KIT ATP-Binding Pocket/Activation Loop Mutations in GI Stromal Tumor: Emerging Mechanisms of Kinase Inhibitor Escape

PURPOSE

Imatinib resistance in GI stromal tumors (GISTs) is primarily caused by secondary KIT mutations, and clonal heterogeneity of these secondary mutations represents a major treatment obstacle. KIT inhibitors used after imatinib have clinical activity, albeit with limited benefit. Ripretinib is a potent inhibitor of secondary KIT mutations in the activation loop (AL). However, clinical benefit in fourth line remains limited and the molecular mechanisms of ripretinib resistance are largely unknown.

PATIENTS AND METHODS

Progressing lesions of 25 patients with GISTs refractory to ripretinib were sequenced for KIT resistance mutations. Resistant genotypes were validated and characterized using novel cell line models and in silico modeling.

RESULTS

GISTs progressing on ripretinib were enriched for secondary mutations in the ATP-binding pocket (AP), which frequently occur in cis with preexisting AL mutations, resulting in highly resistant AP/AL genotypes. AP/AL mutations were rarely observed in a cohort of progressing GIST samples from the preripretinib era but represented 50% of secondary KIT mutations in patients with tumors resistant to ripretinib. In GIST cell lines harboring secondary KIT AL mutations, the sole genomic escape mechanisms during ripretinib drug selection were AP/AL mutations. Ripretinib and sunitinib synergize against mixed clones with secondary AP or AL mutants but do not suppress clones with AP/AL genotypes.

CONCLUSION

Our findings underscore that KIT remains the central oncogenic driver even in late lines of GIST therapy. KIT-inhibitor combinations may suppress resistance because of secondary KIT mutations. However, the emergence of KIT AP/AL mutations after ripretinib treatment calls for new strategies in the development of next-generation KIT inhibitors.

Improved nationwide survival of sarcoma patients with a network of reference centers

BACKGROUND

We investigated the impact of the implementation of a network of reference centers for sarcomas (NETSARC) on the care and survival of sarcoma patients in France since 2010.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized multidisciplinary tumor boards (MDTBs), funded by the French National Cancer Institute (INCa) since 2010. Its aims are to improve the quality of diagnosis and care of sarcoma patients. Patients' characteristics, treatments, and outcomes are collected in a nationwide database. The objective of this analysis was to compare the survival of patients in three periods: 2010-2012 (non-exhaustive), 2013-2015, and 2016-2020.

RESULTS

A total of 43 975 patients with sarcomas, gastrointestinal stromal tumors (GISTs), or connective tissue tumors of intermediate malignancy were included in the NETSARC+ database since 2010 (n = 9266 before 2013, n = 12 274 between 2013 and 2015, n = 22 435 in 2016-2020). Median age was 56 years, 50.5% were women, and 13.2% had metastasis at diagnosis. Overall survival was significantly superior in the period 2016-2020 versus 2013-2015 versus 2010-2012 for the entire population, for patients >18 years of age, and for both metastatic and non-metastatic patients in univariate and multivariate analyses (P < 0.0001). Over the three periods, we observed a significantly improved compliance to clinical practice guidelines (CPGs) nationwide: the proportion of patients biopsied before surgery increased from 62.9% to 72.6%; the percentage of patients presented to NETSARC MDTBs before first surgery increased from 31.7% to 44.4% (P < 0.0001). The proportion of patients with R0 resection on first surgery increased (from 36.1% to 46.6%), while R2 resection rate decreased (from 10.9% to 7.9%), with a better compliance and improvement in NETSARC centers.

CONCLUSIONS

The implementation of the national reference network for sarcoma was associated with an improvement of overall survival and compliance to guidelines nationwide in sarcoma patients. Referral to expert networks for sarcoma patients should be encouraged, though a better compliance to CPGs can still be achieved.

PEC-PRO: A new prognostic score from a series of 87 patients with localized perivascular epithelioid cell neoplasms (PEComas) treated with curative intent

BACKGROUND

Perivascular epithelioid cell neoplasms (PEComas) encompass a heterogeneous family of mesenchymal tumors. Previously described clinicopathologic features aimed at distinguishing benign from malignant variants but lacked prognostic value.

METHODS

This retrospective analysis examined clinicopathologic data from patients who had localized PEComa across French Sarcoma Network centers. The authors analyzed 12 clinicopathologic features in a Cox proportional hazard framework to derive a multivariate prognostic risk model for event-free survival (EFS). They built the PEComa prognostic score (PEC-PRO), in which scores ranged from 0 to 5, based on the coefficients of the multivariate model. Three groups were identified: low risk (score = 0), intermediate risk (score = 1), and high risk (score ≥ 2).

RESULTS

Analyzing 87 patients who had a median 46-month follow-up (interquartile range, 20-74 months), the median EFS was 96.5 months (95% confidence interval [CI], 47.1 months to not applicable), with 2-year and 5-year EFS rates of 64.7% and 58%, respectively. The median overall survival was unreached, with 2-year and 5-year overall survival rates of 82.3% and 69.3%, respectively. The simplified Folpe classification did not correlate with EFS. Multivariate analysis identified three factors affecting EFS: positive surgical margins (hazard ratio [HR], 5.17; 95% CI, 1.65-16.24; p = .008), necrosis (HR, 3.94; 95% CI, 1.16-13.43; p = .030), and male sex (HR, 3.13; 95% CI, 1.19-8.27; p = 0.023). Four variables were retained in the prognostic model. Patients with low-risk PEC-PRO scores had a 2-year EFS rate of 93.7% (95% CI, 83.8%-100.0%), those with intermediate-risk PEC-PRO scores had a 2-year EFS rate of 67.4% (95% CI, 53.9%-80.9%), and those with high-risk PEC-PRO scores had a 2-year EFS rate of 2.3% (95% CI, 0.0%-18.3%).

CONCLUSIONS

The PEC-PRO score reliably predicts the risk of postoperative recurrence in patients with localized PEComa. It has the potential to improve follow-up strategies but requires validation in a prospective trial.

Sclerosing Epithelioid Fibrosarcoma (SEF) versus Low Grade Fibromyxoid Sarcoma (LGFMS): Presentation and outcome in the nationwide NETSARC+ series of 330 patients over 13 years

Sclerosing Epithelioid Fibrosarcoma (SEF) and Low Grade Fibromyxoid Sarcoma (LGFMS) are ultrarare sarcomas sharing common translocations whose natural history are not well known. We report on the nationwide exhaustive series of 330 patients with SEF or LGFMS in NETSARC+ since 2010.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized multidisciplinary tumor boards (MDTB). Since 2010, (i) pathological review has been mandatory for sarcoma,and (ii) tumour/patients' characteristics have been collected in the NETSARC+ nationwide database. The characteristics of patients with SEF and LGFMS and their outcome are compared.

RESULTS

35/73 (48%) and 125/257(49%) of patients with SEF and LGFMS were female. More visceral, bone and trunk primary sites were observed in SEF (p < 0.001). 30% of SEF vs 4% of LGFMS patients had metastasis at diagnosis (p < 0.0001). Median size of the primary tumor was 51 mm (range 10-90) for LGFMS vs 80 (20-320) for SEF (p < 0.001). Median age for LGFMS patients was 12 years younger than that of SEF patients (43 [range 4-98] vs 55 [range 10-91], p < 0.001). Neoadjuvant treatment was more often given to SEF (16% vs 9%, p = 0.05). More patients with LGFMS were operated first in reference centers (51% vs 26%, p < 0.001). The R0 rate on the operative specimen was 41% in LGFMS vs 16% in SEF (p < 0.001). Median event-free survival (EFS) of patients with SEF and LGFMS were 32 vs 136 months (p < 0.0001). The median overall survival (OS) was not reached. Fifty-months OS was 93% vs 81% for LGFMS vs SEF (p = 0.05). Median OS was 77 months after first relapse, similar for SEF and LGFMS. In multivariate analysis, age, tumor size, metastasis at diagnosis were independent prognostic factors for OS in LGFMS.

CONCLUSIONS

Although sharing close molecular alterations, SEF and LGFMS have a different natural history, clinical presentation and outcome, with a higher risk of metastatic relapse in SEF. Survival after relapse is longer than with other sarcomas, and similar for SEF and LGFMS.

Efficacy of immune checkpoint inhibitors in alveolar soft-part sarcoma: results from a retrospective worldwide registry

BACKGROUND

Conventional cytotoxic drugs are not effective in alveolar soft-part sarcoma (ASPS). Immune checkpoint (programmed cell death protein 1/programmed death-ligand 1) inhibitors (ICIs) are promising drugs in ASPS. A worldwide registry explored the efficacy of ICI in ASPS.

