1945P - Diagnostic and therapeutic impact of liquid biopsy in soft tissue sarcomas: A case series

Background

Soft tissue sarcomas (STS) are a group of rare heterogeneous mesenchymal tumours with distinct clinical and molecular features. Current therapeutic approaches in advanced STS are limited to conventional chemotherapy and targeted therapy without significant impact on survival. Liquid biopsy (LB) or cell-free DNA is an innovative tool in cancer practice that detects particular molecular alterations (MA) with diagnostic and therapeutic implications. In this case series, we report the outcomes of LB in a cohort of international STS patients.

Methods

In this prospective cohort, all STS patients from the international department treated in Gustave Roussy Cancer Campus that underwent a LB during their disease course between 01/2022 and 03/2023 were included. Demographic data were gathered with various significant MA.

Results

18 STS patients were included in this series with a median age of 49 yrs. 9 were men (50%) and all patients had inoperable or metastatic disease at the time of LB. They had a median of 1 prior line of therapy. Three patients had a high TMB (tumour mutational burden) (16.6%) with more than 10 mut/mb. Four patients (22.2%) had targetable MA: Three pts had MSI-high tumors (microsatellite instability, two uterine leiomyosarcoma and 1 with GIST) with high sensitivity to immune checkpoint inhibitors and 1 angiosarcoma patient had BRAF mutation in which a BRAF and MEK inhibitors were introduced. On the other hand, four patients had confirmed STS diagnosis with the detection of fusion transcripts: two had Ewing sarcoma, one had desmoplastic round cell tumour and one patient had the EWSR1-ATF1 fusion transcript which helped changing the diagnosis from suspected melanoma to clear cell sarcoma. Also four patients had genetic counselling after detecting germline mutations (2 NF1 in GIST and MPNST, 1 APC in desmoid tumor and 1 POLD1 in chondrosarcoma). Two patients benefited from haematology referral after confirmed JAK2 mutations.

Conclusions

LB proved to be an attractive technique to detect significant MA in advanced STS, a group of malignant tumors with a challenging diagnosis and therapeutic approach. This tool can be implemented as an adjunct tool to offer novel therapeutic options to patients as well as fine-tuning of the diagnostic process.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.