45 patients (66.7%) remained systemic treatment, 39/39 patients (100%) remained surgery. Those who changed treatment strategy utilized multimodal treatment options.

CONCLUSIONS

This is the first prospectively collected analysis to describe D-TGCT patient treatments over an extended follow-up and demonstrates the need for multidisciplinary teams to determine an optimal treatment strategy.

Interactions in CSF1-Driven Tenosynovial Giant Cell Tumors

PURPOSE

A major component of cells in tenosynovial giant cell tumor (TGCT) consists of bystander macrophages responding to CSF1 that is overproduced by a small number of neoplastic cells with a chromosomal translocation involving the CSF1 gene. An autocrine loop was postulated where the neoplastic cells would be stimulated through CSF1R expressed on their surface. Here, we use single-cell RNA sequencing (scRNA-seq) to investigate cellular interactions in TGCT.

EXPERIMENTAL DESIGN

A total of 18,788 single cells from three TGCT and two giant cell tumor of bone (GCTB) samples underwent scRNA-seq. The three TGCTs were additionally analyzed using long-read RNA sequencing. Immunofluorescence and IHC for a range of markers were used to validate and extend the scRNA-seq findings.

RESULTS

Two recurrent neoplastic cell populations were identified in TGCT that are highly similar to nonneoplastic synoviocytes. We identified GFPT2 as a marker that highlights the neoplastic cells in TCGT. We show that the neoplastic cells themselves do not express CSF1R. We identified overlapping MAB features between the giant cells in TGCT and GCTB.

CONCLUSIONS

The neoplastic cells in TGCT are highly similar to nonneoplastic synoviocytes. The lack of CSF1R on the neoplastic cells indicates they may be unaffected by current therapies. High expression of GFPT2 in the neoplastic cells is associated with activation of the YAP1/TAZ pathway. In addition, we identified expression of the platelet-derived growth factor receptor in the neoplastic cells. These findings suggest two additional pathways to target in this tumor.

Surgical management of 144 diffuse-type TGCT patients in a single institution: A 20-year cohort study

BACKGROUND AND OBJECTIVES

Surgery is the mainstay of treatment for tenosynovial giant cell tumors (TGCTs). However, achieving a cure through surgery alone remains challenging, especially for the diffuse-type (D-TGCT).

METHODS

Our goal was to describe the surgical management of patients with D-TGCT related to large joints, treated between 2000 and 2020. We analyzed the effect of (in)complete resections and the presence of postoperative tumor (POT) on magnetic resonance imaging (MRI) on radiological and clinical outcomes.

RESULTS

A total of 144 patients underwent open surgery for D-TGCT, of which 58 (40%) had treatment before. The median follow-up was 65 months. One hundred twenty-five patients underwent isolated open surgeries, in which 25 (20%) patients' D-TGCT was intentionally removed incompletely. POT presence on the first postoperative MRI was observed in 64%. Both incomplete resections and POT presence were associated with higher rates of radiological progression (73% vs. 44%; Kaplan-Meier [KM] analysis p = 0.021) and 59% versus 7%; KM analysis p < 0.001), respectively. Furthermore, patients with POT presence clinically worsened more often than patients without having POT (49% vs. 24%; KM analysis p = 0.003).

CONCLUSIONS

D-TGCT is often resected incompletely and tumor presence is commonly observed on the first postoperative MRI, resulting in worse radiological and clinical outcomes. Therefore, surgeons should try to remove D-TGCT in toto and consider other multimodal therapeutic strategies.

