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Detailed characterization of established STS PDX models.

Genomic profile, describing copy number gains and losses, obtained using low coverage whole genome sequencing of subsequent passages of STS PDX models, revealing a stable copy number profile throughout passaging. Copy number profile of (A) the MPNST model UZLX-STS39 and (B) the mesenchymal chondrosarcoma model UZLX-STS41.

Soft-tissue sarcomas (STS) represent a heterogeneous group of rare, malignant tumors of mesenchymal origin. Reliable in vivo sarcoma research models are scarce. We aimed to establish and characterize histologically and molecularly stable patient-derived xenograft (PDX) models from a broad variety of STS subtypes. A total of 188 fresh tumor samples from consenting patients with localized or advanced STS were transplanted subcutaneously in NMRI-nu/nu–immunodeficient mice. Once tumor growth was observed, the material was passaged to a next generation of mice. A patient-derived tumor sample was considered “successfully engrafted” whenever the sample was transplanted to passage 1. A PDX model was considered “established” when observing stable morphologic and molecular features for at least two passages. With every passage, histologic and molecular analyses were performed. Specific genomic alterations and copy-number profile were assessed by FISH and low coverage whole-genome sequencing. The tumor engraftment rate was 32% (61/188) and 188 patient samples generated a total of 32 PDX models, including seven models of myxofibrosarcoma, five dedifferentiated liposarcoma, five leiomyosarcoma, three undifferentiated pleomorphic sarcoma, two malignant peripheral nerve sheet tumor models, and single models of synovial sarcoma and some other (ultra)rare subtypes. Seventeen additional models are in early stages of engraftment (passage 1–2). Histopathologic and molecular features were compared with the original donor tumor and were stable throughout passaging. The platform is used for studies on sarcoma biology and suited for in vivo preclinical drug testing as illustrated by a number of completed and ongoing laboratory studies.

Tenosynovial giant cell tumor (TGCT) is defined by the World Health Organization (WHO) as a family of lesions most often arising from the synovium of joints, bursae and tendon sheaths. It is composed of synovial- like mononuclear cells, admixed with multinucleate giant cells, foam cells, siderophages and inflammatory cells (1). It can have various clinical manifestations, and is therefore subdivided in a diffuse and a localized/ nodular subtype. Furthermore, the lesions can have an intra- or extra-articular location. The purpose of this paper is to present the case of a 41-year-old male suffering from multifocal extra- and intra-articular TGCT of the right knee, with involvement of the pes anserinus bursa and an anterior cruciate ligament (ACL) autograft respectively. The ACL reconstruction was performed 11 years prior to the diagnosis of the TGCT, using tendons harvested from the pes anserinus. Our case illustrates the risk of transferring TGCT from an extra- to intra-articular location during ACL reconstruction, when using tendons of a pes anserinus prone to develop this condition. To our knowledge, no similar case was published in the literature so far.

Background: Synovial sarcomas (SS) are malignant mesenchymal neoplasms that account for about 10% of all sarcomas. Complete surgical excision is the mainstay of primary treatment for localized disease, but SS have a high tendency for local relapse and metastases. Metastatic disease is commonly treated with systemic chemotherapy. Methods: We designed a retrospective analysis to describe the clinical presentation, course of treatment, outcome, and prognosis of patients with SS. Univariate and multivariate analyses were performed for potential prognostic factors. Results: We identified 134 patients treated between 1987 and 2018, with a cutoff date of December 2018. Demographics, disease characteristics, treatment, and survival rates were collected and analyzed. The median overall survival (mOS) from the date of diagnosis was 96.7 months. The median progression-free survival was 6.37 months. Disease-free survival was 26 months. Age over 65 years was found to be a prognostic factor with statistically significant value in the univariate analysis regarding mOS (p = 0.015) and mOS after local relapse (p = 0.0228). Conclusions: Even though our study is limited by the retrospective nature of the analysis, it adds an important amount of clinical data regarding the treatment and outcome of SS.

