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PURPOSE Patients with locally advanced grade 2-3 extremity/truncal soft tissue sarcomas (STS) are at high risk of recurrence. The objective of this study was to assess the efficacy and feasibility of neoadjuvant concurrent chemoradiotherapy (cCRT) in selected grade 2-3 patients with limb or trunk wall STS, and to compare this schedule to a sequential approach combining neoadjuvant chemotherapy and adjuvant radiotherapy. METHODS We retrospectively included patients who underwent neoadjuvant cCRT at two comprehensive cancer centers from 1992-2016. We then compared these results to those of patients treated with preoperative chemotherapy and postoperative radiotherapy from a third comprehensive cancer center with a propensity score matched analysis. RESULTS A total of 53 patients were treated by neoadjuvant cCRT; 58 patients could be matched with 29 patients in each treatment group after propensity score matching. Disease-free survival and overall survival at 5 years were 54.9 and 63.5%, respectively with neoadjuvant cCRT, with no significant difference when compared to the sequential treatment group. R0 resection rate was higher (90.9 vs 44.8%, p

CIC-rearranged sarcomas (CIC-RS) represent the most frequent subset of "Ewing-like" undifferentiated small round cell sarcomas. These tumors tend to be more aggressive than Ewing sarcomas. Moreover, treatment strategy can differ according to teams. The primary aim of this retrospective study was to describe the characteristics, treatments, and outcome for patients with CIC-RS included in the French NETSARC+ database.Pediatric and adult patients from 13 French centers with a diagnosis of CIC-RS were registered from October 2008 to March 2021. Patients and tumors characteristics were collected from the national network NETSARC+ database (http://netsarc.sarcomabcb.org). CIC-RS diagnosis was pathologically and molecularly confirmed with a central review by expert pathologists. Two groups of patients were studied: those treated as classical Ewing sarcomas (cohort EwS) and those treated as high-grade soft tissue sarcomas (cohort STS) according to ESMO and/or EpSSG guidelines. Survival was calculated using the Kaplan-Meier method and the log-rank test was used to compare survival.Among 79 patients, the male/female sex ratio was 0.7 and the median age at diagnosis was 27 years (range 2-87). With a median follow-up of 37 months, 39 patients died of the disease. Median overall survival from diagnosis was 18 months, with no significant difference between both cohorts (p = 0.9). Nevertheless, when focusing on patients with metastatic disease at diagnosis (N = 21), all patients from cohort STS died of disease while some patients from cohort EwS were still alive and in complete remission.FSG experience confirms the aggressive clinical course of CDS patients regardless of chemotherapy regimen.

Background Pazopanib is a tyrosine kinase inhibitor given at the approved dose of 800 mg orally once daily (OD), but often requiring individual dose adjustment due to toxicity. Limited data is available to guide prescription in older patients especially the unfit according to geriatric assessment. Patients and methods VOTRAGE is a 3 + 3 dose-escalation, open-label phase I trial of continuous OD oral administration of pazopanib to evaluate safety, PK and PD data in unfit older patients with advanced solid tumors. The primary objective was to determine the maximum tolerated dose (MTD). PK data were compared with those obtained in younger adult patients in a population PK analysis. Results Eighteen patients with a median age of 82.5 years (range 75–91) were included in three dosing cohorts (400, 600, and 800 mg daily). Three dose-limiting toxicities (DLT) were observed in five patients at 800 mg and one DLT at 600 mg in six evaluable patients. MTD was defined as level 2 dose (600 mg). Individual oral clearance was not correlated with age. A relationship was observed between the occurrence of DLT and pazopanib plasma exposure. Decreased oral bioavailability of pazopanib when given with proton-pump inhibitors was confirmed in this group of patients. Conclusion We recommend performing geriatric assessment in patients older than 75 and starting pazopanib at 600 mg per day in unfit older patients. Therapeutic drug monitoring appears very helpful in this population.

