Abstract 1655P
Background
Epithelioid hemangioendothelioma (EHE) is a rare sarcoma with vascular differentiation. Tumors may exhibit a spectrum of behaviour ranging from an indolent to aggressive clinical course with widespread metastases. There remains no consensus on how to manage this disease, and there is a pressing need for improved systemic therapies, particularly in the metastatic setting. We hypothesize that a subset of EHE carry molecular aberrations that may act as strong antigenic targets for eliciting immune response.
Methods
Cases of EHE were identified from the Toronto Sarcoma Program database. All available slides were re-reviewed to confirm the diagnosis and, where sufficient material was available, independent molecular confirmation was performed (RNA-Seq). Each of the tumors were stained for tumor-infiltrating lymphocytes (TILS), using the following markers: CD3, CD4, CD8, CD20 and CD68; TILs were quantified by standard techniques. Pending at the time of abstract submission, DNA was also extracted from (i) the tissue blocks for whole exome sequencing (WES), and (ii) from blood samples for quantification of circulating tumor DNA estimation.
Results
Sixteen patients fulfilled the inclusion criteria, with material available in eight cases. The samples were all obtained from metastatic sites, including: liver (n= 4), lung (n= 2), and soft tissue (n= 2). CD3+, CD4+, CD8+, CD68+ T cell infiltration (threshold set >11 cells/HPF) was seen in 75%, 50%, 38% and 0% respectively in the analyzed tissue samples. All eight analyzed tissues samples showed no infiltration of CD20+.
Conclusions
Our results suggest EHE represents an immunologically “cold” tumor. While preliminary, this data raises the possibility that single agent checkpoint inhibition may be of limited value in EHE and novel strategies are required to turn this disease into “hot” tumors when considering immune-therapeutics. Updated data for all 16 patients will be presented at the meeting if accepted.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Toronto Sarcoma Program.
Funding
Toronto Sarcoma Group.
Disclosure
A. Abdul Razak: Advisory/Consultancy, Research grant/Funding (institution): Lilly; Advisory/Consultancy, Research grant/Funding (institution): Merck; Advisory/Consultancy, Research grant/Funding (institution): Boehringer Ingelheim. All other authors have declared no conflicts of interest.