MATERIALS AND METHODS

Data from adult patients diagnosed with ASPS and treated with ICI for advanced disease in expert sarcoma centers from Europe, Australia and North America were retrospectively collected, including demographics and data related to treatments and outcome.

RESULTS

Seventy-six ASPS patients, with a median age at diagnosis of 25 years (range 3-61 years), were registered. All patients received ICI for metastatic disease. Immunotherapy regimens consisted of monotherapy in 38 patients (50%) and combination in 38 (50%) (23 with a tyrosine kinase inhibitor). Among the 68 assessable patients, there were 3 complete responses and 34 partial responses, translating into an overall response rate of 54.4%. After a median follow-up of 36 months [95% confidence interval (CI) 32-40 months] since the start of immunotherapy, 45 (59%) patients have progressed on ICI, with a median progression-free survival (PFS) of 16.3 months (95% CI 8-25 months). Receiving ICI in first line (P = 0.042) and achieving an objective response (P = 0.043) correlated with a better PFS. Median estimated overall survival (OS) from ICI initiation has not been reached. The 12-month and 24-month OS rates were 94% and 81%, respectively.

CONCLUSIONS

This registry constitutes the largest available series of ASPS treated with ICI. Our results suggest that the ICI treatment provides long-lasting disease control and prolonged OS in patients with advanced ASPS, an ultra-rare entity with limited active therapeutic options.

Epithelioid hemangio-endothelioma (EHE) in NETSARC: The nationwide series of 267 patients over 12 years

EPITHELIOID HEMANGIOENDOTHELIOMA

A NATIONWIDE STUDY: Epithelioid hemangioendothelioma (EHE) is an ultrarare sarcoma whose natural history and treatment is not well defined. We report on the presentation and outcome of 267 patients with EHE in the NETSARC+ network since 2010 in France.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centres with specialised multidisciplinary tumour boards (MDTB), funded by the French National Cancer Institute (NCI), Institut National du Cancer (INCA). Since 2010, presentation to an MDTB and second pathological review are mandatory for sarcoma patients. Patients' characteristics are collected in a nationwide database regularly monitored with stable incidence since 2013. The characteristics of patients with EHE at diagnosis are presented as well as progression-free survival (PFS), overall survival (OS), and outcome under treatment.

RESULTS

Two hundred and sixty-seven patients with EHE were included in the NETSARC+ database since 2010. Median age in the series was 51 (range 10-90) years, 58% were women. Median tumour size was 37 mm (4-220). Forty-eight percent, 42%, and 10% were visceral, soft parts, or bone primaries. The most frequent sites were liver (28%), lung (13%). 40% were reported to have systemic (i.e. multifocal or metastatic disease) at diagnosis. With a median follow-up of 20 months, OS and PFS rates at 24 months were 82% and 67%, with 10-year projected OS and PFS of 62% and 21% respectively. Male and M+ patients at diagnosis had a significantly worse OS, but not PFS. Local treatment was associated with a favourable survival in localised but not in patients with advanced stage at diagnosis. For 23 patients receiving medical treatment, PFS and OS were 50.2% and 33.2% at 60 months were respectively.

CONCLUSIONS

EHE is a frequently metastatic sarcoma at diagnosis with a unique natural history. This study shows in a nationwide series over 12 years that most patients progressed but are still alive at 10 years, both in localised and metastatic stages.

Prognostic Factors for Local Recurrence after Cryoablation of Desmoid Tumors

PURPOSE

To determine the risk factors for local of adult patients treated for desmoid tumors by cryoablation.

MATERIALS AND METHODS

Eighty-four patients treated for nonabdominopelvic desmoid tumors by cryoablation from July 2012 to July 2020 were included in a retrospective study. The population was composed of 64 women (76.19%) and 20 men (23.81%), aged from 16 to 75 years (median, 35 years ± 14.25). Each patient underwent preprocedural gadolinium-enhanced magnetic resonance imaging and was followed up to 36 months with the same technique. Clinical features, such as tumor size and previous treatment, epidemiological features, and the technical parameters of cryoablation, were studied.

RESULTS

Local relapse was found in 19 (22.62%) of 84 patients. The 12-, 24-, and 36-month progression-free survival rates were 89% (95% confidence interval [CI], 79-94), 74% (95% CI, 60-83), and 68% (95% CI, 53-79), respectively. In univariate analysis, significant prognostic factors associated with local recurrence were non-abdominal wall location (P = .042), debulking strategy (P = .0105), risk of visceral injury (P = .034) or peripheral nerve injury during cryoablation (P = .033), previous radiation therapy (P = .043), and treatment before 2016 (P = .008). In multivariate analysis, abdominal wall tumors displayed the best outcome, whereas the neck and trunk showed a high rate of recurrence (hazard ratio, 7.307 [95% CI, 1.396-38.261]).

CONCLUSIONS

The local recurrence of desmoid tumors after cryoablation depends on a number of prognostic factors, in particular, a non-abdominal wall location of the tumor and previous local treatment such as surgery or radiation therapy.

Evolution of Patterns of Care and Outcomes in the Real-Life Setting for Patients with Metastatic GIST Treated in Three French Expert Centers over Three Decades

Gastrointestinal stromal tumors (GIST) are rare mesenchymal tumors characterized by KIT or PDGFRA mutations. Over three decades, significant changes in drug discovery and loco-regional (LR) procedures have impacted treatment strategies. We assessed the evolution of treatment strategies for metastatic GIST patients treated in the three national coordinating centers of NetSarc, the French network of sarcoma referral centers endorsed by the National Institute of Cancers, from 1990 to 2018. The primary objective was to describe the clinical and biological profiles as well as the treatment modalities of patients with metastatic GIST in a real-life setting, including access to clinical trials and LR procedures in the metastatic setting. Secondary objectives were to assess (1) patients' outcome in terms of time to next treatment (TNT) for each line of systemic treatment, (2) patients' overall survival (OS), (3) evolution of patients' treatment modalities and OS according to treatment access: <2002 (pre-imatinib approval), 2002-2006 (pre-sunitinib approval), 2006-2014 (pre-regorafenib approval), post 2014, and (4) the impact of clinical trials and LR procedures on TNT and OS in the metastatic setting. 1038 patients with a diagnosis of GIST made in one of the three participating centers between 1990 and 2018 were included in the national prospective database. Among them, 492 patients presented metastasis, either synchronous or metachronous. The median number of therapy lines in the metastatic setting was 3 (range 0-15). More than half of the patients (55%) participated in a clinical trial during the course of their metastatic disease and half (51%) underwent additional LR procedures on metastatic sites. The median OS in the metastatic setting was 83.4 months (95%CI [72.7; 97.9]). The median TNT was 26.7 months (95%CI [23.4; 32.3]) in first-line, 10.2 months (95%CI [8.6; 11.8]) in second line, 6.7 months (95%CI [5.3; 8.5]) in third line, and 5.5 months (95%CI [4.3; 6.7]) in fourth line, respectively. There was no statistical difference in OS in the metastatic setting between the four therapeutic periods (log rank, p = 0.18). In multivariate analysis, age, AFIP Miettinen classification, mutational status, surgery of the primary tumor, participation in a clinical trial in the first line and LR procedure to metastatic sites were associated with longer TNT in the first line, whereas age, mitotic index, mutational status, surgery of the primary tumor and LR procedure to metastatic sites were associated with longer OS. This real-life study advocates for early reference of metastatic GIST patients to expert centers to orchestrate the best access to future innovative clinical trials together with LR strategies and further improve GIST patients' survival.

Radiotherapy in bone sarcoma: the quest for better treatment option

Bone sarcomas are rare tumors representing 0.2% of all cancers. While osteosarcoma and Ewing sarcoma mainly affect children and young adults, chondrosarcoma and chordoma have a preferential incidence in people over the age of 40. Despite this range in populations affected, all bone sarcoma patients require complex transdisciplinary management and share some similarities. The cornerstone of all bone sarcoma treatment is monobloc resection of the tumor with adequate margins in healthy surrounding tissues. Adjuvant chemo- and/or radiotherapy are often included depending on the location of the tumor, quality of resection or presence of metastases. High dose radiotherapy is largely applied to allow better local control in case of incomplete primary tumor resection or for unresectable tumors. With the development of advanced techniques such as proton, carbon ion therapy, radiotherapy is gaining popularity for the treatment of bone sarcomas, enabling the delivery of higher doses of radiation, while sparing surrounding healthy tissues. Nevertheless, bone sarcomas are radioresistant tumors, and some mechanisms involved in this radioresistance have been reported. Hypoxia for instance, can potentially be targeted to improve tumor response to radiotherapy and decrease radiation-induced cellular toxicity. In this review, the benefits and drawbacks of radiotherapy in bone sarcoma will be addressed. Finally, new strategies combining a radiosensitizing agent and radiotherapy and their applicability in bone sarcoma will be presented.