The incidence of different soft tissue sarcoma (STS) histotypes among ethnic and geographic populations has not been comprehensively investigated.Data from 2013 to 2016 were obtained from national cancer registry databases in France and Taiwan. Liposarcoma (LPS), leiomyosarcoma (LMS), angiosarcoma (AS), synovial sarcoma (SS), and malignant peripheral nerve sheath tumor (MPNST) were selected as index STSs to estimate the age-standardized incidence rates (ASRs) and other clinical features between patients.In total, 9398 patients (7148 from France and 2250 from Taiwan) were included. The ASRs of AS (5.4 vs. 2.8) and MPNST (2.0 vs. 1.0) were significantly higher in Taiwan; France had significantly higher ASRs for LPS (12.0 vs. 10.0), LMS (9.7 vs. 7.6), and SS (1.7 vs. 1.2). Patients in Taiwan with LMS or LPS were younger than their French counterparts. With regard to the distribution according to primary anatomic site, French patients had higher odds for extremity and truncal LMS (odds ratio [OR], 2.84; p .001), AS (OR, 2.67; p .001), MPNST (OR, 1.55; p = .027), and LPS (OR, 1.38; p .001) and for breast AS (OR, 10.58; p .001). Taiwanese patients had higher odds for liver AS (OR, 10.72; p .001) and uterine LMS (OR, 3.21; p .001). SS age and distribution according to primary anatomic site did not differ significantly between the French and Taiwanese populations.Significant differences in the incidence and clinical characteristics of index STS suggested that geographic (environmental) and ethnicity factors likely play a vital role in the pathogenesis of STS.

In leiomyosarcoma (LMS), a very aggressive disease, a relatively transcriptionally uniform subgroup of well-differentiated tumors has been described and is associated with poor survival. The question raised how differentiation and tumor progression, two apparently antagonist processes, coexist and allow tumor malignancy. We first identified the most transcriptionally homogeneous LMS subgroup in three independent cohorts, which we named ‘hLMS’. The integration of multi-omics data and functional analysis suggests that hLMS originate from vascular smooth muscle cells and show that hLMS transcriptional program reflects both modulations of smooth muscle contraction activity controlled by MYOCD/SRF regulatory network and activation of the cell cycle activity controlled by E2F/RB1 pathway. We propose that the phenotypic plasticity of vascular smooth muscle cells coupled with MYOCD/SRF pathway amplification, essential for hLMS survival, concomitant with PTEN absence and RB1 alteration, could explain how hLMS balance this uncommon interplay between differentiation and aggressiveness.

11571 Background: Perivascular Epithelioid Cell Neoplasms (PEComas) encompass a heterogeneous family of mesenchymal tumors. The current understanding of their natural history is limited. Previously described clinicopathological factors aimed to define benign or malignant variants, but there is a lack of prognostic factors associated with recurrence of surgically resected tumors, preventing the development of a prognostic score to better optimize patient’s management. Methods: This is a retrospective analysis of clinicopathological features from patients diagnosed with a localized PEComa, within all centers from the French Sarcoma network and one center in Belgium. We analyzed 12 clinicopathological factors in a Cox proportional hazard framework to derive a multivariate prognostic risk model for progression-free survival (PFS). We built the PEComa PROgnostic score (PEC-PRO) ranging from 0 to 5, based on the coefficients of the multivariate model. Three different prognostic groups were identified: low risk (score = 0), intermediate risk (score = 1) and high risk (score ≥2). Results: Ninety-three patients were analyzed with a median follow-up of 46 months (range, 3-253). At diagnosis, the median age was 54 years (range, 13-84), with female predominance (72%). Most common primary locations were uterus (n = 15;16%) and kidney (n = 15;16%). Median tumor size was 6.2 cm (range, 0.8-30). Among patients with reported surgical margins, 64 (73%) and 23 (27%) had R0 and R1-2 margins, respectively. The median PFS was 26 months (IC95, 2.9-124.4), with 1- and 5-year overall survival (OS) rates of 95.7% and 69.9%, respectively, while the median OS was not reached. Using univariate analyses, male gender, primary tumor size > 5 cm, high nuclear grade and cellularity, high mitotic rate > 1/50 HPF, necrosis, vascular invasion, nodal invasion, and R1-2 margins were associated with a shorter PFS. Among those, male gender (HR = 2.88; IC95 1.12-7.411, p = 0.03), vascular invasion (HR = 3.14; IC95 1.10-8.96, p = 0.034), necrosis (HR = 3.93; IC95 1.35-11.47, p = 0.015), and R1-2 margins (HR 4.47; IC95 1.60-12.46, p = 0.007) remained associated with PFS in the multivariate analysis and were included in the multivariate model. Median PFS in patients with high PEC-PRO score was 16 months as compared to 104 months and not reached for patients with intermediate and low PEC-PRO scores, respectively (p < 0.001). We also confirmed the prognostic relevance of the PEC-PRO score in terms of OS. Conclusions: Using a weighted combination of clinicopathological features, the PEC-PRO score reliably predicts the post-operative recurrence risk in patients with localized PEComas. It has the potential to better improve follow-up strategies and personalize adjuvant treatments. The findings of this retrospective analysis require validation in a prospective trial.