Soft-tissue sarcomas (STS) represent a heterogeneous group of rare, malignant tumors of mesenchymal origin. Reliable in vivo sarcoma research models are scarce. We aimed to establish and characterize histologically and molecularly stable patient-derived xenograft (PDX) models from a broad variety of STS subtypes. A total of 188 fresh tumor samples from consenting patients with localized or advanced STS were transplanted subcutaneously in NMRI-nu/nu-immunodeficient mice. Once tumor growth was observed, the material was passaged to a next generation of mice. A patient-derived tumor sample was considered "successfully engrafted" whenever the sample was transplanted to passage 1. A PDX model was considered "established" when observing stable morphologic and molecular features for at least two passages. With every passage, histologic and molecular analyses were performed. Specific genomic alterations and copy-number profile were assessed by FISH and low coverage whole-genome sequencing. The tumor engraftment rate was 32% (61/188) and 188 patient samples generated a total of 32 PDX models, including seven models of myxofibrosarcoma, five dedifferentiated liposarcoma, five leiomyosarcoma, three undifferentiated pleomorphic sarcoma, two malignant peripheral nerve sheet tumor models, and single models of synovial sarcoma and some other (ultra)rare subtypes. Seventeen additional models are in early stages of engraftment (passage 1-2). Histopathologic and molecular features were compared with the original donor tumor and were stable throughout passaging. The platform is used for studies on sarcoma biology and suited for in vivo preclinical drug testing as illustrated by a number of completed and ongoing laboratory studies. ispartof: MOLECULAR CANCER THERAPEUTICS vol:18 issue:6 pages:1168-1178 ispartof: location:United States status: published

STS constitutes a family of rare mesenchymal tumors with more than 70 subtypes described. The limited treatment options available for advanced STS patients underline the need for reliable preclinical models to test new therapeutic approaches. We established a panel of PDX models (XenoSarc) by subcutaneous implantation of fresh tumor specimens in athymic mice (nu/nu NRMI). Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of animals. At each passage tumor fragments were collected for histopathological and molecular characterization. In an ongoing effort 493 STS samples from 414 consenting patients treated at the University Hospitals, Leuven (Belgium) have been transplanted. A total of 67 PDX models from 20 STS subtypes have been established, meaning they have stable morphological, immunohistochemical and genetic characteristics over at least 2 passages. The PDX platform includes more common STS subtypes such as myxofibrosarcoma (n=12 models), gastrointestinal stromal tumors (9), dedifferentiated liposarcoma (10), and leiomyosarcoma (8), as well as models from ultra-rare subtypes, e.g. pulmonary intimal sarcoma, extraskeletal osteosarcoma, mesenchymal chondrosarcoma, myxoinflammatory fibroblastic sarcoma and others. All relevant details about the donor patient and tumor characteristics, including sensitivity to the standard treatments, are known for every model. The models are well-characterized, with availability of molecular information on genomic profile (by low-coverage whole genome sequencing), and expression profile (by RNA sequencing). Xenografts are accompanied by ready to use tissue microarrays (TMA) from the models, which can be exploited for target identification and model selection for preclinical studies. Ex-mouse material can also be used to establish primary cell cultures and 3D organoids for in vitro screening purposes. The XenoSarc platform offers opportunities for studying the biology of various sarcoma subtypes including ultra-rare entities and was found to be a very reliable tool for early drug screening in STS in preparation of clinical testing of novel compounds. The platform is available for collaborative preclinical projects with academic and industrial partners. Citation Format: Agnieszka Wozniak, Luna De Sutter, Lore De Cock, Britt Van Renterghem, Che-Jui Lee, Yannick Wang, Ulla Vanleeuw, Kimberly Verbeeck, Daphne Hompes, Friedl Sinnaeve, Hazem Wafa, Baki Topal, Joris Jaekers, Dirk Van Raemdonck, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. XenoSarc: patient-derived xenograft (PDX) models of soft tissue sarcoma (STS) and their histopathological and molecular characterization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3100.

Intraosseous schwannomas represent an extremely rare subgroup of schwannomas, accounting for

Osteochondrolipomas, a very rare combination of chondroid and osseous differentiation within lipomas, are typically found in the neck and head area. We present the case of an osteochondrolipoma in the thigh of a 54-year-old female, with matching histological and cytological correlation. To the best of our knowledge, this atypical location has only been reported once in the literature.