Pembrolizumab in patients with rare and ultra-rare sarcomas (AcSé Pembrolizumab): analysis of a subgroup from a non-randomised, open-label, phase 2, basket trial

BACKGROUND

Sarcoma is a heterogeneous group of diseases with few treatment options. Immunotherapy has shown little activity in studies including unselected sarcomas, but immune checkpoint blockers have shown activity in specific histotypes. We evaluated the activity of pembrolizumab in rare and ultra-rare sarcomas.

METHODS

AcSé Pembrolizumab is an ongoing phase 2, basket, multitumour study investigating the activity of pembrolizumab monotherapy in rare cancers. Here, we report the results obtained in patients with selected histotypes of rare sarcomas (incidence of less than one case per 1 000 000 people per year) recruited at 24 French hospitals. Key inclusion criteria were age 15 years or older, Eastern Cooperative Oncology Group performance status of 0-1, and advanced disease that was untreated and resistant to treatment. Patients were given pembrolizumab 200 mg intravenously on day 1 of every 21-day cycle for a maximum of 24 months. The primary endpoint was objective response rate at week 12 using Response Evaluation Criteria in Solid Tumours version 1.1, assessed by local investigators. The primary endpoint and safety were analysed in the intention-to-treat population. The AcSé Pembrolizumab study is registered with ClinicalTrials.gov, NCT03012620.

FINDINGS

Between Sept 4, 2017, and Dec 29, 2020, 98 patients were enrolled, of whom 97 received treatment and were included in analyses (median age 51 years [IQR 35-65]; 53 [55%] were male; 44 [45%] were female; no data were collected on race or ethnicity). 34 (35%) patients had chordomas, 14 (14%) had alveolar soft part sarcomas, 12 (12%) had SMARCA4-deficient sarcomas or malignant rhabdoid tumours, eight (8%) had desmoplastic small round cell tumours, six (6%) had epithelioid sarcomas, four (4%) had dendritic cell sarcomas, three (3%) each had clear cell sarcomas, solitary fibrous tumours, and myxoid liposarcomas, and ten (10%) had other ultra-rare histotypes. As of data cutoff (April 11, 2022), median follow-up was 13·1 months (range 0·1-52·8; IQR 4·3-19·7). At week 12, objective response rate was 6·2% (95% CI 2·3-13·0), with no complete responses and six partial responses in the 97 patients. The most common grade 3-4 adverse events were anaemia (eight [8%] of 97), alanine aminotransferase and aspartate aminotransferase increase (six [6%]), and dyspnoea (five [5%]). 86 serious adverse events were reported in 37 patients. Five deaths due to adverse events were reported, none of which were determined to be related to treatment (two due to disease progression, two due to cancer, and one due to unknown cause).

INTERPRETATION

Our data show the activity and manageable toxicity of pembrolizumab in some rare and ultra-rare sarcoma histotypes, and support the PD-1/PD-L1 pathway as a potential therapeutic target in selected histotypes. The completion of the basket study will provide further evidence regarding the activity and toxicity of pembrolizumab in identified rare types of cancer.

FUNDING

The Ligue contre le cancer, INCa, MSD.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

ESR1 Rearrangement as a Diagnostic and Predictive Biomarker in Uterine Tumor Resembling Ovarian Sex Cord Tumor: A Report of Four Cases

UTROSCT are a rare entity that can sometimes present as metastatic disease. Hormonal therapy may address this issue.

Comprehensive Immune Profiling Unveils a Subset of Leiomyosarcoma with "Hot" Tumor Immune Microenvironment

Purpose: To investigate the immune biomarker in Leiomyosarcoma (LMS), which is rare and recognized as an immune cold cancer showing a poor response rate (<10%) to immune checkpoint inhibitors (ICIs). However, durable response and clinical benefit to ICIs has been observed in a few cases of LMS, including, but not only, LMS with tertiary lymphoid structure (TLS) structures. Patients and methods: We used comprehensive transcriptomic profiling and a deconvolution method extracted from RNA-sequencing gene expression data in two independent LMS cohorts, the International Cancer Genome Consortium (ICGC, N = 146) and The Cancer Genome Atlas (TCGA, N = 75), to explore tumor immune microenvironment (TIME) in LMS. Results: Unsupervised clustering analysis using the previously validated two methods, 90-gene signature and Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT), identified immune hot (I-H) and immune high (I-Hi) LMS, respectively, in the ICGC cohort. Similarly, immune active groups (T-H, T-Hi) were identified in the TCGA cohort using these two methods. These immune active ("hot") clusters were significantly associated, but not completely overlapping, with several validated immune signatures such as sarcoma immune class (SIC) classification and TLS score, T cell inflamed signature (TIS) score, immune infiltration score (IIS), and macrophage score (M1/M2), with more patients identified by our clustering as potentially immune hot. Conclusions: Comprehensive immune profiling revealed a subset of LMS with a distinct active ("hot") TIME, consistently associated with several validated immune signatures in other cancers. This suggests that the methodologies that we used in this study warrant further validation and development, which can potentially help refine our current immune biomarkers to select the right LMS patients for ICIs in clinical trials.

Efficacy and Safety of Adjuvant Radiotherapy in Re-excised Soft-tissue Sarcoma After Unplanned Resection

INTRODUCTION

The objective of this study was to evaluate the efficacy and safety of adjuvant radiotherapy (aRT) in patients with soft-tissue sarcoma (STS) re-excised after unplanned tumor resection (UPR).

MATERIALS AND METHODS

From 2000 to 2015, we retrospectively evaluated patients with STS of limb or trunk who underwent post-UPR re-excision in our expert center and received or not aRT.

RESULTS

Median follow-up was 121 months (IQR 94-165). Among the 145 patients, 37 were not treated with aRT (no-RT) and 108 received aRT with a median radiation dose of 50 Gy (IQR 50-60). At 10 years, patients in the aRT and no-RT groups showed a cumulative incidence of local failure (10y-LF) of 14.7% and 37.7%, and a local recurrence-free survival (10y-LRFS) of 61.3% and 45.8%, respectively. Multivariate analysis identified aRT and age ≥70 years as independent predictors of both LF and LRFS, while grade 3 and deep-seated tumor were independent predictors of LRFS. In overall population, 10-year distant metastasis-free survival (10y-DMFS) and overall survival (10y-OS) were 63.7% and 69.4%. In multivariate analyses, age ≥70 years, grade 3, and deep-seated lesion were associated with shorter DMFS and OS. Acute severe adverse events were not significantly increased in aRT group (14.8% vs. 18.1%, P = .85) but dramatically increased if radiation dose exceeded 50 Gy (risk ratio 2.96 compared to ≤50 Gy, P = .04).

CONCLUSION

In STS patients re-excised after UPR, 50 Gy aRT was safe and associated with reduced LF and longer LRFS. It seems to be beneficial even in absence of residual disease or in absence of initial adverse prognostic factors.

Natural history and treatment efficacy in an ambispective case series of NTRK-rearranged mesenchymal tumors

BACKGROUND

Apart for infantile fibrosarcoma (IFS), very little is known about NTRK-rearranged mesenchymal tumors (NMTs). The objective of this study is to describe the distribution, characteristics, natural history, and prognosis of NMT.

PATIENTS AND METHODS

This study was carried out as a translational research program, retrospectively from a cohort of 500 soft tissue sarcoma (STS; excluding IFS) and prospectively both in routine practice and from the RNASARC molecular screening program (N = 188; NCT03375437).

RESULTS

Using RNA-sequencing, NTRK fusion was detected in 16 patient tumors diagnosed as STS: 8 samples of sarcoma with simple genomics (4 NTRK-rearranged spindle cell neoplasm, 3 ALK/ROS wild-type inflammatory myofibroblastic tumor, and 1 quadruple Wild-type gastrointestinal stromal tumor) and 8 samples of sarcomas with complex genomics (dedifferentiated liposarcoma, intimal sarcoma, leiomyosarcoma, undifferentiated pleomorphic sarcoma, high-grade uterine sarcoma, malignant peripheral nerve sheath tumor). Among the eight patients with simple genomics, four were treated with tyrosine receptor kinase inhibitor (TRKi) at different stages of the disease and all benefited from the treatment, including one complete response. Among the eight other patients, six evolved with metastatic spreading and the median metastatic survival was 21.9 months, as classically reported in these tumor types. Two of them received a first-generation TRKi without objective response.