TPS11585 Background: Primary metastatic osteosarcoma (OS) patients are treated with a curative intent following the same principles of non-metastatic OS, while the treatment of recurrent OS is primarily surgical in the case of isolated lung metastases. When complete removal of all metastases cannot be achieved, the prognosis remains poor, with a median Progression-Free Survival (PFS) between 3 to 8 months, and therefore there is a clinical need to reduce the risk of progression after the initial treatment sequence. The REGOBONE study reported a significant PFS benefit of regorafenib (REG) compared to placebo (in osteosarcomas: median PFS: 16.4 versus 4.1 weeks) and a manageable safety profile in patients with histologically confirmed HGBS (i.e., osteosarcoma or other bone sarcomas with the exception of Ewing sarcomas, chondrosarcoma and chordoma). Methods: This multicenter trial is ongoing to study the efficacy and safety of maintenance REG in pts > = 16 years old with HGBS, without complete remission but with no progressive disease after standard treatment, either at diagnosis or at relapse. Sixty pts will be randomly allocated in a 1:1 ratio to receive either oral REG at a daily dose of 120mg or its matching placebo, continuously for a maximum of 12 months. Randomization is stratified according to the setting of the disease: initial diagnosis versus relapse. The primary objective is to compare the efficacy (PFS) between the 2 arms. The expected 4-month PFS rates are 30% in the control arm and 60% in the REGO arm (HR = 0.42). Fifty-two events will provide 87% power to show significant improvement in PFS, using a 2-sided log-rank test at a 5% level. Secondary endpoints include Overall Response Rate (ORR), Disease Control Rate (DCR), Time to Treatment Failure (TTF), Overall Survival (OS), Quality of Life (QoL), and safety profile. Radiological endpoints will be evaluated using the RECIST 1.1 with tumor assessments every 2 months (first 6 months) and then every 3 months. Translational objectives will identify predictive biomarkers for efficacy of REG as maintenance therapy. Pts of the control arm who experience disease progression may switch to receive open label REG. As of Feb 1st, 2022, 3 patients have been randomized. 14 sites of the French Sarcoma Group will participate. An amendment is being implemented to lower the age limit (12 years old) and to expand tumor types to other HGBS (Ewing sarcomas, chondrosarcomas, Undifferentiated Pleomorphic Sarcomas, Leiomyosarcomas and angiosarcomas). Clinical trial information: NCT04698785.

Prognostication is a key issue for sarcoma patients' care as it triggers the therapeutic approach including chemotherapy, which is still not standard for localized patients. Current prognostic evaluation, based on the FNCLCC grading system, has recently been improved by the CINSARC signature outperforming histology-based grading system by identifying high-risk patients in every grade, even in those considered as low. CINSARC is an expression-based signature related to mitosis and chromosome integrity with prognostic value in a wide range of cancers additional to sarcoma. First developed with frozen material, CINSARC is now coupled with NanoString technology allowing evaluation from FFPE blocks used in clinical practice. Consequently, CINSARC is currently evaluated in clinical trials with a dual objective of demonstrating the benefit of chemotherapy in sarcoma patients and testing its response prediction. Considering its overarching value in oncology, its development is welcome in any cancers where the prognostication needs to be improved.

Background While the anti-PDGFRA antibody olaratumab failed to confirm an impact on survival in unselected advanced soft tissue sarcoma (STS) patients, the level of expression and the prognosis of platelet-derived growth factor (PDGF) receptors and ligands in STS remain unclear. Patients and methods We analyzed PDGF ligands and receptors' expression levels in a series of 255 patients with different histologies of STS [gastrointestinal stromal tumor (GIST), myxoid liposarcoma (MLPS), sarcoma with complex genomics, synovial sarcoma (SyS)] with Agilent single-color micro-arrays. We explored expression levels as prognostic values in univariate and multivariate analysis using R software (version 3.4.2). Results Complex patterns of correlation of expression between ligands and receptors were observed for each histotype. PDGFA levels were highest in SyS and lowest in MLPS (P < 4 × 10−9), PDGFB and C levels were lower in GIST (P < 2 × 10−15 and P < 3 × 10−9) while PDGFD expression was similar across histological subtypes. PDGF receptor (PDGFR) A expression was lowest in MLPS (P < 0.002), whereas PDGFRB and L expressions were lowest in GIST and SyS (P < 0.0004). Interestingly, high PDGFA expression levels were associated with higher risk of metastasis (P = 0.006), whereas PDGFD levels above average were associated with a reduced risk of metastasis (P = 0.01) in univariate and multivariate analysis. Conclusions The expression of PDGF ligands and receptors varies across sarcoma histological subtypes. PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse., Highlights • The expression of PDGF ligands and receptors substantially varies across sarcoma histological subtypes. • PDGFA and D expression levels independently and inversely correlate with the risk of metastatic relapse. • The differential expression of ligands might be used as biomarker of efficacy for PDGFRα antibodies in STS.

