Contrast enhanced ultrasound versus MRI for response assessment of extra-abdominal desmoid Fibromatosis- A feasibility study

Abstract

Background Desmoid Fibromatosis (DF) is a locally aggressive soft tissue tumor which was traditionally managed with surgical excision. However due to high rates of local recurrence and insights about its behavior, there is now a paradigm shift towards active surveillance and medical management. Imaging plays a crucial role in surveillance and treatment response; however, conventional RECIST criteria are not adequate for DF. MRI is the preferred modality but faces limitation in availability and uniformity. Although ultrasound (US) is not optimal for evaluation, contrast enhanced US has shown promising results in many solid tumors. Objectives To explore the role of Contrast Enhanced Ultrasound (CEUS) as a response assessment tool in DF. Materials and Methods This was a prospective study conducted between March 2022 and December 2023 and included 21 adults with DF who received medical line of treatment. A combination of clinical evaluation for symptom relief, and imaging modalities using MRI and CEUS, were utilized for response assessment. Statistical analysis was performed using non parametric tests. Results Out of 21, 19 patients underwent pre as well as post-treatment evaluation. Clinical improvement was reported by 73.68 % while MRI indicated response only in 41.18 %; whereas only 29.41 % met the criteria for partial response according to RECIST 1.1. All responders on MRI exhibited continued enhancement on CEUS with a significant decrease in Mean Transit Time (MTT, p = 0.047). Conclusion CEUS demonstrates potential as an effective treatment response tool in DF, providing real-time information of microvascular changes within the mass.