CONCLUSIONS

Our study confirms low frequency and histotype diversity of NTRK fusion in STS. While the activity of TRKi in simple genomics NMT is confirmed, our clinical data encourage subsequent studies focusing on the biological relevance of NTRK fusions in sarcomas with complex genomics together with the efficacy of TRKi in this population.

Abstract 6071: Whole-exome RNA sequencing of metastatic synovial sarcomas reveals heterogeneous transcriptomic profile and targetable co-alterations: Cohort study from the French Sarcoma Group

Introduction: Synovial Sarcoma (SS) is a rare and aggressive disease that predominantly occurs in young adult. SS are characterized by a pathognomonic t(X:18) translocation leading SS18: SSX1/2/4 fusion. Small studies (n&lt;100) described molecular background beyond this fusion in patients and the transcriptomic profile of SS remains poorly known. The aim of our study is to provide a large cohort analyzing transcriptomic and co-alterations to better understand and treat SS.

Methods: We present a clinico-biological cohort study including all adult patients with histologically confirmed diagnosis of afvanced SS from January 2000, registered in the French Sarcoma database (NETSARC+) and with available formalin-fixed paraffin embedded (FFPE) archival tumor samples and clinical data. FFPE tumor samples were analyzed by dedicated whole-exome RNA-sequencing (WERS) to assess transcriptomic, small nucleotide variation (SNV) and fusions.

Results: 122 patients (133 samples) met the study criteria, including 11 patients with paired primary-metastatic tumor samples. Clinical characteristics (age, sex, tumor grade, primary and metastasis site distribution) were consistent with expected SS population. The SS18:SSX1/2/4 fusion was found in all patient (90% by WERS and if negative, by FISH). Unsupervised analyses of transcriptomic data by principal component analyses, hierarchical sample clustering or UMAP revealed heterogeneity in gene expression. Clinical factors (age, sex, grade, tumor type, complete response to treatment, survival) did not correlate with transcriptomic profiles. Immune cell analyses confirmed a low infiltration of immune cells, notably poor in CD8+ T cells. Cancer testis antigens such as NYESO-1, MAGE-A4 were both expressed with a heterogeneous co-expression of other CTAs across samples. In the 11 primary-metastatic paired- samples, no gene pathway was found differentially expressed between primary and metastatic samples cohort with the exception of lung tissue specific genes. Comparing chemotherapy-naïve versus pre-treated samples did not identify differential expression of specific genes across samples. Single Nucleotide Variant analyses was reliable on 84% FFPE samples and revealed an overall low Tumor Mutational Burden with some samples harboring canonical oncogene pathogenic mutations of BTK, RAS, NF1, RB1 as well as in DNA repair pathway(15% spanning over ATM ATR,CHK2, BRCA1/2 PALB2 CHK2, FANCM, RAD51), PI3K pathways (PI3KCA E545K) and other poorly described in SS.

Conclusion: Investigating the largest cohort of metastatic SS by whole-exome RNA-sequencing, revealed Synovial Sarcoma, usually classified as “simple genomic sarcoma” is a translocation-related sarcoma harboring heterogeneous transcriptomic and numerous SNV co-alterations including targetable mutations.

Citation Format: Helene Vanacker, Mehdi Brahmi, Yannick Le Meitour, Julien Bollard, Valery Attignon, Alexandra Meurgey, Myriam Jean-Denis, Laurie Tonon, Shibani Pokras, Erika Klohe, Michael Nathenson, Kristin Blouch, Ioanna Eleftheriadou, Jean-Yves Blay, Franck Tirode, Armelle Dufresne. Whole-exome RNA sequencing of metastatic synovial sarcomas reveals heterogeneous transcriptomic profile and targetable co-alterations: Cohort study from the French Sarcoma Group. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6071.

Abstract 3887: ATP-binding pocket substitutions as secondary or tertiary in-cis mutations are major on-target ripretinib resistance mechanisms in gastrointestinal stromal tumor

Introduction: Ripretinib (Rip) is a kinase inhibitor with broad preclinical activity against mutant KIT. Based on the INVICTUS trial, Rip was approved for patients with Gastrointestinal Stromal Tumors (GIST) after treatment with 3 or more kinase inhibitors. Most patients in this ≥4th-line setting progress on Rip within one year. Here, we characterized Rip-progressing GIST samples to identify resistance mechanisms.

Methods: Progressing lesions in 25 patients were analyzed by NGS after Rip failure. KIT mutations (muts) were recapitulated by gene editing. Activities of Rip, sunitinib (SU), and novel TKIs were characterized by cell viability assays and immunoblot. Mutagenesis experiments were performed using ENU. SU- and Rip-resistant cell lines were pooled and treated with various regimens, with clonal composition deconvoluted by cDNA-based amplicon sequencing.

Results: 19/25 Rip-progressing GISTs displayed muts in the ATP-binding pocket (ATP-BP; e13/14). Four of these had pre-existing muts in the activation loop (AL; e17/18), which were confirmed to be in-cis with the primary and ATP-BP muts (triple in cis; TIC). Mutagenesis screens using a double KIT-mutant GIST line (e11 + AL) as a starting point confirmed that TIC-muts are a predominant escape mechanism when treated with Rip. A GIST subline (T1-triple) with TIC-muts in e11, e18 (A829P), and e13 (V654A) was highly resistant to Rip (GR50 &gt; 2µM). Structural analyses of ATP-BP muts suggest steric interference and loss of van der Waals interactions that impede Rip binding and thereby confer Rip resistance. Another 3/25 Rip-progressing GISTs harbored pathogenic KIT muts in e9 only. A novel GIST cell line with primary KIT e9 mut (T1-e9) was 14-fold less sensitive to Rip than isogenic e11-driven cells (GR50 = 115 vs 8nM). Notably, adding a typical AL mut to T1-e9 (T1-e9-N822K) sensitized the cells to Rip (GR50 = 20nM). Immunoblots showed &gt;95% inhibition of phospho-KIT in AL-mutant cell lines at Rip 100nM, whereas inhibition was weaker in T1-e9 (77%) and T1-V654A (46%), and absent in T1-triple. A compound screen of FDA-approved kinase inhibitors identified Nintedanib (NIN) as the most active compound against T1-triple. Clonal outgrowth assays of mixed cultures revealed SU (93% inhibition), and a weekly switch between Rip and either SU (96%) or NIN (79%) as the most effective inhibitors of pooled cell growth.

Conclusions: KIT e9 primary muts and e13/14 (ATP-BP) secondary muts are enriched in post-progression biopsies following Rip treatment. KIT TIC-muts are novel frequent events driving GIST clinical progression and confer a high degree of resistance. Strategies to overcome resistance may include combinations or sequences of approved drugs, and novel drugs that more efficiently inhibit TIC-mutant KIT.

Citation Format: Thomas Mühlenberg, Johanna Falkenhorst, Tom Schulz, Benjamin S. Fletcher, Alina Teuber, Dawid Krzeciesa, Isabella Klooster, Jonas Lategahn, Wen-Bin Ou, Meijun Lundberg, Margaret von Mehren, Susanne Grunewald, Alicia I. Tüns, Mehdi Brahmi, Michael C. Heinrich, Cesar Serrano, Hans-Ulrich Schildhaus, Sonja Sievers, Jürgen Treckmann, Lydia Wilson, Chandrajit P. Raut, Adrian Marino-Enriquez, Suzanne George, Daniel Rauh, Jonathan A. Fletcher, Sebastian Bauer. ATP-binding pocket substitutions as secondary or tertiary in-cis mutations are major on-target ripretinib resistance mechanisms in gastrointestinal stromal tumor. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3887.

Immunotherapy for Soft Tissue Sarcomas: Anti-PD1/PDL1 and Beyond

Sarcomas gather a heterogeneous group of mesenchymal malignant tumors including more than 150 different subtypes. Most of them represent aggressive tumors with poor prognosis at the advanced stage, despite the better molecular characterization of these tumors and the development of molecular-driven therapeutic strategies. During the last decade, immunotherapy has been developed to treat advanced cancers, mainly thanks to immune checkpoint inhibitors (ICI) such as anti-PD1/PDL1 and later to adoptive immune cell therapies. In this review, we aim to summarize the state of the art of immunotherapy in soft tissue sarcomas (STS). Overall, the clinical trials of ICI that included a wide diversity of STS subtypes reported limited efficacy with some outlying responders. Both emerging biomarkers are of interest in selecting good candidates and in the development of combination therapies. Finally, the recent breakthroughs of innovative adoptive therapies in STS seem highly promising.

