The Evaluation of Cytokines and Hormones as Biomarkers for Epithelioid Haemangioendothelioma and Generation of Patient-derived Preclinical Models to Assess the Activity of Anticancer Agents and Validate Novel Therapeutic Targets

Epithelioid hemangioendothelioma (EHE) is an ultra-rare (incidence rate < 1/1000.000), translocated, vascular soft tissue sarcoma. It shows a pick of incidence in the 4th decade of life, and it is more commonly diagnosed in females, with reported disease onset during pregnancy.

Two specific translocations have been identified in EHE, representing an hallmark in diagnosis today: the fusion of Transcriptional Co-activator with a PDZ-motif (TAZ) with Calmodulin Binding Transcription Activator 1 (CAMTA1) which is present in almost 90 % of cases, and the fusion of Yes-associated Protein (YAP) and Transcription Factor E3 (TFE3) genes (YAP-TFE3), which can be found in around 10% of the patients. YAP and TAZ are well-defined downstream effectors in the Hippo pathway. Forced activation of YAP/TAZ is thought to drive EHE and contribute to key aspects of the cancer phenotype, including metastasis and fibrosis.

Most of the times, EHE presents as multifocal or metastatic at diagnosis, with lung, liver and bone being the more commonly involved. The clinical course ranges from cases naturally stable over time to those highly aggressive and rapidly fatal. Pleural effusion, lymph node metastases and pathologic features (nuclear pleomorphism, mitotic figures and presence of necrosis) have been reported to be associated with a worse outcome, but biological and molecular predictors are still lacking. In particular, there is a subgroup of EHE presenting with serosal involvement, typically associated with chronic mild fever, weight loss, asthenia, anorexia, severe disease- related pain, (more responsive to anti-inflammatory pain killers that morphine), and dyspnoea which seems to perform very poorly. The biological basis sustaining this presentation is completely unknown.

As of today, there are no reports available in literature providing a comprehensive description of the peculiar EHE radiological features, both for primary and metastatic disease at different sites, and their potential prognostic role has not been explored. In addition, there are no published data to indicate the optimal routine follow-up policy of surgically treated EHE patients with localised disease and the routine follow-up schedules differ across institutions. The appropriate frequency of imaging in cases suffering of distant metastases is also left to be determined.

Also, the definition of radiological progression and the assessment of treatment response in EHE remain major challenges. The appearance or worsening of serosal effusion, the changes in serosal involvement and the limited increase in size over a short-time interval in slow-growing variants are not promptly captured by Response Evaluation Criteria for Solid Tumor (RECIST) definition for disease progression. This makes the use of such criteria unsatisfactory in this complex disease and could potentially lead to a delay in progression recognition and treatment start. Similarly, being frequently observed in EHE under treatment, improvement of serosal effusion, reduction in size <30%, and correlation between radiology and symptoms should be taken into account when assessing treatment response.