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Targetability of Adult Soft Tissue Sarcomas for Mild Hyperthermia Treatments Using Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound

J Cammin

J Cammin1*, S Kothapalli2 , H Chen2 , A Partanen3 , I Zoberi1 , M Altman1 , (1) Washington University in St. Louis, Department of Radiation Oncology, St. Louis, MO , (2) Washington University in St. Louis, Department of Biomedical Engineering, St. Louis, MO , (3) Philips, Clinical Science MR Therapy, Andover, MA


TU-FG-708-5 (Tuesday, August 1, 2017) 1:45 PM - 3:45 PM Room: 708

Purpose: To assess the applicability of MR-HIFU for mild-hyperthermia (MHT) in conjunction with radiation or chemo therapy (RT/CT) in adult soft-tissue sarcomas (STS) and to estimate the number of required MHT sessions.

Methods: A database of computed tomography images of adult extremity STS patients treated with external-beam radiation were retrospectively assessed for tumor accessibility with a commercial MR-HIFU therapy planning software (Sonalleve, Philips). The MHT target was the GTV defined for radiation treatment planning. Targetability was scored based on tumor location, volume, and depth, structures within and/or beyond the HIFU beam path, and the physical parameters of the Sonalleve MR-HIFU system. Published MR thermometry data (Tillander et al., 2016) was used to estimate the achievable heating volume for a target temperature of 41°C.

Results: 8/10 consecutive patients were determined to have HIFU-accessible STS. Imaging data sets from these 8 patients (ages 33 to 88) were analyzed. Tumor locations included lower leg, thigh, humerus, upper arm, and buttock. The mean tumor volume was 677±278 cc (range: 152–1169 cc). The number of required HIFU sonications was given by the ratio of tumor volume (minus volumes near critical structures) to the volume (100 cc) of a 44-mm diameter heating cell. The accessibility of each proposed treatment cell location was verified. The mean number of required MHT sonications was 7.25±2.7 (range: 2–8).

Conclusion: Extremity STS in adults may be treated with MHT adjuvant to RT/CT using a commercially available MR-HIFU system. Large target volumes and size limitations of the HIFU treatment cells require splitting the treatment into multiple fractions. This can be accommodated with one or two MHT sessions per week over the course of RT. We are currently expanding the patient database for this study, and acquire new data to assess the heating properties of the treatment cells.

Funding Support, Disclosures, and Conflict of Interest: A. Partanen is an employee of Philips Healthcare.

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