Staging of newly diagnosed Ewing sarcoma: Results of bone marrow aspiration and biopsy versus (18)FDG-PET/CT imaging for bone marrow involvement

BACKGROUND

Ewing sarcoma (ES) is an aggressive bone or extraosseous tumour with an unfavourable prognosis when bone marrow metastases are present at diagnosis. The gold standard diagnosis for bone marrow (BM) involvement is cytological and pathological analysis through bone marrow aspiration and biopsy (BMAB). Several recent studies suggest that these invasive and painful procedures could be replaced by 18F-fluorodeoxyglucose-positron emission tomography/computed tomography ((18)FDG-PET/CT), as this nuclear imaging technique is highly sensitive at detecting bone and extraosseous metastases of ES.

METHODS

In order to study the precision of (18)FDG-PET/CT in the evaluation of bone marrow metastases at diagnosis, we compared the imaging results with cytological/histological analyses performed on BM samples. We retrospectively studied 180 patients with ES recorded at the Léon Bérard Centre over the past 10 years, who were evaluated by (18)FDG-PET/CT and BMAB at diagnosis.

RESULTS

Of the 180 patients, 13 displayed marrow metastases by cytological/histological examination, and only one of these did not have (18)FDG-PET/CT signs of bone marrow involvement, whereas the 167 remaining patients without marrow metastasis all had a negative (18)FDG-PET/CT, except for one. Hence, the sensitivity and specificity of (18)FDG-PET/CT in these patients was 92.3% and 99.4%, respectively. The overall survival at five years of all patients was 67.4% but decrease to 38.5% in the group with bone marrow metastases.

CONCLUSION

Given the results presented herein the bone sarcoma group of the French Sarcoma Group suggests that invasive BMAB no longer be systematically performed for the staging at the diagnosis of ES.

Patterns of care and outcome of CIC ‐rearranged sarcoma patients: A nationwide study of the French sarcoma group

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

FSG experience confirms the aggressive clinical course of CDS patients regardless of chemotherapy regimen.

Expanding the molecular spectrum of tenosynovial giant cell tumors

Background

While great advances in clinical and pathological description of tenosynovial giant cell tumors (TGCT) have been made, TGCT molecular heterogeneity represents an ongoing challenge. The canonical oncogenic fusion CSF1::COL6A3 is not systematically observed, suggesting that other oncogenic mechanisms are involved in tumorigenesis. This study aims to explore by RNA sequencing a retrospective series of tumors diagnosed as TGCT, in order to provide a better description of their molecular landscape and to correlate molecular features with clinical data.

Methods

We analyzed clinicopathological data and performed whole-exome RNA sequencing on 41 TGCT samples.

Results

RNAseq analysis showed significant higher CSF1 and CSF1-R expression than a control panel of 2642 solid tumors. RNA sequencing revealed fusion transcripts in 14 patients including 6 not involving CSF1 and some previously unreported fusions. Unsupervised clustering on the expression profiles issued from this series suggested two distinct subgroups: one composed of various molecular subtypes including CSF1 and FN1 rearranged samples and one composed of four tumors harboring an HMGA2::NCOR2 fusion, suggesting distinct tumor entities. Overall, 15 patients received at least one systemic anti-CSF1R treatment and clinical improvement was observed in 11 patients, including patients from both clusters.

Discussion

This study reported molecular heterogeneity in TGCT, contrasting with the clinical and pathological homogeneity and the ubiquitous high CSF1 and CSF1R expression levels. Whether molecular diversity may impact the efficacy of systemic treatments needs to be further investigated.

Prediction of Histologic Neoadjuvant Chemotherapy Response in Osteosarcoma Using Pretherapeutic MRI Radiomics

Histologic response to chemotherapy for osteosarcoma is one of the most important prognostic factors for survival, but assessment occurs after surgery. Although tumor imaging is used for surgical planning and follow-up, it lacks predictive value. Therefore, a radiomics model was developed to predict the response to neoadjuvant chemotherapy based on pretreatment T1-weighted contrast-enhanced MRI. A total of 176 patients (median age, 20 years [range, 5-71 years]; 107 male patients) with osteosarcoma treated with neoadjuvant chemotherapy and surgery between January 2007 and December 2018 in three different centers in France (Centre Léon Bérard in Lyon, Centre Hospitalier Universitaire de Nantes in Nantes, and Hôpital Cochin in Paris) were retrospectively analyzed. Various models were trained from different configurations of the data sets. Two different methods of feature selection were tested with and without ComBat harmonization (ReliefF and t test) to select the most relevant features, and two different classifiers were used to build the models (an artificial neural network and a support vector machine). Sixteen radiomics models were built using the different combinations of feature selection and classifier applied on the various data sets. The most predictive model had an area under the receiver operating characteristic curve of 0.95, a sensitivity of 91%, and a specificity 92% in the training set; respective values in the validation set were 0.97, 91%, and 92%. In conclusion, MRI-based radiomics may be useful to stratify patients receiving neoadjuvant chemotherapy for osteosarcomas. Keywords: MRI, Skeletal-Axial, Oncology, Radiomics, Osteosarcoma, Pediatrics Supplemental material is available for this article. © RSNA, 2022.

Refining Prognosis in Localized Gastrointestinal Stromal Tumor: Clinical Significance of Phosphatase and Tensin Homolog Low Expression and Gene Loss

To investigate the use of PTEN biomarker to improve prognostic stratification in patients with localized gastrointestinal stromal tumor (GIST).

New Drug Approvals for Sarcoma in the Last 5 Years

Sarcoma and locally aggressive connective tissue tumors are a complex group of diseases with a growing number of histotypes in the most recent WHO classification. Most of these tumors are rare (incidence <6/10⁵/y) or ultrarare (<1/10⁶/y). Despite their rarity, sarcomas are often good models for the development of personalized medicine, and a large number of new clinical trials in select histotypes and molecular subsets were reported during the past 5 years, leading to a faster rate of new drug approvals. We analyzed the published literature and the abstracts reported in major congresses dedicated to sarcoma and connective tissue tumor management in the last 5 years. Several targeted therapies, cytotoxic treatments, and immunotherapies have demonstrated activity in dedicated histologic and molecular subtypes of sarcomas. The majority of the studies for ultrarare entities are uncontrolled studies, as a consequence of the rarity of histotypes, but randomized controlled trials were available in the less rare histotypes. Most successful trials were based on biomarker selection, which were often driver molecular alterations, while a large number of ongoing research programs aim to identify biomarkers in parallel to new drug development. Availability of the new agents varies across countries. This article describes the new drugs that made it through to the finish line and new agents with promising activity that are in later stages of investigation in the large family of malignant connective tissue tumors.

Systemic treatment of advanced clear cell sarcoma: results from a retrospective international series from the World Sarcoma Network

Background

Clear cell sarcoma (CCS) is a translocated aggressive malignancy with a high incidence of metastases and poor prognosis. There are few studies describing the activity of systemic therapy in CCS. We report a multi-institutional retrospective study of the outcomes of patients with advanced CCS treated with systemic therapy within the World Sarcoma Network (WSN).

Materials and methods

Patients with molecularly confirmed locally advanced or metastatic CCS treated with systemic therapy from June 1985 to May 2021 were included. Baseline demographic and treatment information, including response by Response Evaluation Criteria in Solid Tumours (RECIST) 1.1, was retrospectively collected by local investigators. Descriptive statistics were carried out.

Results

Fifty-five patients from 10 institutions were included. At diagnosis, the median age was 30 (15-73) years and 24% (n = 13/55) had metastatic disease. The median age at diagnosis was 30 (15-73) years. Most primary tumours were at aponeurosis (n = 9/55, 16%) or non-aponeurosis limb sites (n = 17/55, 31%). The most common fusion was EWSR1–ATF1 (n = 24/55, 44%). The median number of systemic therapies was 1 (range 1-7). The best response rate was seen for patients treated with sunitinib (30%, n = 3/10), with a median progression-free survival of 4 [95% confidence interval (CI) 1-7] months. The median overall survival for patients with advanced/metastatic disease was 15 months (95% CI 3-27 months).

Conclusions

Soft tissue sarcoma-type systemic therapies have limited benefit in advanced CCS and response rate was poor. International, multicentre prospective translational studies are required to identify new treatments for this ultra-rare subtype, and access to early clinical trial enrolment remains key for patients with CCS.

•

This is the largest reported series of advanced CCS patients treated with systemic therapy.

•

The activity of sarcoma-type systemic therapy is poor and modest responses were seen only with sunitinib.

•

Effective therapies are needed to improve outcomes for patients with this ultra-rare sarcoma type.

