IDH mutations in G2-3 conventional central bone chondrosarcoma: a mono institutional experience.

BACKGROUND: Heterozygous isocitrate dehydrogenase (IDH) mutations occur in about half of conventional central bone chondrosarcomas (CCBC). Aim of this study was to assess the frequency and prognostic impact of IDH mutations in high grade CCBC patients. METHODS: 64 patients with G2 and G3 CCBC were included. DNA extraction, PCR amplification of IDH1/2 exon 4s, and sequencing analysis with Sanger were performed. RESULTS: IDH mutations were detected in 24/54 patients (44%): IDH1 in 18, IDH2 in 4, and both IDH1/2 in 2 patients. The frequency of mutations was 37% in G2 vs. 69% in G3 (p = 0.039), and 100% in three Ollier disease associated chondrosarcoma. 5-year overall survival (OS) at 124 months (range 1-166) was 51%, with no significant difference based on the IDH mutational status: 61% in IDHmut vs. 44% in IDH wild type (IDHwt). The 5-year relapse free survival (RFS) was 33% (95% CI:10-57) for IDHmut vs. 57% (95%CI: 30-77) for IDHwt. Progression free survival (PFS) was 25% (95%CI:1-65) IDHmut vs. 16% (95%CI: 0.7-52) IDHwt. 55% (5/9) of IDHmut G2 became higher grade at the recurrence, as compared with 25% (3/12) of G2 IDHwt. CONCLUSIONS: This study shows a higher frequency of IDH mutations in G3 CCBC as compared with G2. No significant differences in OS, RFS, and PFS by mutational status were detected. After relapse, a higher rate of G3 for IDH mutated CCBC was observed.

Irinotecan and temozolomide in recurrent Ewing sarcoma: an analysis in 51 adult and pediatric patients.

BACKGROUND: Data on temozolomide (TEM) and irinotecan (IRI) activity in recurrent Ewing sarcoma (EWS), especially in adult patients, are limited. METHODS: Patients receiving TEM 100 mg/m2/day oral, and IRI 40 mg/m2/day intravenous, days 1-5, every 21 days, were included in this multi-institutional retrospective study. Disease control rate (DCR) [overall response rate (ORR) [complete response (CR) + partial response (PR)] + stable disease (SD)], 6-months progression-free survival (6-mos PFS) and 1-year overall survival (OS) were assessed. RESULTS: The median age of the 51 patients was 21 years (range 3-65 years): 34 patients (66%) were adults (≥18 years of age), 24 (48%) had ECOG 1 and 35 (69%) were presented with multiple site recurrence. TEMIRI was used at first relapse/progression in 13 (25%) patients, while the remainder received TEMIRI for second or greater relapse/progression. Fourteen (27%) patients had received prior myeloablative therapy with busulfan and melphalan. We observed five (10%) CR, 12 (24%) PR and 19 (37%) SD, with a DCR of 71%. 6-mos PFS was 49% (95% CI 35-63) and it was significantly influenced by ECOG (6-mos PFS 64% [95% CI 45-83] for ECOG 0, 34% [95% CI 14-54] for ECOG ≥1; p = .006) and LDH (6-mos PFS 62% [95% CI 44-79] for normal LDH, 22% [95% CI 3-42] for high LDH; p = .02), with no difference according to line of treatment, age and metastatic pattern. One-year OS was 55% (95% CI 39-70), with RECIST response (p = .001) and ECOG (p = .0002) independently associated with outcome. Grade 3 and 4 toxicity included neutropenia in 12% of patients, thrombocytopenia in 4%, diarrhea in 4%. CONCLUSIONS: This series confirms the activity of TEMIRI in both adults and pediatric patients. This schedule offers a 71% DCR, independently of the line of chemotherapy. Predictive factors of response are ECOG and LDH.

Gemcitabine and docetaxel in relapsed and unresectable high-grade osteosarcoma and spindle cell sarcoma of bone.