Background. Solitary fibrous tumor (SFT) is a rare variant of soft tissue sarcoma (STS). Materials and Methods. We reviewed SFT patients (pts) treated at our institution between 12/1990 and 09/2017. Results. We identified 94 pts with a median follow-up (mFU) of 4.7 years (range: 0.1–21.53). Primary sites were the chest (33%), abdomen (21.3%), brain (12.8%), and extremities (9.6%); 6.4% of pts presented with synchronous metastasis. Median overall survival (mOS) from the first diagnosis was 56.0 months (m) (0.3–258.3). Doege–Potter syndrome was seen in 2.1% of pts. Primary resection was performed in 86 pts (91.5%). Median progression-free survival was 34.1 m (1.0–157.1), and 43% of pts stayed SFT-free during FU. Local recurrence occurred in 26.7% after a mFU of 35.5 m (1.0–153.8), associated with an OS of 45.1 m (4.7–118.2). Metachronous metastasis occurred in 30.2% after a mFU of 36.0 m (0.1–157.1). OS in metastatic pts was 19.0 m (0.3–149.0). Systemic therapy was given to 26 pts (27.7%) with inoperable/metastatic disease. The most common (57.7%) upfront therapy was doxorubicin, achieving responses in 13.3% of pts with a PFS of 4.8 m (0.4–23.8). In second line, pts were treated with ifosfamide or pazopanib, the latter achieving the highest response rates. Third-line treatment was heterogeneous. Conclusion. SFT is an orphan malignancy with a highly variable clinical course and a considerable risk of local failure and metachronous metastasis. Surgery is the only curative option; palliative systemic therapy is used in inoperable/metastatic cases but achieves low response rates. The highest response rates are seen with pazopanib in second/third line.

Epidermolysis bullosa dystrophica is a rare dermatological disease characterized by extreme skin fragility and elevated risk of developing a squamous cell carcinoma. In some cases, amputation of a limb is necessary. Case description and methods: A 37-year-old man with recessive, severe generalized epidermolysis bullosa dystrophica developed a squamous cell carcinoma on the right forearm requiring a below-elbow amputation. Preoperative advice concerning indication and level of amputation was given. Due to potential skin problems, a conventional prosthesis was not feasible. Findings and outcomes: A custom-designed adaptive prosthesis with an upper arm cuff was trialed and was well tolerated. Multiple working tools, attached with a rotation and inclination system, allowed independence and return to work.Despite multiple potential skin problems of the stump, the patient was successfully fitted with a custom-designed adaptive prosthesis. Preparation for this fitting was done by a comprehensive multidisciplinary patient-centered approach. Clinical relevance Despite severe skin fragility, a patient with epidermolysis bullosa dystrophica was successfully fitted with a custom-designed adaptive upper limb prosthesis allowing good functional outcome. This required a multidisciplinary and patient-centered approach.

Aim: Osteosarcoma patients receive high doses of methotrexate (MTX). However, pharmacogenetic information remains limited and has mainly been investigated in leukemia so far. Patients & methods: We investigated the link between the MTHFR C677T genotype, toxicity levels (mucositis, MTX plasma level, hematological toxicity and hepatotoxicity) and survival of 48 pediatric osteosarcoma patients. Results: The TT genotype did not show more toxicity compared with the CC/CT genotype. However, plasma MTX levels were related with mucositis, but not with hematological toxicity, nor hepatotoxicity. Survival rates did not differ between homozygous and non-homozygous patients. Yet, homozygous patients had higher relapse risk. Conclusion: The MTHFR C667T polymorphism is not predictive for toxicity or overall survival, but could be used for relapse risk stratification.