Background The value of chemotherapy in soft tissue sarcoma (STS) remains controversial. Several expert teams consider that chemotherapy provides a survival advantage and should be proposed in high-risk (HR) patients. However, the lack of accuracy in identifying HR patients with conventional risk factors (large, deep, FNCLCC grade 3, extremity STS) is an issue that cannot be neglected. For example, while the FNCLCC grading system is a powerful tool, it has several limitations. CINSARC, a 67-gene signature, has proved to be an additional independent factor for predicting metastatic spread and outperforms histological grade. Regardless of FNCLCC grade, CINSARC stratifies patients into two separate prognostic groups: one with an excellent prognosis (low-risk (LR) CINSARC) and the other with a worse outcome (HR-CINSARC) in terms of metastatic relapse. Here we evaluate the role of chemotherapy in grade 1–2 STS patients with HR-CINSARC and assess the prognostic value of CINSARC in patients treated with standard of care. Methods CHIC is a parallel, randomized, open-label, multicenter study evaluating the effect on metastasis-free survival of adding perioperative chemotherapy to standard of care in patients with grade ½ STS sarcoma defined as HR by CINSARC. In this target selection design, 600 patients will be screened with CINSARC to randomize 250 HR-CINSARC patients between standard of care and standard of care plus chemotherapy (4 cycles of 3 weeks of intravenous chemotherapy with doxorubicin in combination with dacarbazine or ifosfamide according to histologic subtype). LR-CINSARC patients will be treated by standard of care according to the investigator. The primary endpoint is metastasis-free survival. Secondary endpoints include overall survival, disease-free survival and safety. Furthermore, the prognostic value of CINSARC will be evaluated by comparing LR-CINSARC patients to HR-CINSARC patients randomized in standard of care. Discussion CHIC is a prospective randomized phase III trial designed to comprehensively evaluate the benefit of chemotherapy in HR-CINSARC patients and to prospectively validate the prognostic value of CINSARC in grade ½ STS sarcoma patients. Trial registration ClinicalTrials.gov identifier: NCT04307277 Date of registration: 13 March 2020

The optimal threshold of surgical margins for breast malignant phyllodes tumors (MPTs) and the impact of adjuvant chemotherapy and radiotherapy were investigated.We conducted a multicenter nationwide retrospective study of all MPT cases with central pathological review within the French Sarcoma Group. Endpoints were local recurrence-free survival (LRFS), metastasis-free survival (MFS), and overall survival (OS) rates.Overall, 212 patients were included in the study. All non-metastatic patients underwent primary surgical treatment, including 58.6% of conservative surgeries. An R0 resection was achieved in 117 patients (59.4%: 26.9% of patients with 1-2 mm margins, 12.2% of patients with 3-7 mm margins, 20.3% of patients with ≥ 8 mm margins). Ninety-four patients (45%) underwent a second surgery (SS) to obtain R0 margins, with a final mastectomy rate of 72.6%. Radiotherapy and chemotherapy were performed in 91 (43.1%) and 23 patients (10.9%), respectively, but were not associated with better outcomes. Mastectomy was significantly associated with better LRFS (p 0.001). Margins of 0, 1, or 2 mm with SS were associated with better MFS (hazard ratio [HR] 0.3, p = 0.005) and OS (HR 0.32, p = 0.005) compared with margins of 0-1-2 mm without SS. Wider margins ( 8 mm) were not superior to margins of 3-7 mm (3-7 mm vs. 8 mm; HR 0.81, p = 0.69). Age (HR 2.14, p = 0.038) and tumor necrosis (HR 1.96, p = 0.047) were found to be poor prognostic factors and were associated with MFS.This study suggests that 3 mm margins are necessary and sufficient for surgical management of MPTs, and emphasizes the importance of SS to obtain clear margins in case of 0-1-2 mm margins. No impact of adjuvant chemotherapy or radiotherapy was detected in this study.