BACKGROUND: Few new compounds are available for relapsed osteosarcoma. We retrospectively evaluated the activity of gemcitabine (G) plus docetaxel (D) in patients with relapsed high-grade osteosarcoma and high-grade spindle cell sarcoma of bone (HGS). METHODS: Patients receiving G 900 mg/m(2) d 1, 8; D 75 mg/m(2) d 8, every 21 days were eligible. Primary end-point: progression-free survival (PFS) at 4 months; secondary end-point: overall survival (OS) and response rate. RESULTS: Fifty-one patients were included, with a median age of 17 years (8-71), 26 (51%) were pediatric patients. GD line of treatment: 2nd in 14 patients, ≥3rd in 37. 25 (49%) patients had metastases limited to lungs, 26 (51%) multiple sites. HISTOLOGY: 40 (78%) osteosarcoma, 11 (22%) HGS. Eight (16%) patients achieved surgical complete response (sCR2) after GD. Four-month PFS rate was 46%, and significantly better for patients with ECOG 0 (ECOG 0: 54% vs ECOG 1: 43% vs ECOG 2: 0%; p = 0.003), for patients undergoing metastasectomy after GD (sCR2 75% vs no-sCR2 40 %, p = 0.02) and for osteosarcoma (osteosarcoma 56% vs HGS 18%; p = 0.05), with no differences according to age, line of treatment, and pattern of metastases. Forty-six cases had RECIST measurable disease: 6 (13%) patients had a partial response (PR), 20 (43%) had stable disease (SD) and 20 (43%) had progressive disease (PD). The 1-year OS was 30%: 67% for PR, 54% for SD and 20% for PD (p = 0.005). CONCLUSIONS: GD is an active treatment for relapsed high-grade osteosarcoma, especially for ECOG 0 patients, and should be included in the therapeutic armamentarium of metastatic osteosarcoma.

S-p-bromobenzyl-glutathione cyclopentyl diester (BBGC) as novel therapeutic strategy to enhance trabectedin anti-tumor effect in soft tissue sarcoma preclinical models.

Trabectedin, approved for the treatment of soft tissue sarcoma (STS), interferes with cell division and genetic transcription processes. Due to its strong anti-tumor activity in only certain histotypes, several studies on trabectedin combinations are currently ongoing to improve its efficacy. In this study, we aimed to investigate novel potential therapeutic strategies to enhance the anti-tumor effect of trabectedin using integrated in silico, in vitro, and in vivo approaches. For in silico analysis, we screened two public datasets, GSEA M5190 and TCGA SARC. Fibrosarcoma, leiomyosarcoma, dedifferentiated, and myxoid liposarcoma cell lines were used for in vitro studies. For in vivo experiments, fibrosarcoma orthotopic murine model was developed. In silico analysis identified Glo1 as the only druggable target upregulated after trabectedin treatment and correlated with poor prognosis. The specific Glo1 inhibitor, S-p-bromobenzylglutathione cyclopentyl diester (BBGC), increased trabectedin cytotoxicity in STS cells, and restored drug sensitivity in myxoid liposarcoma cells resistant to trabectedin. Moreover, the combined treatment with BBGC and trabectedin had a synergistic antitumor effect in vivo without any additional toxicity to mice. Based on these results, we believe that BBGC warrants further investigation to evaluate its potential clinical use in combination with trabectedin.

Low-grade fibromyxoid sarcoma and sclerosing epithelioid fibrosarcoma, outcome of advanced disease: retrospective study from the Ultra-Rare Sarcoma Working Group.

BACKGROUND: To present findings from a retrospective study conducted by the Ultra-Rare Sarcoma Working Group on metastatic low-grade fibromyxoid sarcoma (LGFMS), sclerosing epithelioid fibrosarcoma (SEF), and hybrid (H)-LGFMS/SEF across 28 global centres. METHODS: Patients treated at participating institutions from January 2000 to September 2022 were retrospectively selected. Diagnosis was confirmed by expert pathologists. Primary endpoint was progression-free survival (PFS-1) from metastasis detection to first progression or death. PFS-2 was calculated from therapy initiation. RESULTS: A total of 101 patients were identified (32 LGFMS, 50 SEF, 19 H-LGFMS/SEF). Median (m) follow-up was 62.1 months. mPFS-1 was 28.7, 11.8, and 20.3 months for LGFMS, SEF, and H-LGFMS/SEF, respectively. mOS was 145.8, 41.9, and 113.5 months, respectively. Treatments included anthracycline-based chemotherapy, gemcitabine-based chemotherapy (G), pazopanib, trabectedin, others. mPFS-2 was: 20.1, 5.5, and 3.5 months in H-LGFMS/SEF, SEF, and LGFMS, respectively, with anthracyclines; 19.5, 7.7, and 6.9 months in LGFMS, SEF, and H-LGFMS/SEF, respectively, with pazopanib; 12.0, 9.7, and 3.1 months in H-LGFMS/SEF, LGFMS, and SEF, respectively. Occasional responses occurred with ifosfamide/oral cyclophosphamide, and prolonged stable disease with immune checkpoint inhibitors. CONCLUSIONS: In this series, the largest available, metastatic LGFMS, SEF, and H-LGFMS/SEF showed different courses. Systemic agents have modest efficacy, informing future trials of novel agents for these tumours.