Background: STS constitutes a rare family of mesenchymal tumors with more than 70 subtypes classified by WHO (2013). The limited treatment options available for advanced STS underline the need for reliable preclinical models, especially from ultra-rare subtypes, to test novel therapeutic strategies. Methods: A panel of PDX models was established by subcutaneous implantation of fresh tumor specimens in immunodeficient, athymic nude NMRI mice. Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of mice. At each passage tumor fragments were collected for histopathological and molecular characterization. A model was considered “established” after observing stable histological and molecular features for at least two passages. Furthermore, ex-mouse tumor tissue samples were stored, further characterized by immunocytology and flow cytometry and cultured to be used for in vitro drug testing. Results: Between September 2011 and November 2019, 375 STS samples from 325 consenting patients treated at the University Hospitals, Leuven, Belgium have been transplanted. A total of 56 PDX models were established, maintaining the histopathological and molecular features of the original tumor. Detailed clinical information about the donor patient and tumor characteristics (including sensitivity to standard and experimental agents), is known for every model. At present the XenoSarc platform includes ready to use models of dedifferentiated liposarcoma (11 models), gastrointestinal stromal tumor (8), myxofibrosarcoma (8), leiomyosarcoma (7), malignant peripheral nerve sheath tumor (3), synovial sarcoma (2), pulmonary artery intimal sarcoma (2), epithelioid hemangioendothelioma (1), mesenchymal chondrosarcoma (1), pleomorphic rhabdomyosarcoma (1), CIC-rearranged round cell sarcoma (1), myxoinflammatory fibroblastic sarcoma (1), rhabdomyosarcoma not otherwise specified (NOS) (1), telangiectatic extraskeletal osteosarcoma (1), extraskeletal osteosarcoma (1) and high-grade undifferentiated pleomorphic sarcoma (7). These models are well-characterized, including molecular information on copy number changes (by low-coverage whole genome sequencing), gene expression profile (by RNA-Seq) and targeted sequencing to detect mutations in genes involved in tumorigenesis. In addition, we have constructed tissue microarrays (TMA) from the xenografts which are used for target identification and model selection for preclinical studies. We are using the xenografts for in vivo testing of novel agents, including targeted and cytotoxic (pro-)drugs, and results already served as rationale for a number of prospective clinical trials. A total of 27 other xenografts are still in early stages of engraftment, not yet fulfilling our criteria of an “established” model. Conclusion: The XenoSarc platform offers a lot of opportunities for studying the biology of a variety of important sarcoma subtypes including ultra-rare entities, and has proven efficiency for early drug screening in STS in preparation of clinical testing of novel compounds. The platform is well maintained and continuously expanded, and available to collaborators from academia and industry. Citation Format: Agnieszka Wozniak, Britt Van Renterghem, Jasmien Cornillie, Yannick Wang, Che-Jui Lee, Jasmien Wellens, Ulla Vanleeuw, Madita Nysen, Daphne Hompes, Friedl Sinnaeve, Hazem Wafa, Baki Topal, Tom Verbelen, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. XenoSarc: Patient-derived xenograft (PDX) models of soft tissue sarcoma (STS) and their histopathological and molecular characterization [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1117.

The treatment of Ewing sarcoma (ES) in adult patients requires a multidisciplinary approach. Systemic therapy remains an important component of clinical management of this disease. ES is extremely rare in adult patients. Due to the rarity of the disease, no standard of care in terms of chemotherapy for the adult population exists, and the level of evidence for individual agents or some multidrug combinations is limited. Most regimens that are used in both adults and children include anthracyclines, etoposide, vincristine, cyclophosphamide, and ifosfamide. In this report, we describe our experience with the alternating use of triple combination therapies based on vincristine, ifosfamide, and doxorubicin (VIA) and an etoposide, ifosfamide, and cisplatin combination (VIP). We retrospectively evaluated the response rates, outcome, and tolerance of adult patients ( = 64) treated with VIA/VIP between 1990 and 2014. The patients included were treated with perioperative chemotherapy (53.1% neoadjuvant therapy and 17.2% adjuvant therapy) or had synchronous metastases at diagnosis (29.7%). Five-year overall survival rate was 52.2% for all patients, 72.2% for patients with localized disease, and 5.3% in patients with synchronous metastases. Overall response rate (ORR) was 37% after 2 cycles of VIA and 2 cycles of VIP. There were no patients with progressive disease (PD). ispartof: Sarcoma vol:2017 pages:1781087- ispartof: location:Egypt status: published

We report the case of a young woman with recurrent unilateral hip pain. A polylobular cystic mass was found in the right adductor space. Magnetic resonance imaging (MRI) revealed a polynodular mass migrating from the intrapelvic region along the obturator nerve. Because of a history of cyclic pain and the characteristics on MRI (hypointense rim and spots of spontaneous hyperintense signal on T1-weighted images), an endometrioma was suspected. The diagnosis of endometriosis was later confirmed through ultrasound-guided biopsy.

