# The Use of Positron-Emission Tomography–Magnetic Resonance Imaging to Improve the Local Staging of Disease in Myxofibrosarcoma: A Feasibility Study

## TL;DR

This study explores whether combining PET-MRI and DWI MRI improves the accuracy of staging myxofibrosarcomas compared to standard MRI.

## Contribution

The study introduces a novel feasibility approach using FDG-PET and DWI MRI for better pre-operative staging of myxofibrosarcomas.

## Key findings

- Combining FDG-PET and DWI MRI may provide more accurate local staging of MFSs than conventional MRI.
- Five out of six patients had close or positive surgical margins, highlighting the need for improved imaging.
- The study demonstrates the practicality of using PET-MRI and DWI for pre-operative planning in MFSs.

## Abstract

Background/Objectives: Myxofibrosarcomas (MFSs) are aggressive soft-tissue sarcomas (STSs) that often arise in the upper and lower limbs. MFSs are a highly infiltrative sarcoma subtype with a high positive margin rate and poor clinical outcomes. Their management involves multidisciplinary team (MDT) input, with the mainstay of treatment being a wide surgical resection to remove the whole tumour, but this can be challenging due to the infiltrative nature of MFSs through fascial planes. Appropriate pre-operative imaging is therefore essential for surgical planning. Currently, MRI imaging is the modality of choice to assess the soft-tissue extent of MFSs; however, it does not always reliably predict tumour extent, especially when an MRI shows high-signal curvilinear projections, known as “tails”, which often represent tumour extension and increase the risk of positive margins and local recurrence. Methods: This feasibility study therefore aimed to investigate whether the addition of an FDG PET-MRI and DWI MRI is superior for the local staging of MFSs compared to a standard MRI, and to assess its practicality for clinical use. Results: Of the eight patients recruited, six completed the required scans, proceeded to surgery, and were included in the data analyses. Five of the six patients had close (<2 mm) or positive margins requiring re-excision. Conclusions: Our results show that combining an FDG-PET and DWI MRI may offer a more accurate local staging of MFSs than a conventional MRI; however, a larger prospective trial is needed to further investigate this pilot data. Nevertheless, this novel feasibly study demonstrates the potential use of PET-MRI and DWI for improving pre-operative planning prior to the surgical resection of MFSs.