Tropomyosin receptor kinases in sarcomas - of joy and despair

Progress in histology specific treatments in soft tissue sarcoma

INTRODUCTION

Soft tissue sarcomas (STS) represent a heterogenous group of rare tumors, primarily treated with surgery. Preoperative radiotherapy is often recommended for extremity high-risk STS. Neoadjuvant chemotherapy, typically based on doxorubicin with ifosfamide, has shown efficacy in limbs and trunk wall STS. Second-line chemotherapy, commonly utilized in the metastatic setting, is mostly histology-driven. Molecular targeted agents are used across various histologies, and although the use of immunotherapy in STS is still in its early stages, there is increasing interest in exploring its potential.

AREAS COVERED

This article involved an extensive recent search on PubMed. It explored the current treatment landscape for localized and metastatic STS, focusing on the combined use of radiotherapy and chemotherapy for both extremity and retroperitoneal tumors, and with a particular emphasis on the most innovative histopathology driven therapeutic approaches. Additionally, ongoing clinical trials identified via clinicaltrials.gov are included.

EXPERT OPINION

Recently there have been advancements in the treatment of STS, largely driven by the outcomes of clinical trials. However further research is imperative to comprehend the effect of chemotherapy, targeted therapy and immunotherapy in various STS, as well as to identify biomarkers able to predict which patients are most likely to benefit from these treatments.

Epigenetic determinants in soft tissue sarcomas: molecular mechanisms and therapeutic targets

INTRODUCTION

Soft tissue sarcomas are a group of rare, mesenchymal tumors characterized by dismal prognosis in advanced/metastatic stages. Knowledge of their molecular determinants is still rather limited. However, in recent years, epigenetic regulation - the modification of gene expression/function without DNA sequence variation - has emerged as a key player both in sarcomagenesis and sarcoma progression.

AREAS COVERED

Herein, we describe and review the main epigenetic mechanisms involved in chromatin remodeling and their role as disease drivers in different soft tissue sarcoma histotypes, focusing on epithelioid sarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumors. Focusing on chromatin-remodeling complexes, we provide an in-depth on the role of BAF complex alterations in these soft tissue sarcoma histotypes. In parallel, we highlight current state-of-the-art and future perspectives in the development of rational, innovative treatments leveraging on epigenetic dysregulation in soft tissue sarcomas.

EXPERT OPINION

Therapeutic options for metastatic/advanced sarcomas are to date very limited and largely represented by cytotoxic agents, with only modest results. In the continuous attempt to find novel targets and innovative, effective drugs, epigenetic mechanisms represent an emerging and promising field of research, especially for malignant peripheral nerve sheath tumors, epithelioid and synovial sarcoma.

Head and Neck Mesenchymal Tumors with Kinase Fusions: A Report of 15 Cases With Emphasis on Wide Anatomic Distribution and Diverse Histologic Appearance

Mesenchymal tumors harboring various kinase fusions were recently recognized as emerging entities mainly in the soft tissues. We herein investigate the clinicopathologic and molecular characteristics of head and neck mesenchymal tumors harboring kinase fusions. The study cohort included 15 patients with a median age of 13 years (ranging from congenital to 63 y). The kinase genes involved in descending order were NTRK1 (n=6), NTRK3 (n=5), BRAF (n=2), and 1 each with MET, and RET. The anatomic locations were broad involving all tissue planes, including skin (n=4), intraosseous (n=4), major salivary glands (n=2), sinonasal tract (n=2), soft tissue of face or neck (n=2), and oral cavity (n=1). The histologic spectrum ranged from benign to high grade, in descending order including tumors resembling malignant peripheral nerve sheath tumor (MPNST)-like, fibrosarcoma (infantile or adult-type), lipofibromatosis-like neural tumor (LPFNT), inflammatory myofibroblastic tumor-like, and a novel phenotype resembling myxoma. Perivascular hyalinization/stromal keloid-like collagen bands and staghorn vasculature were common features in MPNST-like and LPFNT-like tumors. Two tumors (1 each with NTRK1 or BRAF rearrangement) were classified as high grade. By immunohistochemistry, S100 and CD34 positivity was noted in 71% and 60%, frequently in MPNST-like and LPFNT-like phenotypes. Pan-TRK was a sensitive marker for NTRK-translocated tumors but was negative in tumor with other kinase fusions. One patient with a high-grade tumor developed distant metastasis. Molecular testing for various kinase fusions should be considered for S100+/CD34+ spindle cell neoplasms with perivascular hyalinization and staghorn vessels, as pan-TRK positivity is seen only in NTRK fusions.

[Medicinal treatment of retroperitoneal soft tissue sarcomas]

Retroperitoneal soft tissue sarcomas represent extreme challenges for interdisciplinary treatment teams. The sarcoma-specific experience of surgeons has the greatest impact on the survival of patients; however, too many patients still die despite optimal local treatment. The role of chemotherapy is undisputed only for patients with highly malignant bone sarcomas or rhabdomyosarcomas. For soft tissue sarcomas in adult patients, especially liposarcomas and leiomyosarcomas, the evidence situation is very unsatisfactory. This overview article discusses the complex data situation and controversial aspects that are relevant for current treatment decisions in interdisciplinary treatment teams.