Background: STS constitutes a rare family of mesenchymal tumors with more than 70 subtypes described. The limited treatment options available for advanced STS underline the need for reliable preclinical models to test novel therapeutic strategies. Methods: Panel of PDX models was established by subcutaneous implantation of fresh tumor specimens in immunodeficient, athymic nude NMRI mice. Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of animals. At each passage tumor fragments were collected for detailed characterization. A model was considered established after observing stable histological and molecular features for at least two passages. Results: Between 09/2011 and 11/2017, 228 STS samples from 203 consenting patients treated at University Hospitals Leuven, Belgium, have been transplanted. Thirty-three stable PDX models have been established, maintaining the histopathological and molecular features of the original tumor. Detailed clinical information about a donor patient, including sensitivity to given therapy, is linked to every model. Higher engraftment rate was observed in samples collected from patients who developed metastasis throughout the course of disease (38% vs. 23%, p Conclusion: Our XenoSarc platform contains a number of well-annotated models, characterized by stable histological and molecular features. This platform is a reliable tool for the evaluation of new anticancer treatments for STS and for studying the biology of these rare diseases. The platform is made available to collaborators from academia and industry. Citation Format: Agnieszka Wozniak, Jasmien Cornillie, Yemarshet K. Gebreyohannes, Yannick Wang, Jasmien Wellens, Ulla Vanleeuw, Daphne Hompes, Marguerite Stas, Friedl Sinnaeve, Hazem Wafa, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. XenoSarc: Patient-derived xenograft (PDX) models of soft tissue sarcoma (STS)—an update on a preclinical platform for early drug testing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1031.

Background: STS constitutes a rare and very heterogeneous family of mesenchymal tumors. The limited treatment options available for advanced STS underline the need for reliable preclinical models to test novel therapeutic strategies. Methods: A panel of patient-derived xenografts (PDX) was established by subcutaneous implantation of fresh, surgically resected or biopsied tumor specimens in immunodeficient, athymic nude NMRI mice. Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of mice. At each passage tumor fragments were collected for histopathological and molecular characterization. A model was considered established after observing stable histological and molecular features for at least two passages. Results: Until now 171 STS samples from consenting patients treated at the University Hospitals, Leuven, Belgium, have been transplanted. Twenty-eight well-characterized, stable PDX models of STS have been established, maintaining the histopathological and molecular features of the original tumor. The detailed clinical information about a donor patient, including sensitivity to standard and experimental drugs, is linked to every model. At this point the XenoSarc platform includes models of gastrointestinal stromal tumor (6 models), myxofibrosarcoma (6), dedifferentiated liposarcoma (3), malignant peripheral nerve sheath tumor (3), synovial sarcoma (1), leiomyosarcoma (4), epithelioid haemangioendothelioma (1), mesenchymal chondrosarcoma (1), pleomorphic rhabdomyosarcoma (1) and high-grade undifferentiated pleomorphic sarcoma (2). From these models we have also available tissue microarray (TMA) as well as data on genomic and/or expression profile including mutations (by RNA-Seq). Some of these models have already been successfully used for in vivo testing of novel agents, including both targeted and cytotoxic (pro-)drugs, and results served as a rationale for several prospective clinical trials. In addition, 24 other xenografts are still in early stages of engraftment, not yet fulfilling our criteria of an “established model”. Conclusion: Our XenoSarc platform contains a number of well-annotated models, characterized by stable histological and molecular features. This platform is a reliable tool for the evaluation of new anticancer treatments for STS and for studying the biology of these rare diseases. The platform is made available to collaborators from academia and industry. Citation Format: Agnieszka Wozniak, Jasmien Cornillie, Yemarshet K. Gebreyohannes, Jasmien Wellens, Lise Vreys, Daphne Hompes, Marguerite Stas, Friedl Sinnaeve, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. XenoSarc: Patient-derived xenograft (PDX) models of soft tissue sarcoma (STS), an update on a preclinical platform for early drug testing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4811. doi:10.1158/1538-7445.AM2017-4811