PD-L1 Status in Tenosynovial Giant Cell Tumors

Background and Objectives: Tenosynovial giant cell tumors (TSGCTs) are benign soft tissue tumors that are divided into localized- and diffuse-type tumors, according to the World Health Organization classification of soft tissue tumours. The diffuse-type TSGCT sometimes behave aggressively and poses treatment challenges especially in patients with neurovascular involvement. Symptomatic patients who are not good candidates for surgery due to high morbidity risk may benefit from medical therapy. Objectives: Drugs that target programmed death ligand 1 (PD-L1) are among a new generation of medical therapy options, which, recently, have been explored and have displayed promising results in various cancer types; therefore, we aimed to investigate the PD-L1 status of TSGCTs as a possible therapeutic target. Materials and Methods: We assessed the PD-L1 status of 20 patients (15 men and 5 women, median age = 39 years) that had been diagnosed with TSGCTs in a single institution, between 2018 and 2020. The patients had localized- (n = 7) and diffuse-type (n = 13) TSGCTs. Formalin-fixed paraffin-embedded (FFPE) blocks were retrospectively retrieved from the pathology department. An immunohistochemical analysis was performed in sections of 3 micron thickness from these blocks. Results: Seventy-five percent of our patients with TSGCTs were immunopositive to PD-L1 staining. Conclusions: Taking into consideration the high positivity rate of PD-L1 staining in TSGCTs, PD-L1 blockage may be used as a valuable medical treatment for TSGCTs; however, further studies are needed.

Long-term follow-up of nilotinib in patients with advanced tenosynovial giant cell tumours: Long-term follow-up of nilotinib in TGCT

BACKGROUND

Diffuse-type tenosynovial giant cell tumour (D-TGCT) is a non-malignant but locally aggressive tumour driven by overexpression of colony-stimulating factor-1 (CSF1). CSF1R inhibitors are potential therapeutic strategies for patients not amenable to surgery. We report here the long-term outcome of nilotinib in patients with advanced D-TGCT treated within a phase II prospective international study (ClinicalTrials.gov: NCT01261429).

METHODS

Patients were enrolled between December 2010-September 2012 at 11 cancer centres. Eligible patients had histologically confirmed D-TGCT, not amenable to surgery. Patients received nilotinib until evidence of progression, toxicity or a maximum of one year. Long-term data were retrospectively collected after the completion of the phase II trial. Patients with nilotinib treatment ≥12 weeks and follow-up ≥12 months were included for long-term analysis.

RESULTS

Forty-eight of 56 enrolled patients were included. Median treatment duration was 11 months; 31 (65%) patients completed the treatment protocol. After 102 months of follow-up (median; range 12-129), 25 patients (52%) had progression. The median progression-free survival (PFS) was 77 months. The five-year PFS rate was 53%. Fifteen patients (n = 15/46; 33%) experienced clinical worsening after 11 months (median). Twenty-seven patients (58%) received additional treatment, after which eleven patients (n = 11/27; 41%) had a second relapse. Nine patients required a subsequent treatment, primarily other CSF1R inhibitors (n = 6/9; 67%). No unfavourable long-term effects were observed.

CONCLUSION

This long-term analysis of nilotinib for advanced D-TGCT showed that about half of the patients had progression and underwent additional treatment after 8.5 years follow-up. Contrarily, several patients had ongoing disease control after limited treatment duration, demonstrating the mixed effect of nilotinib.

Treatment updates on tenosynovial giant cell tumor

PURPOSE OF REVIEW

Diffuse-type tenosynovial giant cell tumor (dt-TGCT) is a benign clonal neoplastic proliferation arising from the synovium. Patients are often symptomatic, require multiple surgical procedures during their lifetime, and have reduced quality of life (QoL). Surgery is the main treatment with relapse rates ranging from 14 to 55%. The treatment strategy for patients with dt-TGCT is evolving. The purpose of this review is to describe current treatment options, and to highlight recent developments in the knowledge of the molecular pathogenesis of dt-TGCT as well as related therapeutic implications.

RECENT FINDINGS

TGCT cells overexpress colony-stimulating factor 1 (CSF1), resulting in recruitment of CSF1 receptor (CSF1R)-bearing macrophages that are polyclonal and make up the bulk of the tumor, has led to clinical trials with CSF1R inhibitors. These inhibitors include small molecules such as pexidatinib, imatinib, nilotinib, DCC-3014 (vimseltinib), and the monoclonal antibody RG7155 (emactuzumab).

SUMMARY

In conclusion, D-TGCT impairs patients' QoL. The evidence that the pathogenetic loop of D-TGCT can be inhibited has changed the therapeutic armamentarium for this condition. Clinical trials of agents that target CSF1R are currently ongoing. All this new evidence should be taken into consideration within multidisciplinary management.