Abstract Background Brain metastases from sarcomatous lesions pose a management challenge owing to their rarity and the histopathological heterogeneity. Prognostic indices such as the Graded Prognostic Assessment (GPA) index have been developed for several primary tumour types presenting with brain metastases (e.g. lung, breast, melanoma), tailored to the specifics of different primary histologies and molecular profiles. Thus far, a prognostic index to direct treatment decisions is lacking for adult sarcoma patients with brain metastases. Methods We performed a multicentre analysis of a national group of expert sarcoma tertiary centres (French Sarcoma Group, GSF-GETO) with the participation of one Canadian and one Swiss centre. The study cohort included adult patients with a diagnosis of a bone or soft tissue sarcoma presenting parenchymal or meningeal brain metastases, managed between January 1992 and March 2012. We assessed the validity of the original GPA index in this patient population and developed a disease-specific Sarcoma-GPA index. Results The original GPA index is not prognostic for sarcoma brain metastasis patients. We have developed a dedicated Sarcoma-GPA index that identifies a sub-group of patients with particularly favourable prognosis based on histology, number of brain lesions and performance status. Conclusions The Sarcoma-GPA index provides a novel tool for sarcoma oncologists to guide clinical decision-making and outcomes research.

International audience; Soft tissue sarcomas are a group of rare and aggressive connective tissue neoplasms for which curative therapeutic opportunities are limited in advanced phase. Clinical trials assessing immunotherapy in these tumors have so far reported limited efficacy. The objective of this study is to provide a description of the immunologic landscape of sarcomas to guide the next clinical trials of immunotherapy in these diseases. The gene expression profile of 93 immune checkpoint (ICP) and membrane markers (MM) of immune cells was analyzed in a series of 253 soft tissue sarcoma (synovial sarcoma, myxoid liposarcoma, sarcoma with complex genomic and GIST) using Agilent Whole Human Genome Microarrays. The unsupervised hierarchical clustering of gene expression level was found able to properly group patients according to the histological subgroup of sarcoma, indicating that each sarcoma subgroup is associated with a specific immune signature defined by its gene expression pattern. Using the prognostic impact of CIBERSORT signature on metastatic-free survival in each subgroup, specific target could be proposed for each of the four groups: Treg through ICOS and GITR in GIST, M0 macrophages in all four sarcoma subtypes, OX40 in SS, CD40 in GIST and SS. The immune landscape of sarcoma was found to be as heterogeneous as the histotypes and molecular subtypes, but strongly correlated to the histotype. Histotype adapted immunotherapeutic approaches in each sarcoma subtypes must be considered in view of these results, consistently with the already reported specific response of histotypes of ICPs.

Background Plocabulin (PM060184) is a novel marine-derived microtubule inhibitor that acts as an antitumor agent. This first-in-human study evaluated dose-limiting toxicities (DLT) to define the maximum tolerated dose (MTD) and phase II recommended dose (RD) of plocabulin given as a 10-min infusion on Day (D) 1, D8 and D15 every four weeks. Patients and methods Forty-four patients with advanced solid tumors received plocabulin following an accelerated titration design. Results Plocabulin was escalated from 1.3 mg/m2 to 14.5 mg/m2, which was defined as the MTD. No RD was confirmed, because frequent dose delays and omissions resulted in low relative dose intensity (66%) at the 12.0 mg/m2 expansion cohort. The main DLT was grade 3 peripheral sensory neuropathy (PSN); other DLTs were grade 4 tumor lysis syndrome, grade 4 cardiac failure and grade 3 myalgia. Toxicities were mainly mild to moderate, and included abdominal pain, myalgia, fatigue, nausea, and vomiting. Myelosuppression was transient and manageable. Plocabulin had a half-life of ~4 h and a wide diffusion to peripheral tissues. Antitumor response was observed in cervix carcinoma and heavily pretreated metastatic non-small cell lung cancer patients, and disease stabilization (≥3 months) in patients with colorectal, thymic, gastrointestinal stromal and breast tumors, among others. The clinical benefit rate was 33%. Conclusion The main DLT of plocabulin was PSN, as anticipated for a tubulin-binding agent. Since encouraging antitumor activity was observed, efforts to improve toxicity and to find the RD were planned in other trials evaluating D1&D8 and D1-D3 plus D15-D17 schedules.

