Predicting Radiotherapy Response and Toxicities in Soft Tissue Sarcoma of the Extremities - Cohort B

This is a multicentre prospective cohort study, primarily aimed at reporting the frequency and intensity of radiotherapy side-effects of patients with soft tissues sarcoma of the extremities (STSE). Two sub-studies are proposed within this study: * MRI radiation response assessment Aimed at establishing whether changes in median apparent diffusion coefficients (ADC) are predictive of pre-operative STSE response measured using histopathology. * Biomarker development and Immune mediators associated with radiotherapy Aimed at establishing prognostic markers which may refine selection of cases for pre-operative, palliative or no radiotherapy. Also, aimed at determining if radiotherapy stimulates the tumour microenvironment, resulting in measurable change in anti-tumour immunity and if certain subtypes could potentially benefit from the addition of immunotherapy with radiation. Patients participation in the sub-studies is optional.