Tenosynovial giant cell tumors (TGCT): molecular biology, drug targets and non-surgical pharmacological approaches

INTRODUCTION

Tenosynovial giant cell tumor (TGCT) is a mono-articular, benign or locally aggressive and often debilitating neoplasm. Systemic therapies are becoming part of the multimodal armamentarium when surgery alone will not confer improvements. Since TGCT is characterized by colony-stimulating factor-1 (CSF1) rearrangements, the most studied molecular pathway is the CSF1 and CSF1 receptor (CSF1R) axis. Inhibiting CSF1-CSF1R interaction often yields considerable radiological and clinical responses; however, adverse events may cause treatment discontinuation because of an unfavorable risk-benefit ratio in benign disease. Only Pexidartinib is approved by the US FDA; however, the European Medicines Agency has not approved it due to uncertainties on the risk-benefit ratio. Thus, there is a need for safer and effective therapies.

AREAS COVERED

Light is shed on disease mechanisms and potential drug targets. The safety and efficacy of different systemic therapies are evaluated.

EXPERT OPINION

The CSF1-CSF1R axis is the principal drug target; however, the effect of CSF1R inhibition on angiogenesis and the role of macrophages, which are essential in the postoperative course, needs further elucidation. Systemic therapies have a promising role in treating mainly diffuse-type, TGCT patients who are not expected to clinically improve from surgery. Future drug development should focus on targeting neoplastic TGCT cells.

CSF1 receptor inhibition of tenosynovial giant cell tumor using novel disease-specific MRI measures of tumor burden

Aim: Monitoring treatment of tenosynovial giant cell tumor (TGCT) is complicated by the irregular shape and asymmetrical growth of the tumor. We compared responses to pexidartinib by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 with those by tumor volume score (TVS) and modified RECIST (m-RECIST). Materials & methods: MRIs acquired every two cycles were assessed centrally using RECIST 1.1, m-RECIST and TVS and tissue damage score (TDS). Results: Thirty-one evaluable TGCT patients were treated with pexidartinib. From baseline to last visit, 94% of patients (29/31) showed a decrease in tumor size (median change: -60% [RECIST], -66% [m-RECIST], -79% [TVS]). All methods showed 100% disease control rate. For TDS, improvements were seen in bone erosion (32%), bone marrow edema (58%) and knee effusion (46%). Conclusion: TVS and m-RECIST offer potentially superior alternatives to conventional RECIST for monitoring disease progression and treatment response in TGCT. TDS adds important information about joint damage associated with TGCT.

Imatinib, a New Adjuvant Medical Treatment for Multifocal Villonodular Synovitis Associated to Noonan Syndrome: A Case Report and Literature Review

Noonan syndrome (NS) is an autosomal dominant multisystem disorder caused by the dysregulation of the Rat Sarcoma/Mitogen-activated protein kinase (RAS/MAPK) pathway and characterized by short stature, heart defects, pectus excavatum, webbed neck, learning disabilities, cryptorchidism, and facial dysmorphia. Villonodular synovitis is a joint disorder most common in young adults characterized by an abnormal proliferation of the synovial membrane. Multifocal Villonodular synovitis is a rare disease whose recurrent nature can make its management particularly difficult. Currently, there is no systemic therapy recommended in diffuse and recurrent forms, especially because of the fear of long-term side effects in patients, who are usually young. Yet, tyrosine kinase inhibitors seem promising to reduce the effects of an aberrant colony stimulating factor-1 (CSF-1) production at the origin of the synovial nodule proliferation. We present here the case of a 21-year-old woman with NS associated to diffuse multifocal villonodular synovitis (DMVS). Our clinical case provides therapeutic experience in this very rare association. Indeed, in association with surgery, the patient improved considerably: she had complete daily life autonomy, knee joint amplitudes of 100° in flexion and 0° in extension and was able to walk for 10 min without any technical assistance. To our knowledge, this is the first case of a patient suffering from DMVS associated with a Noonan syndrome treated with Glivec® (oral administration at a dosage of 340 mg/m2 in children, until disease regression) on a long-term basis.

