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Abstract #2801

Defining the baseline functional imaging characteristics of retroperitoneal sarcomas

Jessica M Winfield1,2, Aisha Miah3, Dirk Strauss4, Khin Thway5, Andrew Hayes4, Daniel Henderson3, David J Collins1,2, Nandita M deSouza1,2, Martin O Leach1,2, Sharon L Giles1,2, Veronica A Morgan1,2, and Christina Messiou1,2

1MRI, Royal Marsden Hospital, Sutton, United Kingdom, 2Division of Radiotherapy and Imaging, Cancer Research UK Cancer Imaging Centre, Institute of Cancer Research, London, United Kingdom, 3Department of Radiotherapy, Royal Marsden Hospital, London, United Kingdom, 4Department of Surgery, Royal Marsden Hospital, London, United Kingdom, 5Department of Histopathology, Royal Marsden Hospital, London, United Kingdom

Soft tissue sarcomas are often highly heterogeneous tumours and post-treatment changes cannot be described by standard size criteria. Functional imaging may provide a non-invasive method of assessing response to treatment. Knowledge of baseline functional imaging characteristics and the repeatability of estimated parameters is essential in development of future studies. In this study, 22 patients with retroperitoneal sarcoma were imaged before treatment. Whole-tumour assessments of apparent diffusion coefficient (ADC), parameters of the intra-voxel incoherent motion model (IVIM: diffusion coefficient D, fraction f, fast exponential component D*), transverse relaxation rate (R2*), fat fraction and enhancing fraction (EF) showed large ranges of median estimates, indicating wide inter-tumour heterogeneity. The large standard deviation of parameters within tumours reflects the intra-tumour heterogeneity. In 21 patients, a second examination was carried out to assess repeatability of ADC, D, f, D* and R2*. Excellent repeatability of fitted parameters, particularly ADC, indicates high sensitivity to treatment-induced changes.

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