Malignant peripheral nerve sheath tumor (MPNST), an aggressive soft-tissue sarcoma, occurs in people with neurofibromatosis type 1 (NF1) and sporadically. Whole-genome and multi-regional exome sequencing, transcriptomic, and methylation profiling of 95 tumor samples revealed the order of genomic events in tumor evolution. Following biallelic inactivation of NF1, loss of CDKN2A or TP53 with or without inactivation of polycomb repressive complex 2 (PRC2) leads to extensive somatic copy number aberrations (SCNAs). Distinct pathways of tumor evolution are associated with inactivation of PRC2 genes and H3K27 trimethylation (H3K27me3) status. Tumors with H3K27me3 loss evolve through extensive chromosomal losses followed by whole genome doubling and chromosome 8 amplification, and show lower levels of immune cell infiltration. Retention of H3K27me3 leads to extensive genomic instability, but an immune cell-rich phenotype. Specific SCNAs detected in both tumor samples and cell-free DNA (cfDNA) act as a surrogate for H3K27me3 loss and immune infiltration, and predict prognosis.
Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are aggressive soft tissue sarcomas that can occur sporadically or in the setting of the Neurofibromatosis type 1 (NF1) cancer predisposition syndrome. These tumors carry a dismal overall survival. Previous work in our lab had identified ATRX chromatin remodeler (ATRX), previously termed, Alpha Thalassemia/Mental Retardation Syndrome X Linked as a gene mutated in a subset of MPNSTs. Given the great need for novel biomarkers and therapeutic targets for MPNSTs, we sought to determine the expression of ATRX in a larger subset of sporadic and NF1 associated MPNSTs (NF1-MPNSTs). We performed immunohistochemistry (IHC) on 74 MPNSTs (43 NF1-associated and 31 sporadic), 21 plexiform neurofibromas, and 9 atypical neurofibromas. Using this approach, we have demonstrated that 58% (43/74) of MPNSTs have aberrant ATRX expression (<80% nuclear expression) compared to only 7% (2/30) of benign (plexiform and atypical) neurofibromas. Second, we demonstrated that 65% (28/43) of NF1-MPNSTs displayed aberrant ATRX expression as did 48% (15/31) of sporadic MPNSTs. Finally, we show that aberrant ATRX expression was associated with a significantly decreased overall survival for patients with NF1-MPNST (median OS of 17.9 months for aberrant expression and median OS not met (>120 months) for intact expression, p = 0.0276). In summary, we demonstrate that ATRX is aberrantly expressed in the majority of NF1-MPNSTs, but not plexiform or atypical neurofibromas. Additionally, aberrant ATRX expression is associated with decreased overall survival in NF1-MPNST, but not sporadic MPNST and may serve as a prognostic marker for patients with NF1-MPNST.
Background: Cytotoxic chemotherapy remains the standard of care first-line treatment for advanced and metastatic soft-tissue sarcomas (STSs). Certain patients may not be chemotherapy candidates based upon age or co-morbidities, leaving limited treatment options. Pazopanib is a multi-targeted tyrosine kinase inhibitor that is FDA-approved for metastatic STS after the first line. We proposed a phase II study evaluating pazopanib as a first-line agent in patients with advanced disease who are deemed not to be candidates for chemotherapy. Methods: Eligible patients were at least 18 years old, not candidates for chemotherapyand were treatment naive. Pazopanib was titrated from 200 mg twice daily to a goal of 800 mg
The emergence of immunotherapy as a cancer therapy has dramatically changed the treatment paradigm of systemic cancer therapy. There have been several trials evaluating immune checkpoint blockade (ICI) in soft tissue sarcoma. While there is generally a limited response in sarcoma, a subset of patients has durable responses to immunotherapy. This is attributable to a variety of factors including histologic subtype, tumor-infiltrating lymphocytes, and the tumor microenvironment among others. There is ongoing translational and clinical research evaluating ICI resistance in sarcoma and identifying therapeutic strategies to overcome this resistance. Herein, we provide a review of the current data, proposed mechanisms of resistance, and potential approaches to overcome this resistance.
TPS11583 Background: Soft tissue sarcomas (STS) are rare malignancies with poor prognosis in the metastatic setting. Current standard therapy includes anthracycline based chemotherapy. Cabozantinib is a multikinase inhibitor that has demonstrated efficacy in solid tumors such as renal cell carcinoma (RCC) and hepatocellular carcinoma (HCC). A phase II study of cabozantinib in advanced STS is underway. Cabozantinib in combination with immune checkpoint blockade has shown clinical benefit in several tumor types including HCC, RCC, non-small cell lung cancer, and urothelial carcinoma. Since cabozantinib may alter PD-1 expression in regulatory T-cells and promote an immune permissive environment, we hypothesize that combining cabozantinib with immune checkpoint inhibition is a therapeutic strategy that will be more effective than cabozantinib alone. Additionally, the design of the trial will allow assessment of whether pretreatment with cabozantinib will enhance the efficacy of nivolumab and ipilimumab alone. Methods: This is an open label, multicenter, randomized phase II clinical trial of cabozantinib (60mg orally daily as a single agent, 40mg in combination) with or without combination Ipilimumab (ipi, 1mg/kg IV every 3 weeks for 4 doses) and Nivolumab (nivo, 3mg/kg IV every 3 weeks for four doses, then 480mg IV every 4 weeks) in patients (pts) with unresectable or metastatic STS refractory to up to two lines of chemotherapy. 105 pts with non-translocation driven sarcomas will be enrolled at three US sites and randomized 2:1 to the combination group. Pts will be stratified by prior pazopanib use and balanced for histologies. Patients who progress on arm A will cross over to combination therapy (arm B). The primary efficacy endpoint is objective response rate (ORR) by RECIST 1.1. 35 patients in Cohort A (cabozantinib alone) and 70 patients in Cohort B (cabozantinib plus ipi/nivo) will be required to detect an increase of the ORR from 10% in cohort A to 30% in cohort B with 81% power with a one-sided alpha level of 10%. Key eligibility criteria include: at least 18 years of age, ECOG performance status of 0 or 1, ≤2 prior lines of therapy and measurable disease. Exclusion criteria include: translocation-driven sarcoma except alveolar soft part sarcoma (ASPS), prior immunotherapy, and chronic use of corticosteroids or other immunosuppression. Secondary endpoints are safety, overall and progression free survival, disease control rate, and response rate to ipilimumab and nivolumab after cabozantinib pretreatment. Mandatory tumor biopsies pre-treatment and at 6 weeks will be obtained. Peripheral blood will be collected for circulating immune phenotyping. Enrollment will occur at 3 participating institutions and is expected to be completed in 2022. Clinical trial information: NCT04551430.
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