Phase II study on lapatinib in advanced EGFR-positive chordoma.

BACKGROUND: To report on a prospective, investigator-driven, phase II study on lapatinib in epidermal growth factor receptor (EGFR)-positive advanced chordoma patients. PATIENTS AND METHODS: From December 2009 to January 2012, 18 advanced progressing chordoma patients entered this study (median age: 61 years; disease extent: metastatic 72% and locally advanced 28%). Epidermal growth factor receptor (EGFR) expression and activation were evaluated by immunohistochemistry and/or phospho-arrays, real-time polimerase chain reaction, fluorescence immunostaining. Fluorescence in situ hybridization analysis was also carried out. Patients received lapatinib 1500 mg/day (mean dose intensity = 1282 mg/day), until progression or toxicity. The primary study end point was response rate (RR) as per Choi criteria. Secondary end points were RR by Response Evaluation Criteria in Solid Tumor (RECIST), overall survival, progression-free survival (PFS) and clinical benefit rate (CBR; RECIST complete response + partial response (PR) + stable disease (SD) ≥ 6 months). RESULTS: All patients were evaluable for response. Six (33.3%) patients had PR and 7 (38.9%) SD, as their best Choi responses, corresponding to RECIST SD in all cases. Median PFS by Choi was 6 [interquartile (IQ) range 3-8] months. Median PFS by RECIST was 8 (IQ range 4-12) months, with a 22% CBR. CONCLUSIONS: This phase II study showed a modest antitumor activity of lapatinib in chordoma. The clinical exploitation of EGFR targeting in chordoma needs to be further investigated, both clinically and preclinically. Clinical trial Registration No: EU Clinical Trials Register trial no. 2009-014456-29.

Advanced chondrosarcomas: role of chemotherapy and survival.

BACKGROUND: There are limited data about the role of chemotherapy in patients with advanced chondrosarcomas. METHODS: The medical charts of 180 patients with advanced chondrosarcomas having received chemotherapy in 15 participating institutions between 1988 and 2011 were reviewed. RESULTS: Median age was 52 years. Sixty-three percent of patients had conventional chondrosarcoma and 88% had metastatic disease. Combination chemotherapy was delivered in 98 cases (54.5%). One hundred and thirty-one patients (73%) received an anthracycline-containing regimen. Using RECIST, the objective response rate was significantly different according to histological subtype, being 31% for mesenchymal chondrosarcoma, 20.5% for dedifferentiated chondrosarcoma, 11.5% for conventional chondrosarcoma and 0% for clear-cell chondrosarcoma (P = 0.04). Median progression-free survival (PFS) was 4.7 months [95% confidence interval (CI) 3-6.5]. Performance status (PS) ≥2, number of metastatic sites ≥1 and single-agent regimen were independently associated with poor PFS. Median overall survival (OS) was 18 months (95% CI 14.5-21.6). PS, number of metastatic sites and palliative surgery were independently associated with OS. CONCLUSIONS: Conventional chemotherapy have very limited efficacy in patients with advanced chondrosarcoma, the highest benefit being observed in mesenchymal and dedifferentiated chondrosarcoma. These data should be used as a reference for response and outcome in the assessment of investigational drugs in advanced chondrosarcoma.

Palliative embolisation for advanced bone sarcomas.

