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2187. Evaluation of 3D Dynamic Contrast-Enhanced Ultrasound for Early Assessment of Treatment Response in Metastatic Liver Lesions
Authors * Denotes Presenting Author
  1. Amir Pirmoazen *; San Joaquin General Hospital; Stanford University
  2. Neha Antil; Stanford University
  3. Dimitre Hristov; Stanford University
  4. Ahmed El Kaffas; Stanford University
  5. Aya Kamaya; Stanford University
Objective:
To evaluate quantitative 3D dynamic contrast-enhanced ultrasound (DCE-US) perfusion parameters as non-invasive imaging biomarkers for early assessment of treatment response in metastatic liver lesions, against response evaluation criteria in solid tumors version 1.1 (RECIST 1.1).

Materials and Methods:
12 patients (7 men, 5 women) with metastatic liver lesions were prospectively recruited in this ongoing HIPAA-compliant IRB-approved study. Informed consent was obtained from all participants. Each patient was scanned before and 14 days after initiation of treatment using a Philips EPIQ 7 US machine coupled to an X6-1 3D probe. Definity® microbubbles (contrast agent used off label) were intravenously injected as a bolus (0.2 mL followed by saline flush over 3 minutes). All contrast data was acquired in volumetric contrast-specific imaging at a frame rate of 1.5-4 Hz using power modulation with a low mechanical index (MI = 0.09) to prevent microbubble destruction. Volumes of interest (VOI) were used to segment the lesion in each image, and a time-intensity curve (TIC) was extracted for each VOI. Time-to-peak (TP) and mean-transit-time (MTT) parameters to evaluate changes in tumor blood flow, along with peak enhancement (PE) and area under the curve (AUC) parameters to assess changes in the blood volume were obtained using a lognormal fit to the bolus TIC. Tumor response to treatment was characterized as a responder or non-responder based on RECIST 1.1.

Results:
A total of 24 study sessions conducted in 12 patients (five with metastatic liver lesions from colorectal adenocarcinoma and seven from pancreatic origin) were analyzed. We observed that decreases in blood volume parameters were predictive of RECIST 1.1. More specifically, 6 out of 8 responder patients had a reduction of up to 84% in the quantified PE parameters, and 4 out of 8 responder patients had a reduction of up to 82% in the quantified AUC parameters. In contrast, 3 out of 4 non-responder patients had an increase of up to 23 folds in both PE and AUC. Minimal predictions of response were noted from blood flow parameters. Furthermore, comparisons of bolus perfusion parameters obtained in 3D DCE-US outperformed those obtained in 2D DCE-US in the same patients.

Conclusion:
Quantified 3D DCE-US blood volume parameters are promising imaging biomarkers for early treatment response assessment in patients with liver metastasis.