ETMR-03. Intra- and extra-cranial BCOR-ITD tumours are separate entities within the BCOR-rearranged family

BCOR-ITD tumours form an emerging family of aggressive entities with an internal tandem duplication (ITD) in the last exon of the BCOR gene. The family includes cerebral tumours, termed central nervous system BCOR-ITD (CNS BCOR-ITD), and sarcomatous types described in the kidney as clear cell sarcoma of the kidney (CCSK), in the endometrium as high-grade endometrial stromal sarcoma (HG-ESS), in bone, and in soft tissue as undifferentiated round cell sarcoma (URCS) or primitive myxoid mesenchymal tumour of infancy (PMMTI). Based on a series of 33 retrospective cases, including 10 CNS BCOR-ITD and 23 BCOR-ITD sarcomas, we interrogated the homogeneity of the entity regarding clinical, radiological and histopathological findings, and molecular signatures. Whole transcriptomic sequencing and DNA methylation profiling were used for unsupervised clustering. Histopathological review revealed marked differences between CNS BCOR-ITD and BCOR-ITD sarcomas. These two groups were consistently segregated by unsupervised clustering of expression (n=22) and DNA methylation (n=21) data. Proximity between the two groups may result from common somatic changes within key pathways directly related to the novel activity of the ITD itself. Conversely, comparison of gene signatures with single-cell RNAseq atlases suggests that the distinction between BCOR-ITD sarcomas and CNS BCOR-ITD may result from differences in cells of origin.

Increasing targeted therapy options for patients with relapsed cancer with broader somatic gene panel analysis from the primary tumor: The Profiler02 randomized phase II trial

3130

Background: PROFILER-02 is a multicenter randomized prospective study comparing the proportion of metastatic cancer patients (pts) with Targeted Agent (TA) recommendation provided by large NGS panel (FOne panel, 324 genes) vs home 87-gene NGS panel (CTRL) (PMID 30865223). Methods: Adult pts with advanced/metastatic cancer during 1st or 2nd line of therapy without known targetable gene alteration were eligible and randomized (1:1) to FOne vs CTRL panel. Both panels were performed for each patient. The randomization arm defined the first panel reviewed by dedicated Molecular Tumor Board (MTB) at disease progression while the 2nd panel remained blinded. The primary objective was the pts rate with at least one TA recommendation by the MTB using either FOne or CTRL panel. The study was designed in order to detect difference in proportions of 10% between the two panels. A sample size of 289 pts with both panels were requested to show this difference with an expected proportion of discordant pairs of 20% using a McNemar's test with 98% power and 5% two-sided significance level. Secondary endpoints included number of pts receiving at least one TA, progression free survival (PFS) and overall survival (OS). Results: From June 2017 to June 2019, among the 339 included pts 171 and 168 pts were randomized in FOne or CTRL panels’ first use, respectively. Median age was 57 years [19.0 - 85.0]; 54.9% were female. The median time from randomization to first MTB was 7.62 months [range 0.80 - 48.1]. Among the 339 pts, 147 pts (43.4%) had no TA recommendation, 108 pts (31.9%) had at least one TA recommendation according to both panels, 67 pts (19.8%) had one or more TA recommendation according to FOne panel only and 17 pts (5%) according to CTRL panel only (McNemar p < 0.001). At the time of the analysis, 51/339 (15%) pts started recommended treatment: 27 pts (8%) with TA recommendation from both panels, 21 pts (6.2%) from FOne only and 3 pts (0.3%) from CTRL only. Main initiated TA were PARP inh. (FOne n = 12; CTRL n = 9), PI3K/AKT/mTOR inh. (FOne n = 10; CTRL n = 9) and immunotherapy (ICI) (FOne n = 7; CTRL n = 0). Median PFS following first MTB were 3.2 months (95% CI 2.5-3.8) and 2.6 months (95% CI 2.0-3.8), median OS were 8.7 months (95% CI 6.6-10.8) and 8.4 months (95% CI 6.4-9.7), in the FOne and CTRL arm, respectively. Conclusions: Larger NGS panel including Tumor Mutational Burden increased the number of recommended options (TA and ICI), as well as the number of treatment initiation. Clinical trial information: NCT03163732.

PEC-PRO: A new prognostic score from a series of 93 patients with localized perivascular epithelioid cell neoplasms (PEComas) treated with curative intent

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.

REGOMAIN: A randomized, placebo-controlled, double-blinded, multicenter, comparative phase II study of the efficacy of regorafenib as maintenance treatment in patients (pts) with high-grade bone sarcomas (HGBS) at diagnosis or relapse and without complete remission after standard treatment

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.

Long-term outcomes after definitive radiotherapy with modern techniques for unresectable soft tissue sarcoma

INTRODUCTION

The use of definitive radiotherapy (dRT) in unresectable soft-tissue sarcomas (STS) is still controversial and recent data are scarce. We report clinical results of this therapeutic option.

METHODS

We retrospectively included STS patients treated between 2009 and 2020, with dRT for unresectable or with a measurable residual disease after R2 surgery. Response rate, local failure (LF), progression-free survival (PFS) and overall survival (OS) were evaluated.

RESULTS

116 patients with localized/locally advanced STS were treated from 2009 to 2020, with a median age of 71 years (range 18-92). Most tumors were deep-seated (96.6%), grade 2-3 (85.1%), located in the trunk or extremities (74.2%). Helical tomotherapy, volumetric modulated arc therapy, or stereotactic radiotherapy was performed in 39.7%, 19% and 8.6% of patients, respectively. The median equivalent dose in 2 Gy fractions (EQD2) was 60 Gy (IQR 52-65). At first follow-up, 66 (58.9%) and 25 (22%) patients had stable disease and partial response. After a median follow-up of 54.8 months (IQR 40.3-95.4), 3-year LF, PFS and OS were 43.2%, 16.6% and 34%, respectively. Median OS was 21.4 months (95%CI 14-26). The multivariate analysis identified grade 3 and AJCC T3-T4 stage to be associated with both shorter PFS and OS (all p<0.001). Macroscopically incomplete resection and EQD2 ≥64Gy were associated with better OS (p=0.016 and p=0.007). Acute and late severe adverse events occurred in 24 (19.7%) and 5 (4.3%) patients.

CONCLUSION

In unresectable STS patients, definitive modern radiotherapy is a safe and effective treatment yielding long term control in selected patients.

Intra- and extra-cranial BCOR-ITD tumours are separate entities within the BCOR-rearranged family

BCOR-ITD tumours form an emerging family of aggressive entities with an internal tandem duplication (ITD) in the last exon of the BCOR gene. The family includes cerebral tumours, termed central nervous system BCOR-ITD (CNS BCOR-ITD), and sarcomatous types described in the kidney as clear cell sarcoma of the kidney (CCSK), in the endometrium as high-grade endometrial stromal sarcoma, and in the bone and soft tissue as undifferentiated round cell sarcoma or primitive myxoid mesenchymal tumour of infancy. Based on a series of 33 retrospective cases, including 10 CNS BCOR-ITD and 23 BCOR-ITD sarcomas, we interrogated the homogeneity of the entity regarding clinical, radiological, and histopathological findings, and molecular signatures. Whole-transcriptomic sequencing and DNA methylation profiling were used for unsupervised clustering. BCOR-ITD tumours mostly affected young children with a median age at diagnosis of 2.1 years (range 0-62.4). Median overall survival was 3.9 years and progression-free survival was 1.4 years. This dismal prognosis is shared among tumours in all locations except CCSK. Histopathological review revealed marked differences between CNS BCOR-ITD and BCOR-ITD sarcomas. These two groups were consistently segregated by unsupervised clustering of expression (n = 22) and DNA methylation (n = 21) data. Proximity between the two groups may result from common somatic changes within key pathways directly related to the novel activity of the ITD itself. Conversely, comparison of gene signatures with single-cell RNA-Seq atlases suggests that the distinction between BCOR-ITD sarcomas and CNS BCOR-ITD may result from differences in cells of origin.

Reasons for acceptance and refusal of early palliative care in patients included in early-phase clinical trials in a regional comprehensive cancer centre in France: protocol for a qualitative study

INTRODUCTION

A few studies have highlighted the potential synergy between early palliative care and inclusion in an early-phase clinical trial that may improve quality of life, reduce symptoms of exhaustion related to the side effects of treatment and allow patients to complete their treatment protocol. The primary objective of this qualitative study is to evaluate the reasons for acceptance or refusal of early palliative care in patients included in early-phase clinical trials.