PURPOSE: Managing patients with advanced bone sarcomas - namely, recurrent, unresectable and metastatic - is mostly aimed at palliation. The role of embolisation for pain relief for these patients has not been previously reported. We therefore performed this study to emphasise the palliative role of embolisation for pain relief of advanced bone sarcoma patients. MATERIALS AND METHODS: We retrospectively studied 43 patients with advanced bone sarcomas treated with palliative embolisation with N-2-butyl-cyanoacrylate from 2004 to 2011. All patients had primary treatments including chemotherapy, radiation therapy, radiofrequency thermal ablation, and/or surgery for their advanced sarcomas and were referred for embolisation as end-stage treatment for continuous severe local pain. The effect of embolisation was evaluated with a pain score scale and analgesic use. Mean follow-up was 7 (range, 1-19) months); all patients were dead at the last follow-up. RESULTS: In all patients, angiography showed increased pathological vascularisation of the sarcomas; three to six feeding vessels were embolised in each procedure. Almost complete pain relief and >50% reduction in analgesic use was experienced by 36 patients with highly hypervascular sarcomas and sarcomas in the pelvis and shoulder girdle. Moderate pain relief and 50% reduction in analgesic use was experienced by seven patients with spinal and sacral lesions. Within the available follow-up, no patient had recurrent pain with the same intensity as before embolisation. All patients experienced ischaemic pain at the site of embolisation that resolved completely with analgesics. Six patients with advanced pelvic bone sarcomas experienced paraesthesias at the distribution of the sciatic nerve that resolved completely with methylprednisolone. CONCLUSIONS: Embolisation is a safe and effective local palliative treatment for patients with advanced sarcomas, providing optimum pain relief with the least discomfort and the possibility of minor complications only.

A phase II trial of sorafenib in relapsed and unresectable high-grade osteosarcoma after failure of standard multimodal therapy: an Italian Sarcoma Group study.

PURPOSE: After standard multimodal therapy, the prognosis of relapsed and unresectable high-grade osteosarcoma is dismal and unchanged over the last decades. Recently, mitogen-activated protein kinases were shown to be activated in osteosarcoma specimens, suggesting, therefore, they are suitable targets for the multikinase inhibitor sorafenib. Thus, we explored sorafenib activity in patients with relapsed and unresectable osteosarcoma. EXPERIMENTAL DESIGN: Patients > 14 years, progressing after standard treatment, were eligible to receive 400 mg of sorafenib twice daily until progression or unacceptable toxicity. The primary end point was progression-free survival (PFS) at 4 months. Secondary objectives were PFS, overall survival (OS), clinical benefit rate (CBR), defined as no progression at 6 months and safety. This nonrandomized phase II study used a Simon two-stage design. PFS and OS at 95% confidence intervals (95% CIs) were calculated by the Kaplan-Meier method. All tests were two sided. RESULTS: Thirty-five patients were enrolled. PFS at 4 months was 46% (95% CI 28% to 63%). Median PFS and OS were 4 (95% CI 2-5) and 7 (95% CI 7-8) months, respectively. The CBR was 29% (95% CI 13% to 44%). We observed 3 (8%) partial responses (PRs), 2 (6%) minor responses (< 30% tumor shrinkage) and 12 (34%) stable diseases (SDs). For six patients (17%), PR/SD lasted ≥ 6 months. Noteworthy, tumor density reduction and [(18)F]2-fluoro-2-deoxy-d-glucose-positron emission tomography responses were observed among SD patients. Sorafenib was reduced or briefly interrupted in 16 (46%) patients and permanently discontinued in one (3%) case due to toxicity. CONCLUSIONS: Sorafenib demonstrated activity as a second- or third-line treatment in terms of PFS at 4 months with some unprecedented long-lasting responses. Sorafenib, the first targeted therapy showing activity in osteosarcoma patients, deserves further investigations.

Palliative treatments for advanced osteosarcoma.

Advances in diagnostic imaging, interventional radiology, chemotherapy and surgery greatly improved the outcome of patients with osteosarcoma, and made limb salvage possible without compromising survival. In these patients, the prognosis is influenced by the site and resectability of the tumor, prior malignancy, and histological response to preoperative chemotherapy. Unfortunately, the progress has not been as significant in the treatment of advanced osteosarcoma, namely metastatic, recurrent and unresectable tumor. Yet, although advanced and forecasting a dismal prognosis, advanced osteosarcoma is not necessarily untreatable. Aggressive local and medical treatments, including surgical removal of primary and/or metastatic disease are currently available; however, yet, most treatments aim at palliation. Palliative local treatments including isolated limb perfusion, radiation therapy, embolization, chemoembolization, thermal ablation and cryoablation, all have an important role for these patients. The aim of palliative treatments is to achieve a mild response by offering the least discomfort to the patient with the minimum possible complications, and possibly increase of survival.

SELNET clinical practice guidelines for bone sarcoma.

