Tumor habitat characteristics derived from intravoxel incoherent motion for early response assessment in soft tissue sarcoma undergoing neoadjuvant radiotherapy and targeted therapy: a phase II study

Background: Soft tissue sarcomas (STSs) are heterogeneous malignancies with limited reliable criteria for early response assessment. Commonly used criteria, such as Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, often underperform because treatment-related changes may not translate into tumor shrinkage. This study aimed to assess the potential of intravoxel incoherent motion (IVIM)-derived tumor habitat characteristics as biomarkers for assessing the treatment responses of STS patients who received neoadjuvant radiotherapy (neo-RT) along with targeted therapy. Methods: Patients with STS of the limbs or trunk from a prospective phase II trial were selected. All patients received magnetic resonance imaging (MRI) examinations pre- and post-neo-RT and targeted therapy. K-means clustering was employed to classify lesions into subregional habitats based on IVIM parameters. Postoperative pathology classified patients into good- and poor-response groups, defined as