# Clinical insights into circulating free-DNA in patients with bone sarcomas and ewing sarcoma

## TL;DR

This study explores the use of liquid biopsy to detect genetic mutations in bone sarcoma patients, highlighting a novel mutation in osteosarcoma.

## Contribution

The study identifies a novel IDH2 mutation in osteosarcoma and demonstrates the feasibility of ctDNA detection in sarcoma patients.

## Key findings

- Mutations in IDH2 and TP53 genes were detected in plasma samples from sarcoma patients.
- A novel IDH2 (R172K) mutation was identified in a patient with osteosarcoma.
- ctDNA detection is feasible in sarcoma patients and could improve diagnosis and monitoring.

## Abstract

•Non-invasive ctDNA monitoring shows promise for sarcoma patient management.•ddPCR identified IDH2 and TP53 mutations in bone sarcoma plasma samples.•Liquid biopsy could improve bone sarcoma diagnosis.•Study highlights the detection of a novel IDH2 mutation in osteosarcoma.

Non-invasive ctDNA monitoring shows promise for sarcoma patient management.

ddPCR identified IDH2 and TP53 mutations in bone sarcoma plasma samples.

Liquid biopsy could improve bone sarcoma diagnosis.

Study highlights the detection of a novel IDH2 mutation in osteosarcoma.

Sarcomas represent a heterogeneous group of malignancies characterized by varying clinical behaviors and treatment responses. Liquid biopsy has emerged as a promising non-invasive method for monitoring tumor dynamics by detecting actionable mutations in cancer patients. The emergence of circulating DNA as a non-invasive biomarker offers promising avenues for improving diagnostic accuracy and treatment monitoring in sarcoma patients.

In this study, the authors employed mutation-specific droplet digital PCR (ddPCR) to analyze tumor-derived cell-free DNA, also known as circulating tumor DNA (ctDNA), belonging to plasma samples of sarcoma patients, aiming to characterize mutation profiles in the IDH2 and TP53 genes. Between July 2019 and June 2023, the authors collected and analyzed 38 samples from patients diagnosed with osteosarcoma, chondrosarcoma, or Ewing's sarcoma. Histopathological confirmation of diagnoses was performed, followed by ddPCR analysis on 36 valid plasma samples.

The results showed mutations in three out of thirty-six sarcoma patients. Patient 1 exhibited a 12.6 % mutant IDH2 (R172S) allele fraction, Patient 2 had a 0.27 % mutant TP53 (R175H), and Patient 3 showed a 17 % mutant IDH2 (R172K). Notably, Patients 1 and 2 were diagnosed with chondrosarcoma, while Patient 3 had osteosarcoma.

The present study provided evidence for the feasibility of ctDNA detection in sarcoma patients, where mutations were found in IDH2 and TP53 genes, including a novel IDH2 mutation in osteosarcoma. The evaluation of ctDNA has the potential to transform clinical strategies in this challenging group of malignancies and this may be further confirmed in larger cohort studies. Continued research efforts are essential to optimize ctDNA detection methods and validate its utility across diverse sarcoma subtypes.