Application of Contrast-enhanced Ultrasound in Monitoring Soft Tissue Sarcoma Response to Neoadjuvant Radiotherapy

Overview

This pilot study will evaluate the feasibility of applying CEUS as imaging guidance for planning RT and predicting RT response. The investigators will determine if US-CT/MRI fusion is feasible and if tumor vascularity and pressure from CEUS can be used to reflect/predict the RT response. The investigators will perform CEUS three times: before the first neoadjuvant RT fraction, halfway through RT, and between the completion of RT and surgery. The fusion will be performed using previously acquired CT/MRI or on-site cone-beam CT with Bmode US. Once the fusion is successful, CEUS will be performed and panoramic 2D images (mimicking 3D) will be collected for the whole tumor. If the fusion is not feasible or successful, the investigators will perform CEUS side by side with CT/MRI and collect images. The investigators will quantify tumoral vascularity comparing Bmode area/volume (total tumor) and contrast-enhanced area/volume (vascular region) at each time point. Subharmonic amplitudes in the tumor area/volume will be quantified to estimate tumoral pressure (known to be the same level as interstitial fluid pressure (IFP)). Quantified vascularity and pressure at each time point will be compared with the tumor size change at later study points as well as the histological outcome after the surgery.

This is an open-label, non-randomized, human trial that will be conducted at one clinical site, Thomas Jefferson University. Our subjects will be patients with localized STS scheduled for neoadjuvant RT based upon the recommendations of our multidisciplinary sarcoma tumor board. All subjects will have an unenhanced (baseline) conventional US followed by CEUS study with infusion of ultrasound contrast agent (Definity; Lantheus Medical Imaging). The investigators will collect the study data at three time points: 1) prior to the first RT fraction, 2) middle of RT (e.g., any day on 3rd week of 5 week-long RT), and 3) between the completion of RT and surgery. The ultrasound contrast administration will be an intravenous infusion of 2 vials of Definity/50ml saline will be administered as an IV infusion via a peripheral vein (preferably the antecubital vein), with infusion rates of 4 to 10 ml/min (titrated to effect) through an 18-22 gauge angiocatheter. During the contrast infusion, CEUS data will be collected. On the study visit, the investigators first perform conventional US including Doppler imaging using a C2-9VN probe (with embedded electromagnetic sensors) on Loqiq E10 (GE HealthCare) to locate the whole tumor and select the planes for fusion. The US scanner has dedicated fusion software, and the investigators will load the pre-obtained CT/MRI (most recent CT/MRI by standard of care) on US scanner and fuse it with real-time US by selecting references points under the magnetic field created by an electromagnetic transmitter near a subject. Once the fusion is done (if the fusion fails or unsatisfactory, the investigators will perform CEUS alone), the investigators will start the infusion UCA, Definity (3 ml of Definity suspended in 50 ml saline) via a peripheral vein (preferably the antecubital vein), with infusion rates of 4 to 10 ml/min (titrated to effect) through an 18-22 gauge angiocatheter. The dosage was selected based on our previous work in monitoring breast tumor IFP in humans. Conventional CEUS images will be collected as 2D movie clips sweeping over 3D tumor volume during infusion. Then, the investigators will turn on SHAPE mode. The investigators will determine the optimum SHAPE settings (where the subharmonic signal changed the most, which will vary among subjects) for each subject and infusion will be stopped during this process. With restarting the infusion, the SHAPE data will be collected with individually determined acoustic power, which allows us to compare the pressure between subjects independently of an operator and other imaging settings. Another set of SHAPE data will be acquired at the same acoustic output power setting with no UCA after roughly 5 minutes (to allow for clearance of bubbles).