Background: STS constitutes a rare and very heterogeneous family of mesenchymal tumors. The limited treatment options available for advanced STS underline the need for reliable preclinical models to test novel therapeutic strategies. Methods: A panel of patient-derived xenografts (PDX) was established by subcutaneous implantation of fresh, surgically resected tumor specimens in immunodeficient athymic nude NMRI mice. Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of mice. At each passage tumor fragments were collected for histolopathological and molecular characterization. A model was considered established after observing stable histological and molecular features for at least two passages. To evaluate the stability of the genomic profile we performed low-coverage whole-genome sequencing on DNA isolated from tumors obtained from at least two passages. In addition RNA-seq was used to better characterize the mutational profile of the ex-mouse tumors. Results: Until now 139 STS samples from consenting patients treated at the University Hospitals, Leuven, Belgium, have been transplanted. Twenty six well-characterized, stable STS PDX models have been established, maintaining the histopathological and molecular features of the original tumor. Seventeen models, analyzed with low-coverage DNA sequencing, showed a stable genomic profile in at least two different tumor passages. At this point the panel includes models of gastrointestinal stromal tumor (6 models), myxofibrosarcoma (5), dedifferentiated liposarcoma (3), malignant peripheral nerve sheath tumor (3), synovial sarcoma (2), leiomyosarcoma (3) epithelioid haemangioendothelioma (1), mesenchymal chondrosarcoma (1) and undifferentiated high grade sarcoma (2). Some of these models have already been successfully used for in vivo testing of novel agents, including both targeted and cytotoxic (pro-)drugs, and results served as a rationale for at least four prospective clinical trials. In addition 22 other xenografts are still in early stages of engraftment, not yet fulfilling our criteria of an “established model”. Conclusion: Our panel of mesenchymal PDX models is characterized by stable histological and molecular features. These clinically well-annotated models can contribute to reliable preclinical studies for new anticancer treatments for STS. The availability of unique, rare STS xenografts also allows to study the biology of these diseases. The platform is made available to collaborators from academia and industry. Citation Format: Agnieszka Wozniak, Jasmien Cornillie, Yemarshet K. Gebreyohannes, Bram Boeckx, Haifu Li, Thomas Van Looy, Giuseppe Floris, Jasmien Wellens, Lise Vreys, Daphne Hompes, Marguerite Stas, Friedl Sinnaeve, Diether Lambrechts, Maria Debiec-Rychter, Raf Sciot, Patrick Schoffski. Patient-derived xenograft (PDX) models of soft tissue sarcoma (STS): a preclinical platform for early drug testing. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5197.

A retrospective review was conducted in 28 patients (31 feet) with recalcitrant infero-medial heel pain, to assess the clinical outcome of a combined release of the first branch of the lateral plantar nerve and the plantar fascia. All patients were questioned by telephone interview on their pre- versus post-operative level of pain and function (based on the Kitaoka mid-foot scale and the visual analog scale), and their satisfaction with the result of the intervention. Limitations of functional activity decreased, maximum walking distance increased and the level of pain decreased from 8.9 to 1.4 on the visual analog scale. The majority of patients was satisfied with the surgery (90.3%) and would undergo the same procedure again or would recommend it (92.9%). While conservative management remains the gold standard for treatment of infero-medial heel pain and/or plantar fasciitis, patients with recalcitrant disease usually can be effectively treated surgically with a combined release of the plantar fascia and the first branch of the lateral plantar nerve.