Background Brain metastases (BM) from adult soft tissue or bone sarcomas are rare, and sparse data exist on their prognostic factors and management. Subjects, Materials and Methods A retrospective study was conducted in 15 centers of the French Sarcoma Group, plus one Canadian and one Swiss center, to report on clinical, histological, and treatment characteristics and to identify predictive factors of outcome. Results Between 1992 and 2012, 246 patients with a median age of 50 years (range: 16–86) were managed for BM. BM included 221 cerebral and cerebellar metastases and 40 cases of meningeal sarcomatosis. The most frequent histopathological subtype was leiomyosarcoma (18.7%). Histological grade was high in 118 (48%) cases. Surgery of BM was carried out for 38 (15.5%) patients. Radiotherapy and chemotherapy were administered in 168 (68.3%) and 91 (37.0%) patients, respectively. Irrespective of treatment modality, BM were controlled in 113 patients (45.9%), including 31 partial responses (12.6%) and 18 complete responses (7.3%). The median overall survival from diagnosis of brain metastasis was 2.7 months (range: 0–133). In the multivariate analysis, the following parameters influenced overall survival: chemotherapy (hazard ratio [HR] = 0.38; 95% confidence interval [CI]: 0.26–0.48), surgery (HR = 0.40; 95% CI: 0.22–0.72), stereotactic radiotherapy (HR = 0.41; 95% CI: 0.19–0.90), whole-brain radiotherapy (HR = 0.51; 95% CI: 0.35–0.76), and grade (HR = 0.65; 95% CI: 0.43–0.98). Conclusion BM of sarcomas are rare and associated with a dismal outcome. Multidisciplinary management with chemotherapy, radiation therapy, and surgery is associated with a better survival. Implications for Practice The incidence of brain and meningeal metastasis in bone and soft tissue sarcomas is estimated between 1% and 8%. Published data are derived from small retrospective case series, often in the pediatric population. A prognostic index is important to guide both clinical decision-making and outcomes research, but one such is lacking for adult sarcoma patients with brain metastases. The current study describes brain metastasis in a large cohort of sarcoma patients. This study, conducted within the French Sarcoma Group, describes the natural history of sarcoma brain metastasis and enables the proposal of strategic recommendations for subsequent clinical trials and for the management of such patients.

Background Prediction of metastatic outcome in sarcomas is challenging for clinical management since they are aggressive and carry a high metastatic risk. A 67-gene expression signature, the Complexity INdex in SARComas (CINSARC), has been identified as a better prognostic factor than the reference pathological grade. Since it cannot be applied easily in standard laboratory practice, we assessed its prognostic value using nanoString on formalin-fixed, paraffin-embedded (FFPE) blocks to evaluate its potential in clinical routine practice and guided therapeutic management. Methods A code set consisting of 67 probes derived from the 67 genes of the CINSARC signature was built and named NanoCind®. To compare the performance of RNA-seq and nanoString (NanoCind®), we used expressions of various sarcomas (n=124, frozen samples) using both techniques and compared predictive values based on CINSARC risk groups and clinical annotations. We also used nanoString on FFPE blocks (n=67) and matching frozen and FFPE samples (n=45) to compare their level of agreement. Metastasis-free survival and agreement values in classification groups were evaluated. Results CINSARC strongly predicted metastatic outcome using nanoString on frozen samples (HR=2.9, 95% CI: 1.23–6.82) with similar risk-group classifications (86%). While more than 50% of FFPE blocks were not analyzable by RNA-seq owing to poor RNA quality, all samples were analyzable with nanoString. When similar (risk-group) classifications were measured with frozen tumors (RNA-seq) compared with FFPE blocks (84% agreement), the CINSARC signature was still a predictive factor of metastatic outcome with nanoString on FFPE samples (HR=4.43, 95% CI: 1.25–15.72). Conclusion CINSARC is a material-independent prognostic signature for metastatic outcome in sarcomas and outperforms histological grade. Unlike RNA-seq, nanoString is not influenced by the poor quality of RNA extracted from FFPE blocks. The CINSARC signature can potentially be used in combination with nanoString (NanoCind®) in routine clinical practice on FFPE blocks to predict metastatic outcome.