Bone sarcoma are infrequent diseases, representing < 0.2% of all adult neoplasms. A multidisciplinary management within reference centers for sarcoma, with discussion of the diagnostic and therapeutic strategies within an expert multidisciplinary tumour board, is essential for these patients, given its heterogeneity and low frequency. This approach leads to an improvement in patient's outcome, as demonstrated in several studies. The Sarcoma European Latin-American Network (SELNET), aims to improve clinical outcome in sarcoma care, with a special focus in Latin-American countries. These Clinical Practice Guidelines (CPG) have been developed and agreed by a multidisciplinary expert group (including medical and radiation oncologist, surgical oncologist, orthopaedic surgeons, radiologist, pathologist, molecular biologist and representatives of patients advocacy groups) of the SELNET consortium, and are conceived to provide the standard approach to diagnosis, treatment and follow-up of bone sarcoma patients in the Latin-American context.

New onset of electrocardiographic abnormalities heralding hypertrophic cardiomyopathy in an adult athlete.

A 41-year-old male asymptomatic athlete with unremarkable personal and family history of heart disease underwent annual preparticipation screening. No abnormalities were noted on prior testing. On this occasion, a 12-lead electrocardiogram showed diffused and marked repolarization abnormalities. He was therefore referred for echocardiography, which showed moderate asymmetric hypertrophy localized at the mid-apical portions of the left ventricular anterolateral wall. Cardiac magnetic resonance confirmed the diagnosis of hypertrophic cardiomyopathy. Re-evaluation of the electrocardiogram performed the previous year revealed a completely normal tracing.

Economic burden and health-related quality of life in tenosynovial giant-cell tumour patients in Europe: an observational disease registry.

BACKGROUND: Tenosynovial Giant-Cell Tumour (TGCT) is a benign clonal neoplastic proliferation arising from the synovium, causing a variety of symptoms and often requiring repetitive surgery. This study aims to define the economic burden-from a societal perspective-associated with TGCT patients and their health-related quality of life (HRQOL) in six European countries. METHODS: This article analyses data from a multinational, multicentre, prospective observational registry, the TGCT Observational Platform Project (TOPP), involving hospitals and tertiary sarcoma centres from six European countries (Austria, France, Germany, Italy, the Netherlands, and Spain). It includes information on TGCT patients' health-related quality of life and healthcare and non-healthcare resources used at baseline (the 12-month period prior to the patients entering the registry) and after 12 months of follow-up. RESULTS: 146 TGCT patients enrolled for the study, of which 137 fulfilled the inclusion criteria. Their mean age was 44.5 years, and 62% were female. The annual average total costs associated with TGCT were €4866 at baseline and €5160 at the 12-month follow-up visit. The annual average healthcare costs associated with TGCT were €4620 at baseline, of which 67% and 18% corresponded to surgery and medical visits, respectively. At the 12-month follow-up, the mean healthcare costs amounted to €5094, with surgery representing 70% of total costs. Loss of productivity represented, on average, 5% of the total cost at baseline and 1.3% at follow-up. The most-affected HRQOL dimensions, measured with the EQ-5D-5L instrument, were pain or discomfort, mobility, and the performance of usual activities, both at baseline and at the follow-up visit. Regarding HRQOL, patients declared a mean index score of 0.75 at baseline and 0.76 at the 12-month follow-up. CONCLUSION: The results suggest that TGCT places a heavy burden on its sufferers, which increases after one year of follow-up, mainly due to the healthcare resources required-in particular, surgical procedures. As a result, this condition has a high economic impact on healthcare budgets, while the HRQOL of TGCT patients substantially deteriorates over time.

Response to high-dose ifosfamide in patients with advanced/recurrent Ewing sarcoma.

AIM: To determine activity and toxicity of high-dose ifosfamide (HDIFO) in recurrent or advanced Ewing sarcoma family tumors (EFT). METHODS: Thirty-seven EFT patients [median age 17 years (6-45 years)] previously treated with chemotherapy regimens including standard dose ifosfamide were enrolled. HDIFO was administered for metastatic recurrent disease in 33 patients and for progression during neoadjuvant chemotherapy in 4 patients. All patients who received two courses of 15 g/m(2) ifosfamide were evaluable for radiographic response assessed according to RECIST criteria. RESULTS: Transient Grade 4 neutropenia and thrombocytopenia in 97% and 54% HDIFO courses respectively and severe CNS toxicity in one patient were observed. Thirty-five patients were evaluable: 12 (34%) had complete (2) or partial (10) response, 11 (32%) had stable disease, and 12 (34%) had progression. CONCLUSIONS: In patients with relapsed or advanced EFT previously treated with standard dose ifosfamide HDIFO is active and it should be considered a treatment option.