Results from Phase I Extension Study Assessing Pexidartinib Treatment in Six Cohorts with Solid Tumors including TGCT, and Abnormal CSF1 Transcripts in TGCT

PURPOSE

To assess the response to pexidartinib treatment in six cohorts of adult patients with advanced, incurable solid tumors associated with colony-stimulating factor 1 receptor (CSF1R) and/or KIT proto-oncogene receptor tyrosine kinase activity.

PATIENTS AND METHODS

From this two-part phase I, multicenter study, pexidartinib, a small-molecule tyrosine kinase inhibitor that targets CSF1R, KIT, and FMS-like tyrosine kinase 3 (FLT3), was evaluated in six adult patient cohorts (part 2, extension) with advanced solid tumors associated with dysregulated CSF1R. Adverse events, pharmacokinetics, and tumor responses were assessed for all patients; patients with tenosynovial giant cell tumor (TGCT) were also evaluated for tumor volume score (TVS) and patient-reported outcomes (PRO). CSF1 transcripts and gene expression were explored in TGCT biopsies.

RESULTS

Ninety-one patients were treated: TGCT patients (n = 39) had a median treatment duration of 511 days, while other solid tumor patients (n = 52) had a median treatment duration of 56 days. TGCT patients had response rates of 62% (RECIST 1.1) and 56% (TVS) for the full analysis set. PRO assessments for pain showed improvement in patient symptoms, and 76% (19/25) of TGCT tissue biopsy specimens showed evidence of abnormal CSF1 transcripts. Pexidartinib treatment of TGCT resulted in tumor regression and symptomatic benefit in most patients. Pexidartinib toxicity was manageable over the entire study.

CONCLUSIONS

These results offer insight into outcome patterns in cancers whose biology suggests use of a CSF1R inhibitor. Pexidartinib results in tumor regression in TGCT patients, providing prolonged control with an acceptable safety profile.

Is intra-articular infliximab therapy a good alternative to radionuclide synovectomy for a patient with refractory pigmented villonodular synovitis?

Pigmented villonodular synovitis (PVNS) is a rare disease that has clinical and histopathological characteristics of both benign proliferative disorder and a chronic inflammatory process of the synovial tissue. The primary mode of treatment is surgery followed by an adjuvant radiotherapy; however, the risk of recurrence is a significant (40–70%). Several publications suggest that the TNF-α inhibitors might be a treatment option. We present a case of a 29-year-old female diagnosed with PVNS of the knee joint, refractory to surgery and 3 radionuclide synovectomies. Because the possibilities of conventional therapy were exhausted, treatment with an intra-articular anti-TNF-α monoclonal antibody (infliximab) was performed. Despite a high safety profile and a good tolerance of that therapy we did not observe significant clinical and radiological improvement. To assess the effectiveness of intra-articular TNF-α inhibitors as an adjuvant treatment in PVNS, prospective studies are needed.

Clinical evaluation of colony-stimulating factor 1 receptor inhibitors

Signaling through colony-stimulating factor 1 receptor (CSF1R) regulates the development, differentiation, and activation of mononuclear phagocytic cells. Inhibition of this pathway provides an opportunity for therapeutic intervention in diseases in which these cells play a pathogenic role, including cancers, inflammation, fibrosis, and others. Multiple monoclonal antibodies and small molecule inhibitors targeting CSF1R or its known ligands CSF1 and IL-34 have been clinically tested and are generally well tolerated with side effects associated with on-target macrophage inhibition or depletion. To date, clinical activity of CSF1R inhibitors has been primarily observed in diffuse-type tenosynovial giant cell tumors, a disease characterized by genetic alterations in CSF1 leading to dysregulated CSF1R signaling. Expanded development into novel indications such as chronic graft vs host disease may provide new opportunities to further explore areas where a role for CSF1R dependent monocytes and macrophages has been established. This review presents key findings from the clinical development of 12 CSF1/CSF1R targeted therapies as monotherapy or in combination with immune checkpoint inhibitors and chemotherapy.

