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Investigating Dynamic Contrast-Enhanced Magnetic Resonance Imaging as An Early Indicator of Response in Lung Stereotactic Body Radiation

C Williams

C Williams1*, J Lewis2 , J Tokuda1 , H Hatabu1 , M Nishino1 , R Mak1 , (1) Brigham and Women's Hospital, Boston, MA, (2) UCLA School of Medicine, Los Angeles, CA


WE-RAM3-GePD-JT-2 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Theater

Purpose: The goal of this study is to determine whether changes in pharmacokinetic properties of non-small cell lung cancers (NSCLCs) determined using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can be used as an early predictor of response to stereotactic body radiation therapy (SBRT).

Methods: This pilot study enrolled patients with inoperable stage I NSCLC and lesions between 1.5 cm and 6 cm in size that would be treated with SBRT. The prescribed dose was 54 Gy in 3 fractions or 50-60 Gy in 5 fractions. DCE-MRI was performed at four time points during therapy: baseline prior to SBRT, 1-2 days after the first fraction, 1-2 weeks after the end of the SBRT course, and 3 months after completing radiotherapy. For DCE-MRI, time-series images were acquired after bolus injection of contrast agent for three minutes using a 3D Turbo FLASH sequence, and the lesion was delineated in each frame using deformable contour propagation with manual editing. The mean intensity was calculated, and pharmacokinetic parameters were fit using a two-compartment model (plasma and extracellular, extravascular space) with a biexponential input function.

Results: Six patients have been enrolled on the study to date, and scans and pharmacokinetic parameters have been obtained on all available images for the first five patients (analysis of the sixth patient data set is in progress). The mean baseline kep (rate of transfer of contrast agent between the plasma and extracellular, extravascular space) of the lesions was 3.6 (range 1.9-6.8). Disparate trends in kep were observed during and after SBRT, with two lesions showing an increase, two showing a decrease and one remaining constant.

Conclusion: This study has demonstrated the feasibility of obtaining DCE-MRI scans and extracting pharmacokinetic parameters for stage I NSCLC patients treated with SBRT. Patient accrual and analysis of correlations with clinical outcomes is ongoing.

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