Background Malignant peripheral nerve sheath tumors (MPNST) are a rare subtype of soft tissue sarcoma. They can arise in irradiated fields, in patients with type 1 neurofibromatosis (NF1), or sporadically. MPNST exhibit an aggressive behaviour, and their optimal management remains controversial. An unsolved issue is whether NF1-related and sporadic forms of MPNST have a different prognosis, and should be managed differently. Material and methods Adult and paediatric patients with histologically confirmed MPNST treated between 1990 and 2013 in French cancer centres of the GSF/GETO network, were included in this retrospective study. Results A total of 353 patients (37% with NF1 and 59% with sporadic tumours) were analysed. Median age at diagnosis was 42 years (range 1–94). The majority of tumours developed in the limbs, were deep-seated and of high grade. Two hundreds and ninety four patients underwent a curative intent surgery. Among them, 60 patients (21%) had neoadjuvant treatment (mainly chemotherapy), and 173 (59%) had adjuvant treatment (mainly radiotherapy). For operated patients, median progression free and overall survival (OS) were 26.3 months and 95.8 months, respectively. In multivariate analysis, poor-prognosis factors for OS were high grade, deep location, locally advanced stage at diagnosis, and macroscopically incomplete resection (R2). NF1 status was not negatively prognostic, except in the recurrence or metastatic setting, where NF1-related MPNST patients treated with palliative chemotherapy showed worse survival than patients with sporadic forms. Conclusion To our knowledge, our series is the largest study of patients with MPNST reported to date. For operated patients, we showed a worse prognosis for NF1-related MPNST, due to different clinical features at diagnosis, more than NF1 status itself. The French sarcoma group is now conducting correlative analyses on these patients, using the latest molecular tools.

11552Background: Clear-Cell Sarcoma (CCS) is a rare soft tissue sarcoma poorly documented, with poor prognosis. Primary objective was to study the characteristics and outcomes of CCS patients (pts)...

Summary Background The benefit or harm of trabectedin discontinuation in patients with non-progressive soft-tissue sarcoma remains unclear. We report the final analysis of a phase 2 trial investigating the clinical benefit of continuation of trabectedin treatment until progression versus interruption of therapy after six treatment cycles in patients with advanced soft-tissue sarcoma. Methods For this open-label, non-comparative, multicentre, phase 2 study, eligible adult patients with advanced soft-tissue sarcomas, who had previously received doxorubicin-based chemotherapy and were able to receive trabectedin, were enrolled from 14 centres of the French Sarcoma Group. Trabectedin was administered at a dose of 1·5 mg/m 2 through a central venous line as a 24-h continuous infusion every 3 weeks. After the initial six cycles of trabectedin, patients who were free from progressive disease were randomly assigned in a 1:1 ratio either to continuous treatment or therapy interruption. Randomisation was done centrally by a computer-generated system using permuted blocks of four patients, stratified by tumour grade and performance status. Patients allocated to the interruption group were allowed to restart trabectedin in case of progressive disease. The primary endpoint was progression-free survival at 6 months after randomisation, analysed by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01303094. Results In 178 evaluable patients, 91 (51%) patients had not progressed after six cycles. Of these patients, 53 patients were randomly assigned to the two treatment groups: 27 to the continuation group and 26 to the interruption group. Overall, patients in the two groups received a similar median number of trabectedin cycles (continuation group: 11 cycles [range 6–31+] vs interruption group: 11 [range 6–23+]). After randomisation, progression-free survival at 6 months was 51·9% (95% CI 31·9–68·6) in the continuation group versus 23·1% (9·4–40·3) in the interruption group (p=0·0200). The occurrence of treatment-related grade 3 adverse events (four [16%] of 25 patients in the continuation group vs three [14%] of 21 in the interruption group) and grade 4 adverse events (one [4%] vs none) was similar in both groups. The most common grade 3 and 4 toxicities were alanine aminotransferase or aspartate aminotransferase increases (one [4%] in the interruption group vs three [14%] in the continuation group), neutropenia (two [8%] vs two [10%]), and intestinal occlusion (one [4%] vs one [5%]). Interpretation We do not recommend trabectedin discontinuation in patients with advanced, doxorubicin-refractory soft-tissue sarcoma who have not progressed after six cycles of treatment. Funding The French National Cancer Institute (INCa) and PharmaMar SA.