Evaluation of anti-EGFR potential of quinazoline derivatives using molecular docking: An in silico approach

Overexpression of epidermal growth factor receptor (EGFR) is commonly reported in epithelial malignancies such as oral squamous cell carcinoma. Inhibition of EGFR is, therefore, considered a potential therapeutic strategy. Among various anti-EGFR drugs, quinazoline-based tyrosine kinase inhibitors (TKIs) have gained increasing attention. Present study focused to investigate anti-EGFR potential of quinazoline-based compounds using in silico approach. Two widely used docking programs GOLD and AutoDock Vina were used for the study. Four drugs were docked on the X-ray crystallographic EGFR structure (1XKK). GOLD and AutoDock Vina produced results in terms of fitness score and binding affinity, respectively. GOLD prioritized varlitinib and AutoDock Vina preferred imatinib over other drugs. To reach the consensus from both software, all four drugs coupled with EGFR were studied rigorously. GOLD demonstrated varlitinib to be the best inhibitor with highest fitness score of 109, whereas AutoDock Vina revealed imatinib as the potent ligand with least binding energy of -10.9 kcal/mol. Most stable hydrogen bonds observed by GOLD and maximum number of hydrophobic contacts along with strong ionic interaction exhibited by varlitinib through both software have led us to conclude varlitinib as the most potent EGFR inhibitor in the studied group.

The diffuse-type tenosynovial giant cell tumor (dt-TGCT) patient journey: a prospective multicenter study

Background

Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive neoplasm arising from the synovium of joints, bursae, and tendon sheaths affecting small and large joints. It represents a wide spectrum ranging from minimally symptomatic to massively debilitating. Most findings to date are mainly from small, retrospective case series, and thus the morbidity and actual impact of this rare disease remain to be elucidated. This study prospectively explores the management of TGCT in tertiary sarcoma centers.

Methods

The TGCT Observational Platform Project registry was a multinational, multicenter, prospective observational study involving 12 tertiary sarcoma centers in 7 European countries, and 2 US sites. This study enrolled for 2 years all consecutive ≥ 18 years old patients, with histologically diagnosed primary or recurrent cases of diffuse-type TGCT. Patient demographic and clinical characteristics were collected at baseline and every 6 months for 24 months. Quality of life questionnaires (PROMIS-PF and EQ-5D) were also administered at the same time-points. Here we report baseline patient characteristics.

Results

166 patients were enrolled between November 2016 and March 2019. Baseline characteristics were: mean age 44 years (mean age at disease onset: 39 years), 139/166 (83.7%) had prior treatment, 71/166 patients (42.8%) had ≥ 1 recurrence after treatment of their primary tumor, 76/136 (55.9%) visited a medical specialist ≥ 5 times, 66/116 (56.9%) missed work in the 24 months prior to baseline, and 17/166 (11.6%) changed employment status or retired prematurely due to disease burden. Prior treatment consisted of surgery (i.e., arthroscopic, open synovectomy) (128/166; 77.1%) and systemic treatments (52/166; 31.3%) with imatinib (19/52; 36.5%) or pexidartinib (27/52; 51.9%). Treatment strategies at baseline visits consisted mainly of watchful waiting (81/166; 48.8%), surgery (41/166; 24.7%), or targeted systemic therapy (37/166; 22.3%). Patients indicated for treatment reported more impairment compared to patients indicated for watchful waiting: worst stiffness NRS 5.16/3.44, worst pain NRS 6.13/5.03, PROMIS-PF 39.48/43.85, and EQ-5D VAS 66.54/71.85.

Conclusion

This study confirms that diffuse-type TGCT can highly impact quality of life. A prospective observational registry in rare disease is feasible and can be a tool to collect curated-population reflective data in orphan diseases.

Name of registry: Tenosynovial Giant Cell Tumors (TGCT) Observational Platform Project (TOPP).

Trial registration number: NCT02948088.

Date of registration: 10 October 2016.

URL of Trial registry record: https://clinicaltrials.gov/ct2/show/NCT02948088?term=NCT02948088&draw=2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01820-6.

Management of tenosynovial giant cell tumour of the foot and ankle

AIMS

Tenosynovial giant cell tumour (TGCT) is one of the most common soft-tissue tumours of the foot and ankle and can behave in a locally aggressive manner. Tumour control can be difficult, despite the various methods of treatment available. Since treatment guidelines are lacking, the aim of this study was to review the multidisciplinary management by presenting the largest series of TGCT of the foot and ankle to date from two specialized sarcoma centres.