METHOD AND ANALYSIS

All patients from the Centre Léon Bérard (Comprehensive Cancer Centre in Lyon, France) who consent to one of the early-phase clinical trials proposed at the centre will be invited to participate in this study. The cohort will consist of a subgroup (n=20) of patients who accept palliative care together with their clinical trial, and a second subgroup (n=20) of patients who decline it. Patients will be interviewed in exploratory interviews conducted by a psychology researcher before the start of their clinical trial. The interviews will be audio-recorded. Patients will also be asked to complete quality of life and anxiety/depression questionnaires both before the beginning of the treatment and at the end of their clinical trial. The content of the interviews will be analysed thematically. Descriptive and comparative statistical analysis of both cohorts will also be conducted.

ETHICS AND DISSEMINATION

Personal data will be collected and processed in accordance with the laws and regulations in force. All patients will give informed consent to participate. This study complies with reference methodology MR004 of the Commission Nationale de l'Informatique et des Libertés. The protocol has received the validation of an ethics committee (Groupe de Réflexion Ethique du CLB, number: 2020-006). The results will be disseminated through conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT04717440.

Patterns of care and outcomes of 417 patients with METAstatic SYNovial sarcoma (METASYN): real-life data from the French Sarcoma Group (FSG)

Background

Synovial sarcoma (SS) occurs in both adult and pediatric patients. The primary aim of this study is to describe the outcomes, prognostic factors, and treatment of patients with metastatic SS within a nationwide cohort.

Patients and methods

All pediatric and adult patients with metastatic SS are registered in the French Sarcoma Group database. Data were collected from the national database https://conticabase.sarcomabcb.org/ up to March 2020. Descriptive and comparative analyses were conducted using SAS 9.4 and Stata Special Edition 16.1 software.

Results

Between January 1981 and December 2019, 417 patients with metastatic SS from 17 French sarcoma centers were included, including 64 (15.3%) under the age of 26 years. Median age was 42.5 years (range 9-87 years). The metastases were synchronous (cohort 1) or metachronous (cohort 2) in 18.9% (N = 79) and 81.1% (N = 338) patients, respectively. Median overall survival (OS) from the date of metastasis was 22.3 months (95% confidence interval 19.7-24.1 months). First-line chemotherapy without ifosfamide and/or doxorubicin was unfavorable for progression-free survival and OS (P < 0.001). Concerning cohort 1, young age, surgery of the primary tumor, and single metastatic site were independent favorable prognostic factors for OS. In cohort 2, surgery within an expert French Sarcoma Group center, absence of chemotherapy in the perioperative setting, the lungs as a single metastatic site, time to first metastasis >12 months, local therapy, and ifosfamide in the first metastatic line were independent favorable prognostic factors.

Conclusions

The outcome of patients with metastatic SS is influenced by local treatment, management in reference centers, and cytotoxic treatments given in the perioperative and metastatic setting.

•

METASYN is the largest retrospective study on metastatic adult and pediatric SS.

•

This study confirms that surgery remains the mainstay for improving OS in reference centers.

•

METASYN emphasizes the importance of focal treatment of metastases for OS.

•

This study offers real-life results in a metastatic setting and is a useful support for developing new strategies.

Wholistic approach - transcriptomic analysis and beyond using archival material for molecular diagnosis

Many neoplasms remain unclassified after histopathological examination, which requires further molecular analysis. To this regard, mesenchymal neoplasms are particularly challenging due to the combination of their rarity and the large number of subtypes, and many entities still lack robust diagnostic hallmarks. RNA transcriptomic profiles have proven to be a reliable basis for the classification of previously unclassified tumors and notably for mesenchymal neoplasms. Using exome-based RNA capture sequencing on more than 5000 samples of archival material (FFPE), the combination of expression profiles analyzes (including several clustering methods), fusion genes, and small nucleotide variations has been developed at the Centre Léon Bérard (CLB) in Lyon for the molecular diagnosis of challenging neoplasms and the discovery of new entities. The molecular basis of the technique, the protocol, and the bioinformatics algorithms used are described herein, as well as its advantages and limitations.

Trabectedin plus durvalumab in patients with advanced pretreated soft tissue sarcoma and ovarian carcinoma (TRAMUNE): an open-label, multicenter phase Ib study

PURPOSE

Trabectedin has shown pre-clinical synergy with immune-checkpoint inhibitors in pre-clinical models.

EXPERIMENTAL DESIGN

TRAMUNE is a phase Ib study investigating trabectedin combined with durvalumab trough a dose-escalation phase and two expansion cohorts (soft tissue sarcoma and ovarian carcinoma). Trabectedin was given at three dose levels (1 mg/m2, 1.2 mg/m2 and 1.5 mg/m2) on day 1, in combination with durvalumab, 1120 mg on day 2, every 3 weeks. The primary endpoints were the recommended phase II dose (RP2D) of trabectedin combined with durvalumab and the objective response rate (ORR) as per RECIST 1.1. The secondary endpoints included safety, 6-month progression-free rate (PFR), progression-free survival (PFS), overall survival, and biomarker analyses.

RESULTS

40 patients were included (dose escalation: n=9; STS cohort: n=16; ovarian cohort: n=15, 80% platinum resistant/refractory). The most frequent toxicities were grade 1-2 fatigue, nausea, neutropenia, and alanine/aspartate aminotransferase increase. One patient experienced a dose-limiting toxicity at dose level 2. Trabectedin at 1.2 mg/m2 was selected as the RP2D. In the STS cohort, 43% of patients experienced tumor shrinkage, the ORR was 7% (95% CI 0.2 - 33.9) and the 6-month PFR 28.6% (95% CI 8.4-58.1). In the ovarian carcinoma cohort, 43% of patients experienced tumor shrinkage, the ORR was 21.4% (95% CI 4.7 - 50.8) and the 6-month PFR 42.9% (95% CI 17.7 - 71.1). Baseline levels of PD-L1 expression and CD8-positive T-cell infiltrates were associated with PFS in ovarian carcinoma patients.

CONCLUSIONS

Combining trabectedin and durvalumab is manageable. Promising activity is observed in platinum-refractory ovarian carcinoma patients.

[Bispecific antibodies targeting CD3 in oncology and hematology]

Bispecific therapies targeting CD3, so-called T-cell engagers (TCE), belong to the new spectrum of anti-tumor immunotherapies stimulating T-lymphocytes. TCE are unique constructs targeting the MHC-independent CD3 epsilon subunit (CD3e) and a tumor antigen. To date, only blinatumomab have reached market agreements in lymphoid malignancies with constructs targeting CD3exCD19. Other TCE are in advances development, with promising results targeting CD20 and BSMA in lymphoma and myeloma. These successes have relaunched the development of TCE in solid tumors, bringing mixed results so far (notably in terms of tolerance). Still, TCE pave the way to new immunotherapy in tumors considered to be refractory to inhibitors of immune checkpoints such as prostate cancer or colorectal cancer.

Avapritinib Versus Regorafenib in Locally Advanced Unresectable or Metastatic GI Stromal Tumor: A Randomized, Open-Label Phase III Study

PURPOSE

Primary or secondary mutations in KIT or platelet-derived growth factor receptor alpha (PDGFRA) underlie tyrosine kinase inhibitor resistance in most GI stromal tumors (GISTs). Avapritinib selectively and potently inhibits KIT- and PDGFRA-mutant kinases. In the phase I NAVIGATOR study (NCT02508532), avapritinib showed clinical activity against PDGFRA D842V-mutant and later-line KIT-mutant GIST. VOYAGER (NCT03465722), a phase III study, evaluated efficacy and safety of avapritinib versus regorafenib as third-line or later treatment in patients with unresectable or metastatic GIST.

PATIENTS AND METHODS

VOYAGER randomly assigned patients 1:1 to avapritinib 300 mg once daily (4 weeks continuously) or regorafenib 160 mg once daily (3 weeks on and 1 week off). Primary end point was progression-free survival (PFS) by central radiology per RECIST version 1.1 modified for GIST. Secondary end points included objective response rate, overall survival, safety, disease control rate, and duration of response. Regorafenib to avapritinib crossover was permitted upon centrally confirmed disease progression.

RESULTS

Four hundred seventy-six patients were randomly assigned (avapritinib, n = 240; regorafenib, n = 236). Median PFS was not statistically different between avapritinib and regorafenib (hazard ratio, 1.25; 95% CI, 0.99 to 1.57; 4.2 v 5.6 months; P = .055). Overall survival data were immature at cutoff. Objective response rates were 17.1% and 7.2%, with durations of responses of 7.6 and 9.4 months for avapritinib and regorafenib; disease control rates were 41.7% (95% CI, 35.4 to 48.2) and 46.2% (95% CI, 39.7 to 52.8). Treatment-related adverse events (any grade, grade ≥ 3) were similar for avapritinib (92.5% and 55.2%) and regorafenib (96.2% and 57.7%).