Surgical Treatment of Localized-Type Tenosynovial Giant Cell Tumors of Large Joints: A Study Based on a Multicenter-Pooled Database of 31 International Sarcoma Centers.

BACKGROUND: Localized-type tenosynovial giant cell tumor (TGCT) is a rare, neoplastic disease with only limited data supporting treatment protocols. We describe treatment protocols and evaluate their oncological outcome, complications, and functional results in a large multicenter cohort of patients. A secondary study aim was to identify factors associated with local recurrence after surgical treatment. METHODS: Patients with histologically proven localized TGCT of a large joint were included if they had been treated between 1990 and 2017 in 1 of 31 tertiary sarcoma centers. Of 941 patients with localized TGCT, 62% were female. The median age at initial treatment was 39 years, and the median duration of follow-up was 34 months. Sixty-seven percent of the tumors affected the knee, and the primary treatment at the tertiary center was 1-stage open resection in 73% of the patients. Proposed factors for predicting a first local recurrence after treatment in the tertiary center were tested in a univariate analysis, and those that demonstrated significance were subsequently included in a multivariate analysis. RESULTS: The localized TGCT recurred in 12% of all cases, with local-recurrence-free rates at 3, 5, and 10 years of 88%, 83%, and 79%, respectively. The strongest factor for predicting recurrent disease was a prior recurrence (p < 0.001). Surgical treatment decreased pain and swelling in 71% and 85% of the patients, respectively, and such treatment was associated with complications in 4% of the patients. Univariate and multivariate analyses of the patients who had not undergone therapy previously yielded positive associations between local recurrence and a tumor size of ≥5 cm versus <5 cm (hazard ratio [HR] = 2.50; 95% confidence interval [CI] = 1.32 to 4.74; p = 0.005). Arthroscopy (versus open surgery) was significantly associated with tumor recurrence in the univariate analysis (p = 0.04) but not in the multivariate analysis (p = 0.056). CONCLUSIONS: Factors associated with recurrence after resection of localized-type TGCT were larger tumor size and initial treatment with arthroscopy. Relatively low complication rates and good functional outcomes warrant an open approach with complete resection when possible to reduce recurrence rates in high-risk patients. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Denosumab in advanced/unresectable giant-cell tumour of bone (GCTB): For how long?

BACKGROUND: Giant-cell tumours of bone (GCTB) are RANK/RANK-ligand (RANKL) positive, aggressive and progressive osteolytic tumours. Denosumab, a RANKL inhibitor, was FDA-approved for adults and skeletally mature adolescents with unresectable GCTB or when surgical resection is likely to result in severe morbidity. Data on long-term toxicity and activity of denosumab monthly 'GCTB-schedule' (120 mg per 12/year, 1440 mg total dose/year) are lacking. METHODS: Patients with GCTB receiving denosumab, 120 mg on days 1, 8, 15, 29 and every 4 weeks thereafter, from 2006 to 2015 treated in two centres were included. Long-term toxicity was evaluated. RESULTS: Ninety-seven patients were identified. 43 patients underwent resection of the tumour with a median time on denosumab treatment of 12 months (range 6-45 months). Fifty-four patients had unresectable GCTB's (male/female 23/31, median age 35 years [range: 13-76 years], 26% presented with lung metastases, 31% had primary tumor located to the spine, 63% were relapsed after previous surgery) with a median time on denosumab of 54 months (9-115 months). In the unresectable GCTB group, tumour control and clinical benefits were observed in all patients undergoing denosumab, whereas 40% of patients discontinuing denosumab had tumour progression after a median of 8 months (range 7-15 months). ADVERSE EVENTS: Overall, six (6%) patients developed osteonecrosis of jaw (ONJ): 1/43 (2%) in the resectable group, 5/54 (9%) in the unresectable group, with a 5-year ONJ-free survival of 92% (95% CI 84-100). Only patients with prolonged treatment experienced mild peripheral neuropathy (6/54, 11%), skin rash (5/54, 9%), hypophosphataemia (2/54, 4%) and atypical femoral fracture (2/54, 4%). CONCLUSIONS: Prolonged treatment with denosumab has sustained activity in GCTB, with a mild toxicity profile. The dose-dependent toxicity observed recommends a careful and strict monitoring of patients who need prolonged treatment. Decreased dose-intensity schedules should be further explored in unresectable GCTB.