METHODS

The Oxford Tumour Registry and the Leiden University Medical Centre Sarcoma Registry were retrospectively reviewed for patients with histologically proven foot and ankle TGCT diagnosed between January 2002 and August 2019.

RESULTS

A total of 84 patients were included. There were 39 men and 45 women with a mean age at primary treatment of 38.3 years (9 to 72). The median follow-up was 46.5 months (interquartile range (IQR) 21.3 to 82.3). Localized-type TGCT (n = 15) predominantly affected forefoot, whereas diffuse-type TGCT (Dt-TGCT) (n = 9) tended to panarticular involvement. TGCT was not included in the radiological differential diagnosis in 20% (n = 15/75). Most patients had open rather than arthroscopic surgery (76 vs 17). The highest recurrence rates were seen with Dt-TGCT (61%; n = 23/38), panarticular involvement (83%; n = 5/8), and after arthroscopy (47%; n = 8/17). Three (4%) fusions were carried out for osteochondral destruction by Dt-TGCT. There were 14 (16%) patients with Dt-TGCT who underwent systemic treatment, mostly in refractory cases (79%; n = 11). TGCT initially decreased or stabilized in 12 patients (86%), but progressed in five (36%) during follow-up; all five underwent subsequent surgery. Side effects were reported in 12 patients (86%).

CONCLUSION

We recommend open surgical excision as the primary treatment for TGCT of the foot and ankle, particularly in patients with Dt-TGCT with extra-articular involvement. Severe osteochondral destruction may justify salvage procedures, although these are not often undertaken. Systemic treatment is indicated for unresectable or refractory cases. However, side effects are commonly experienced, and relapses may occur once treatment has ceased. Cite this article: Bone Joint J 2021;103-B(4):788-794.

Pexidartinib Long-Term Hepatic Safety Profile in Patients with Tenosynovial Giant Cell Tumors

Background

Pexidartinib is approved in the U.S. for tenosynovial giant cell tumors (TGCTs). Herein, we assessed the hepatic safety profile of pexidartinib across patients with TGCTs receiving pexidartinib.

Materials, and Methods

Hepatic adverse reactions (ARs) were assessed by type and magnitude of liver test abnormalities, classified as (a) isolated aminotransferase elevations (alanine [ALT] or aspartate [AST], without significant alkaline phosphatase [ALP] or bilirubin elevations), or (b) mixed or cholestatic hepatotoxicity (increase in ALP with or without ALT/AST and bilirubin elevations, based on adjudication). Median follow‐up from initial pexidartinib treatment was 39 months (range, 32–82) in 140 patients with TGCTs across clinical studies NCT01004861, NCT02371369, NCT02734433, and NCT03291288.

Results

In total, 95% of patients with TGCTs (133/140) treated with pexidartinib (median duration of exposure, 19 months [range, 1–76]), experienced a hepatic AR. A total of 128 patients (91%) had reversible, low‐grade dose‐dependent isolated AST/ALT elevations without significant ALP elevations. Five patients (4%) experienced serious mixed or cholestatic injury. No case met Hy's law criteria. Onset of hepatic ARs was predominantly in the first 2 months. All five serious hepatic AR cases recovered 1–7 months following pexidartinib discontinuation. Five patients from the non‐TGCT population (N = 658) experienced serious hepatic ARs, two irreversible cases.

Conclusion

This pooled analysis provides information to help form the basis for the treating physician's risk assessment for patients with TCGTs, a locally aggressive but typically nonmetastatic tumor. In particular, long‐term treatment with pexidartinib has a predictable effect on hepatic aminotransferases and unpredictable risk of serious cholestatic or mixed liver injury.

Implications for Practice

This is the first long‐term pooled analysis to report on the long‐term hepatic safety of pexidartinib in patients with tenosynovial giant cell tumors associated with severe morbidity or functional limitations and not amenable to improvement with surgery. These findings extend beyond what has been previously published, describing the observed instances of hepatic toxicity following pexidartinib treatment across the clinical development program. This information is highly relevant for medical oncologists and orthopedic oncologists and provides guidance for its proper use for appropriate patients within the Pexidartinib Risk Evaluation and Mitigation Safety program.