11055 Background: The optimal management of malignant phyllod tumors (MPT) is poorly documented. Objective:To study the characteristics and outcome of MPT patients (pts). Methods: Retrospective study from the nation-wide French sarcoma network (NetSarc) from 2000 to 2016. Inclusion criteria was central pathological review of MPT. End-points were local recurrence-free survival (LRFS), metastasis-free survival (MFS), and overall survival (OS). Results: 212 pts, from 13 centers, were included. Median age was 52.8 years (range: 16.8 - 90.5). All localized MPT pts (96.7%) underwent surgery with 41.4% of mastectomy. The median size was 5.8 cm (range: 1.5 - 30). R1/R2 resection was achieved in 40.1% pts (26.9% 1-2 mm margin, 12.2% 3-7 mm, 20.3% ≥8 mm), with 44.8% of second surgery (SS) for a final mastectomy rate of 72.6%. Presurgical biopsy was performed in 86.3% and associated with R0 resection ( p=0.044) and better LRFS ( p=0.012). Median follow-up was 4.1 years (range 0-14.8) and revealed 34 (16.6%), 48 (22.9%), 44 (20.8%) events for LRFS, MFS and OS, respectively. The 2-year OS rate was 89%. Prognostic factors found in multivariate analysis are presented in Table 1. Wider margins (≥8mm) were not associated with better outcomes. Adjuvant radiotherapy and chemotherapy were performed in 43.6% and 13.3% respectively and associated with longer LRFS, not significant in multivariate analysis. Conclusions: Mastectomy is associated with better local control, but not with MFS and OS. Age, tumor necrosis and metastatic disease are associated with poor prognosis in MPT pts. Our study suggests that margins of 3 mm are necessary and sufficient for the surgical management of MPT and emphasizes the importance of SS to obtain clear margins. [Table: see text]

11041 Background: A subset of metastatic GIST exhibit very long-term survival after imatinib (IM) introduction. The aim of this study was to analyse the clinico-biological characteristics of GIST pts alive > 10 years (yrs) after diagnosis (dx) of metastases (mets) and identify possible factors associated with long-term survival. Methods: Pts were identified from 2 sarcoma databases; NetSarc and ConticaGIST. Clinical data prospectively registered in the databases were supplemented with retrospective review of medical records. Results: We identified 141 pts (75 men, 66 women) with median age 54 (17-84) yrs and median ECOG 0 (0-2). Primary tumors (T) were all CD117+, and mainly gastric or intestinal (64 & 45 pts), with median size 10 (2-40) cm, CD34+ (82 pts), mitoses/50 HPF ≤ 5 (n = 36), or > 5 (n = 81). Genotype was documented in 82 (58%) pts with 73 (89%) KIT mutations (in exons 11,9 and 12 of 69, 3, and 1 pts respectively) and 9 WT KIT. 129 (91%) T were resected, 124 upfront, 5 post IM, with R0/R1/R2 resections in 61, 11, and 10 pts. Mets were mainly hepatic or peritoneal (78 & 51 respectively). 1st line TKI was given to 139 pts: 130 received IM; 88 (63%) within a clinical trial (CT), 41 (29%) had mets resection. Second, 3d and 4th line TKI were given to 81, 51 and 37 pts respectively, comprising 27, 7 and 10 from CT. Median number of TKIs was 2 (0-7), but 60 (44%) pts received only 1st line with no GIST progression within or after 10 yrs. 2 pts never received TKI but had mets resection. After median FU of 14.3 yrs (10-34.5), 104 remain alive, 37 died. Mean and Median OS from initial dx are 24 yrs (CI95% 21.6-27) and 20,8 yrs. Median PFS on TKIs are 127, 29, 21 and 22 mos on 1st, 2d, 3d and 4th line of TKI. In univariate analysis no factor is significantly associated with OS, but T size (≤ 10 vs > 10 cm) and oligometastatic disease (≤5 vs > 5 mets) are borderline significant (p = 0.056 and 0.07), and good PS (ECOG ≤ 1) at 2dline TKI initiation is associated with better PFS (p = 0.03). Conclusions: This large series of long-term ( > 10 yrs) survivors of metastatic GIST shows a high proportion of mets resection and a longer duration of PFS for TKI at any line. In this selected population, no prognostic factor is associated with long OS.

Malignant solitary fibrous tumors are rare soft-tissue sarcomas. They are considered as low-grade malignancies, but may display metastatic potential in 20% of the cases. In case of metastatic or locally advanced, unresectable disease, standard treatments, like anthracycline-based regimens, are poorly effective. Previous studies suggested that antiangiogenic drugs, such as sorafenib, could be efficient to treat vascular sarcomas and solitary fibrous tumors. Five patients with progressive SFT were included in this phase 2 study, and treated with sorafenib at a dose of 800 mg daily. Two patients out of the five achieved a 9 months disease control with sorafenib, while their disease had progressed within the month preceding their inclusion. Consequently, our data suggest a potential efficacy of sorafenib in SFT, Further investigation is needed to confirm these data.

10523 Background: Trabectedin (T) maintenance beyond 6 cycles (cy) of treatment in responding pts with ASTS is associated with improved outcomes (Retrospective on database analysis; ASCO 2013). Her...