PD-L1 expression in 522 selected sarcomas with subset analysis of recurrent or metastatic matched samples and association with tumour-infiltrating lymphocytes

We assessed the frequency of programmed death-ligand 1 (PD-L1) expression by immunohistochemistry (IHC) in a cohort of 522 sarcomas from 457 patients, incuding a subset of 46 patients with 63 matched samples from local recurrence or metastases with primary tumours and/or metachronous metastases. We also investigated the correlation of PD-L1 with the presence and degree of tumour-infiltrating lymphocytes (TILs) in a subset of cases. IHC was performed using the PD-L1 SP263 companion kit (VENTANA) on tissue microarrays from an archival cohort. Evaluation of PD-L1 and TILs was performed on full sections for a subset of 23 cases. Fisher’s exact and Mann Whitney test were used to establish significance (P <0.05). PD-L1 positive expression (≥1%) was identified in 31% of undifferentiated pleomorphic sarcomas, 29% of angiosarcomas, 26% of rhabdomyosarcomas, 18% of myxofibrosarcomas, 11% of leiomyosarcomas and 10% of dedifferentiated liposarcomas. Negative expression was present in all atypical lipomatous tumous/well-differentiated lipoasarcomas, myxoid liposarcomas, synovial sarcomas, pleomorphic liposarcomas, and Ewing sarcomas. PD-L1 IHC was concordant in 81% (38 of 47) of matched/paired samples. PD-L1 IHC was discordant in 19% (9 of 47 matched/paired samples), displaying differences in the proportion of cells expressing PD-L1 amongst paired samples with the percentage of PD-L1-positive cells increasing in the metastatic/recurrent site compared to the primary in 6 of 9 cases (67%). Significant correlation between PD-L1 expression and the degree of TILs was exclusively identified in the general cohort of leiomyosarcomas, but not in other sarcoma subtypes or in metastatic/recurrent samples. We conclude that the prevalence of PD-L1 expression in selected sarcomas is variable and likely to be clone dependent. Importantly, we demonstrated that PD-L1 can objectively increase in a small proportion of metastases/recurrent sarcomas, offering the potential of treatment benefit to immune checkpoint inhibitors in this metastatic setting.

Clinical features and prognosis of patients with liposarcoma: Single-center experience.

e22557 Background: Liposarcomas constitute 15% of all soft tissue sarcomas.They consist of four subtypes;well-differentiated,dedifferentiated,myxoid and pleomorphic.In this trial we assessed demographic and clinical features of patients with liposarcoma who were treated in our hospital.Methods: Patients who were diagnosed with liposarcoma in Hacettepe University Medical Oncology Department between 2005and2015(n = 119) were included. Patients’ data were collected from hospital registration system.Survival analyses were performed with Kaplan Meier analyses.Results: At the time of diagnosis, the vast majority of patients had localized and/or node positive disease(n = 98),8 patients had metastatic disease.Further analyses hold for only early stage disease:Median age was 52(min:18-max:81).105 patients(94.6%) had upfront surgery.26(23.4%) and 30 patients(27%) received perioperative chemotherapy(CT) and radiotherapy(RT),respectively.The most commonly used CT agents were ifosfamide, anthracyclines, etoposide,taxanes and gemcitabine.At a median follow-up of 45months, relapses were observed in 34 patients(30.6%) and 35 patients(31.5%) died.Median overall survival(OS) was 113.1 months and median relapse free survival (RFS) was 23.8 months.Perioperative CT and RT were not associated with improved RFS and OS.Among patients with early stage disease; median RFS of patients with well-differentiated, dedifferentiated, myxoid and pleomorphic subtypes were 31.8,34.3,28 and 5.2months,respectively(p = 0.013).Well-differentiated group had significantly higher RFS than those with pleomorphic liposarcomas(p = 0.003).The mostly used CT drugs in recurrent setting were ifosfamide+doxorubicine(42.9%) and ifosfamide+etoposide(21.4%).Conclusions: Liposarcoma prognosis varies significantly with histological subtype and the efficacy of systemic chemotherapy is limited both in early stage and advanced disease.[Table: see text]

Managing Liposarcomas: Cutting Through the Fat

Liposarcomas are one of the most common of more than 50 histologic subtypes of soft tissue sarcomas that, themselves, are heterogeneous. Liposarcomas fall into four distinct histologic subtypes: atypical lipomatous tumor/well-differentiated liposarcoma, dedifferentiated liposarcoma, myxoid (round cell) liposarcoma, and pleomorphic liposarcoma. Definitive treatment remains surgical resection with negative margins for resectable disease. However, well-differentiated liposarcomas that are large or difficult to operate upon should be followed with close surveillance as long as there is no radiologic concern for a dedifferentiated component. In contrast, first-line chemotherapy with anthracycline with or without ifosfamide, or gemcitabine and docetaxel should be used for inoperable myxoid (round cell) or pleomorphic liposarcomas, which are relatively responsive to chemotherapy. In the second- and third-line setting, myxoid liposarcomas, in particular, seem to be sensitive to trabectedin, which was recently approved by the US Food and Drug Administration (FDA). Eribulin offered a survival benefit when compared with dacarbazine in the third-line setting in liposarcomas (other than the well-differentiated subtype) and is now FDA approved. Recent studies have identified distinct genetic aberrations that not only aid in the diagnosis of liposarcoma subtypes but represent actionable targets. Cyclin-dependent kinase 4 and murine double minute 2 are overexpressed in well-differentiated and dedifferentiated liposarcomas and offer opportunities that are being pursued in clinical trials. It is critical that liposarcomas are not approached by oncologists as one disease entity but rather subclassified into distinct subtypes using histologic and molecular tools before formalizing a treatment plan.

DDIT3 Expression in Liposarcoma Development

Liposarcomas are mesenchymal tumors containing variable numbers of lipoblasts or adipocytes. The most common entities, well differentiated/dedifferentiated liposarcoma (WDLS/DDLS) and myxoid/round cell liposarcoma (MLS/RCLS), are both characterized by genetic rearrangements that affect the expression of the transcription factor DDIT3. DDIT3 induces liposarcoma morphology when ectopically expressed in a human fibrosarcoma. The role of DDIT3 in lipomatous tumors is, however, unclear. We have analyzed the expression of DDIT3 in 37 cases of liposarcoma (WDLS/DDLSn= 10, MLS/RCLSn= 16, and pleomorphic liposarcomas (PLS)n= 11) and 11 cases of common benign lipomas. Major cell subpopulations of WDLS/DDLS and MLS/RCLS tumors were found to express DDIT3 or the derived fusion protein, whereas PLS cases showed only a few positive cells. The lipomas contained large subpopulations expressing DDIT3. No correlation between numbers of DDIT3 expressing cells and numbers of lipoblasts/adipocytes was found. In vitro adipogenic treatment of two DDIT3 expressing cell lines induced lipid accumulation in small subpopulations only. Our results suggest a dual, promoting and limiting, role for DDIT3 in the formation of lipoblasts and liposarcoma morphology.