Pexidartinib is approved in the U.S. for treatment of tenosynovial giant cell tumors (TGCT). This article assesses the hepatic safety profile of pexidartinib in TGCT cases and describes risk mitigation procedures designed to identify any instances of serious liver injury as early as possible to better inform prescribers and patients about this drug.

Long-term outcomes of pexidartinib in tenosynovial giant cell tumors

Background

The objective of this study was to report on the long‐term effects of pexidartinib on tenosynovial giant cell tumor (TGCT).

Methods

This was a pooled analysis encompassing 3 pexidartinib‐treated TGCT cohorts: 1) a phase 1 extension study (NCT01004861; 1000 mg/d; n = 39), 2) ENLIVEN patients randomized to pexidartinib (1000 mg/d for 2 weeks and then 800 mg/d; n = 61), and 3) ENLIVEN crossover patients (NCT02371369; 800 mg/d; n = 30). Eligible patients were 18 years old or older and had a histologically confirmed TGCT that was unresectable and symptomatic. Efficacy endpoints included the best overall response (complete or partial response) and the duration of response (DOR) by the Response Evaluation Criteria in Solid Tumors (RECIST) and the tumor volume score (TVS). The safety assessment included the frequency of treatment‐emergent adverse events (TEAEs) and hepatic laboratory abnormalities (aminotransferase elevations and mixed/cholestatic hepatotoxicity). The data cutoff was May 31, 2019.

Results

One hundred thirty patients with TGCT received pexidartinib (median treatment duration, 19 months; range, 1 to 76+ months); 54 (42%) remained on treatment at the end of the analysis (26 months after initial data cut of March 2017). The RECIST overall response rate (ORR) was 60%; the TVS ORR was 65%. The median times to response were 3.4 (RECIST) and 2.8 months (TVS), with 48 of the responding patients (62%) achieving a RECIST partial response by 6 months and with 72 (92%) doing so by 18 months. The median DOR was reached for TVS (46.8 months). Reported TEAEs were mostly low‐grade, with hair color changes being most frequent (75%). Most liver abnormalities (92%) were aminotransferase elevations; 4 patients (3%) experienced mixed/cholestatic hepatotoxicity (all within the first 2 months of treatment), which was reversible in all cases (recovery spanned 1‐7 months).

Conclusions

This study demonstrates the prolonged efficacy and tolerability of long‐term pexidartinib treatment for TGCT.

This analysis further illustrates that systemic therapy targeting the CSF1/CSF1R pathway is an effective therapeutic strategy in patients with tenosynovial giant cell tumor. Because of the limited availability of long‐term prospective data for tenosynovial giant cell tumor, these findings are encouraging and demonstrate the overall long‐term benefit of continued treatment with pexidartinib.

Management of Tenosynovial Giant Cell Tumor: A Neoplastic and Inflammatory Disease

Background:

Patients with diffuse tenosynovial giant cell tumor (TGCT) face a high risk of recurrence, progression, and disability. This systematic review assesses the recent evidence of surgical, adjuvant, and systemic treatments for TGCT.

Methods:

We searched PubMed and Ovid with the terms “Giant cell tumor of tendon sheath” OR “pigmented villonodular synovitis” OR “tenosynovial giant cell” AND “treatment” OR “surgery.” Inclusion criteria: published 2013 to present; prospective or retrospective design; English language; > 20 patients with histopathological confirmed diagnosis of TGCT; and ≥ 1 efficacy and/or safety outcome from surgery, systemic drug therapy, or adjuvant ⁹⁰yttrium radiosynoviorthesis.

Results:

Of the 434 studies identified, 25 met the inclusion criteria. Of 11 studies in patients with disease in the knee, nine examined surgical treatment approaches, and two evaluated adjuvant ⁹⁰yttrium radiosynoviorthesis. Of 11 studies in patients with mixed sites of disease, six assessed surgical treatment approaches, and five evaluated systemic drug therapies. Three studies assessed surgery in patients with TGCT in the hand, hip, and ankle or foot.