Background: STS constitutes a rare and very heterogeneous family of tumors of mesenchymal origin. The limited treatment options available for advanced STS underline the need for reliable preclinical models to test novel therapeutic strategies. Methods: A panel of patient-derived xenografts was established and is currently expanded in nu/nu NMRI mice by subcutaneous implantation of fresh, surgically resected tumor specimens from consenting patients with STS, treated at the University Hospitals Leuven, Belgium. We mainly focused on STS subtypes which harbor specific genetic alterations (e.g. translocations, gene amplifications). Once tumor growth was observed, pieces of tissue were re-transplanted to the next generation of mice. At each passage tumor fragments were collected for histological and molecular characterization. Fluorescence in situ hybridization (FISH) was performed to confirm specific genomic alterations in selected xenografts. A STS xenograft model was considered established after observing maintained histological and molecular features for at least two passages. Results: Until now a total of 78 STS patient samples have been transplanted. Fifteen well-characterized, stable STS models have already been established, maintaining the features of the original tumor: myxofibrosarcoma (4 models), dedifferentiated liposarcoma (2), synovial sarcoma (2), epithelioid haemangioendothelioma (1), malignant peripheral nerve sheath tumor (2), mesenchymal chondrosarcoma (1), leiomyosarcoma (2) and sarcoma not otherwise specified (1). Some of these models have already been successfully used for in vivo testing of novel agents, including tyrosine kinase inhibitors or cytotoxic (pro-)drugs. Twelve other xenografts are still in early stages of engraftment, not yet fulfilling our criteria of “established model”. Conclusion: This newly established, representative panel of STS xenografts is characterized by stable histological and molecular features reflecting the pheno- and genotype of the original patient samples. This panel is thus well suited for in vivo drug testing of innovative agents. The unique availability of models of some ultra-rare entities will also allow us to study the biology of these diseases. The platform is available for collaboration with academic and commercial partners (contact patrick.schoffski@uzleuven.be). Citation Format: Haifu Li, Jasmien Cornillie, Agnieszka Wozniak, Thomas Van Looy, Yemarshet Gebreyohannes, Jasmien Wellens, Ulla Vanleeuw, Daphne Hompes, Marguerite Stas, Friedl Sinnaeve, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. Establishment and characterization of a panel of patient-derived soft tissue sarcoma (STS) xenograft models for in vivo testing of novel therapeutic approaches. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1460. doi:10.1158/1538-7445.AM2015-1460

Aim: STS constitutes a rare, heterogeneous family of tumours of mesenchymal origin. The limited treatment options available for advanced STS underline the need for reliable preclinical models to test novel therapeutic strategies. Methods: Patient-derived xenografts were established in nu/nu NMRI mice by subcutaneous implantation of fresh, surgically resected tumour specimens from consenting patients with STS treated at University Hospitals Leuven. We mainly focused on STS subtypes which harbour specific genetic alterations (e.g. translocations, gene amplifications). Once tumour growth was observed, pieces of tumour were re-transplanted to a next generation of mice. At each passage tumour fragments were collected for histological and molecular characterization. Specific genomic alterations were confirmed in subsequent passages by fluorescence in situ hybridization. A STS xenograft model was considered to be established after observing stable histological and molecular features for at least two passages. Results: Until now we have transplanted a total of 65 patient-derived STS samples. We were able to successfully establish 12 well-characterized STS models maintaining the features of the original tumour: myxofibrosarcoma (3 models); dedifferentiated liposarcoma (2); synovial sarcoma (2); epithelioid haemangioendothelioma (1); malignant peripheral nerve sheath tumour (1); mesenchymal chondrosarcoma (1); leiomyosarcoma (1) and sarcoma not otherwise specified (1). Some of these models have already been successfully used for in vivo testing of novel agents including tyrosine kinase inhibitors or cytotoxic prodrugs. In addition, 12 other xenografts are still in early stages of engraftment, not yet fulfilling our criteria of “established model”. Conclusions: Our newly established STS xenografts maintain the histological and molecular characteristics of the original patient sample, therefore offering a promising preclinical platform for testing anti-cancer drugs. The availability of models of some ultra-rare entities would also allow us to study the biology of these diseases. Disclosure: All authors have declared no conflicts of interest.