CONCLUSION

Primary end point was not met. There was no significant difference in median PFS between avapritinib and regorafenib in patients with molecularly unselected, late-line GIST.

TP53 Mutation as a Prognostic and Predictive Marker in Sarcoma: Pooled Analysis of MOSCATO and ProfiLER Precision Medicine Trials

(1) Background: locally resected high-grade sarcomas relapse in 40% of cases. There is no prognostic or predictive genomic marker for response to peri-operative chemotherapy. (2) Methods: MOSCATO and ProfiLER are pan-tumor prospective precision medicine trials for advanced tumors. Molecular analysis in both trials comprised targeted next-generation sequencing and comparative genomic hybridization array. We investigated if molecular alterations identified in these trials in sarcomas were associated with disease-free survival (DFS) and response to anthracyclines. (3) Results: this analysis included 215 sarcomas, amongst which 53 leiomyosarcomas, 27 rhabdomyosarcomas, 20 undifferentiated pleomorphic sarcomas, and 17 liposarcomas. The most frequently altered gene was TP53 (46 mutations and eight deletions). There were 149 surgically resected localized sarcomas. Median DFS in TP53 wild type (WT), deleted, and mutated sarcomas was 16, 10, and 10 months, respectively (p = 0.028; deletions: HR = 1.55; 95% CI = 0.75-3.19; mutations: HR = 1.70; 95%CI = 1.13-2.64). In multivariate analysis, TP53 mutations remained associated with shorter DFS (p = 0.027; HR = 2.30; 95%CI = 1.10-4.82). There were 161 localized and advanced sarcomas evaluable for response to anthracyclines. Objective response rates were 35% and 55% in TP53 WT and mutated sarcomas, respectively (OR = 2.24; 95%CI = 1.01-5.03; p = 0.05). In multivariate analysis, TP53 mutations remained associated with increased response (OR = 3.24; 95%CI = 1.30-8.45; p = 0.01). (4) Conclusions: TP53 mutations are associated with shorter DFS and increased response to anthracyclines. Post-validation, these findings could assist in decision-making for peri-operative treatments.

Randomised phase 2 study comparing the efficacy and safety of the oral tyrosine kinase inhibitor nintedanib with single agent ifosfamide in patients with advanced, inoperable, metastatic soft tissue sarcoma after failure of first-line chemotherapy: EORTC-1506-STBSG "ANITA"

PURPOSE

EORTC-1506-STBSG was a prospective, multicentric, randomised, open-label phase 2 trial to assess the efficacy and safety of second-line nintedanib versus ifosfamide in patients with advanced, inoperable metastatic soft tissue sarcoma (STS). The primary end-point was progression-free survival.

PATIENTS/METHODS

Patients with a variety of STS subtypes were randomised 1:1 to nintedanib (200 mg b.i.d. p.o. until disease progression) or ifosfamide (3 g/m² i.v. days 1-3, every 21 days for ≤6 cycles). A Korn design was applied aiming to detect an improvement in median progression-free survival (mPFS) from 3 to 4.5 months (HR = 0.667). An interim look was incorporated to stop the trial for futility if <19 of the first 36 patients treated with nintedanib were progression-free at week 12.

RESULTS

At the interim analysis, among the first 36 eligible and evaluable patients randomised for nintedanib, only 13 (36%) were progression-free at week 12. The trial was closed for further accrual as per protocol. In total, 80 patients were randomised (40 per treatment group). The mPFS was 2.5 months (95% CI: 1.5-3.4) for nintedanib and 4.4 months (95% CI: 2.9-6.7) on ifosfamide (adjusted HR = 1.56 [80% CI: 1.14-2.13], p = 0.070). The median overall survival was 13.7 months (95% CI: 9.4-23.4) on nintedanib and 24.1 months (95% CI: 10.9-NE) on ifosfamide (adjusted HR = 1.65 [95%CI:0.89-3.06], p = 0.111). The clinical benefit rate for nintedanib and ifosfamide was 50% versus 62.5% (p = 0.368), respectively. Common treatment-related adverse events (all grades) were diarrhoea (35.9% of patients), fatigue (25.6%) and nausea (20.5%) for nintedanib; and fatigue (52.6%), nausea (44.7%) and vomiting, anorexia and alopecia (28.9% each) for ifosfamide.

CONCLUSION

The trial was stopped for futility. The activity of nintedanib did not warrant further exploration in non-selected, advanced STSs.

REGOSTA: A randomized, placebo-controlled, double-blinded, multicenter study evaluating the efficacy and safety of regorafenib (REGO) as maintenance therapy after first-line treatment in patients (pts) with osteosarcoma (OS) and non-osteosarcomas (non-OS) of bone (non-Ewing, non-chondrosarcomas and non-chordomas)

TPS11576

Background: Pts with OS and non-OS of bone are treated with a multimodal sequence therapy of neoadjuvant chemotherapy (CT), surgery and adjuvant CT, followed by a close surveillance until recurrence. At recurrence, the prognosis remains poor with objective response rates of 3-29%, and a median Progression-Free Survival (PFS) of less than 4 months in OS. There is a clinical need to reduce the risk of recurrence after the initial treatment sequence. The REGOBONE study reported a significant clinical benefit of regorafenib compared to placebo in patients with relapsed OS (median PFS: 16.4 versus 4.1 weeks). Methods: This multicenter trial is ongoing to study the efficacy and safety of maintenance REGO in pts > = 16 years, with complete remission after initial treatment sequence of their bone sarcoma. 168 pts will be randomly allocated in a 1:1 ratio to receive either oral REGO or its matching placebo (control arm) at a daily dose of 120mg, continuously and for a maximum of 12 months. Randomization will be stratified according to the following risk factors: metastases (mets) at diagnosis and/or poor response to neoadjuvant CT versus no mets at diagnosis and good response to neoadjuvant CT. The primary objective is to compare the efficacy (Relapse-Free Survival) between the 2 arms. The expected 3-year RFS rates are 55% in the control arm and 74.6% in the REGO arm (HR = 0.5). 66 events will provide 80% power to show significant improvement in RFS, using a 2-sided log-rank test at a 5% level. Secondary endpoints include Time to Treatment Failure, Overall Survival, Quality of Life, safety profile, and compliance to treatment. Radiological endpoints will be evaluated using the RECIST 1.1. Translational objectives will be to identify predictive biomarkers for efficacy of REGO as maintenance therapy using liquid biopsies. As of Feb 1st, 2021, 3 patients have been randomized. 15 sites of the French Sarcoma Group will participate. Clinical trial information: NCT04055220.

Dam parity and calf sex affect maternal and neonatal behaviors during the first week postpartum in stabled Maghrebi dairy camels

Currently, a trend toward the commercialization of dromedary milk associated with recent intensive rearing systems has starting worldwide which impose constraints on animals affecting their behavioral repertoires and welfare status. The aim of this study was to investigate the effects of dam parity and calf sex on parturition, neonatal, and maternal behaviors in stabled Maghrebi dairy camels (Camelus dromedarius). Thirty-six (primiparas N = 10; multiparas N = 26) periparturient females were kept under video surveillance using a digital IR camera and 24-h sessions were chosen to assess calving, maternal, and neonatal behaviors in calving pens. Duration of restlessness, process of giving birth, and expulsion of fetal membranes were assessed. After first suckling, dams and their calves were moved into an individual enclosure to assess maternal behavior at 12 h, 24 h, 48 h, 72 h, and 7d postpartum. Behavior was assessed using a camcorder for 30 min after 1 h of young separation in an adjacent enclosure. Results showed an effect of parity on the duration of the birth process which was longer for primiparous than multiparous camels (P = 0.034). During this stage, primiparous females tended to raise their tails more often (P = 0.054) and spent more time standing (P = 0.001) than multiparous camels. Neonatal behavior was affected by calf sex. Female newborns took less time to raise their heads (P = 0.041) and to stand up (P = 0.048) for the first time and were the earliest to suckle their dams (P = 0.032). Multiparous dams stood up sooner (P = 0.019) after calving and suckled their calves earlier (P = 0.043) than primiparous dams. They emitted more bleats and exhibited more sniffing during the first week postpartum than primiparas. During the first postpartum week, both primiparas and multiparas showed a decrease in the total number of bleats (P < 0.001), low-pitch bleats (P < 0.001), and high-pitch bleats (P < 0.001), in sniffing frequency (P < 0.001) and sniffing duration (P < 0.001). This is the first study to describe in detail the calving, maternal, and neonatal behaviors of dromedary camels and to show the influence of parity and calf sex. Maternal care toward the newborn calf exhibited by a high level of bleating and sniffing activities in the first 2 days suggest that they play an important role in the establishment of mother-young relationship.