Discussion:

The high rates of recurrence and risks associated with surgery emphasize the need for novel treatments in patients with symptomatic, advanced TGCT. Systemic therapy may be valuable as part of a multidisciplinary approach.

The effect of Imatinib Mesylate in diffuse-type Tenosynovial Giant Cell Tumours on MR imaging and PET-CT

INTRODUCTION

Recurrence rates remain high after surgical treatment of diffuse-type Tenosynovial Giant Cell Tumour (TGCT). Imatinib Mesylate (IM) blocks Colony Stimulating Factor1 Receptor (CSF1R), the driver mechanism in TGCT. The aim of this study was to determine if IM reduces the tumour metabolic activity evaluated by PET-CT and to compare this response with the response seen on MR imaging.

MATERIALS AND METHODS

25 Consecutive patients treated with IM (off label use) for locally advanced (N = 12) or recurrent (N = 13) diffuse-type TGCT were included, 15 male and median age at diagnosis 39 (IQR 31-47) years. The knee was most frequently affected (n = 16; 64%). The effect of IM was assessed pre- and post-IM treatment by comparing MR scans and PET-CT. MR scans were assessed by Tumour Volume Score (TVS), an estimation of the tumour volume as a percentage of the total synovial cavity. PET-CT scans were evaluated based on maximum standardized uptake value (SUV-max). Partial response was defined as more than 50% tumour reduction with TVS and a decrease of at least 30% on SUV-max.

RESULTS

Median duration of IM treatment was 7.0 (IQR 4.2-11.5) months. Twenty patients (80%) discontinued IM treatment for poor response or intended surgery. Twenty patients experienced an adverse event grade 1-2, three patients grade 3 (creatinine increment, neutropenic sepsis, liver dysfunction). MR assessment of all joints showed 32% (6/19) partial response and 63% (12/19) stable disease, with a mean difference of 12% (P = 0.467; CI -22.4-46.0) TVS between pre- and post-IM and a significant mean difference of 23% (P = 0.021; CI 4.2-21.6) in all knee lesions. PET-CT, all joints, showed a significantly decreased mean difference of 5.3 (P = 0.004; CI 1.9-8.7) SUV-max between pre- and post-IM treatment (58% (11/19) partial response, 37% (7/19) stable disease). No correlation between MR imaging and PET-CT could be appreciated in 15 patients with complete radiological data.

CONCLUSION

This study confirms the moderate radiological response of IM in diffuse-type TGCT. PET-CT is a valuable additional diagnostic tool to quantify response to tyrosine kinase inhibitor treatment. Its value should be assessed further to validate its efficacy in the objective measurement of biological response in targeted systemic treatment of TGCT.

Pexidartinib for the treatment of adult symptomatic patients with tenosynovial giant cell tumors

INTRODUCTION

Tenosynovial giant cell tumor (TGCT) is a benign mesenchymal tumor arising from the synovium of tendon sheats and joints, driven by colony-stimulating factor 1 (CSF1) over-expression. Standard treatment is surgery, but local recurrences are frequent, especially in diffuse TGCT subtype, rarely cured with surgery. When TGCT becomes a chronic condition, which may severely compromise joint function and quality of life, patients may need a systemic therapy. Areas covered: We reviewed the drugs on clinical development in TGCT, focusing on the pharmacodynamics, pharmacokinetics, efficacy, and toxicity profile of pexidartinib, the first drug approved in the US for TGCT, and on the open questions about its optimal use in clinical practice.

EXPERT OPINION

CSFR1 inhibitors have opened a new avenue for treatment of TGCT patients. Pexidartinib is the first-in-class FDA approved agent for symptomatic locally advanced TGCT, based on a phase III study where pexidartinib showed high anti-tumor activity, improved patient symptoms, and functional outcome. A few cases of potentially life-threatening hepatic toxicity were observed. TGCT patients candidate to pexidartinib need to be carefully selected by the multidisciplinary board of center of expertise, balancing the expected risk-benefit ratio. Close monitoring of liver function and adequate education on the approved indication is warranted.