Prediction of Radiation Therapy Effects in Esophageal Cancer Using Diffusion and Perfusion MRI.

Chemoradiation therapy (CRT) of locally advanced esophageal cancer (LAEC), although improving outcomes of patients, still results in 50% of local failure. An early prediction could identify the patients at high-risk of poor response for individualized adaptive treatment. We aimed to investigate physiological changes in LAEC using diffusion and perfusion MRI for early prediction of treatment response. In the study, 115 LAEC patients treated with CRT were enrolled (67 in the discovery cohort and 48 in the validation cohort). MRI scans were performed pre-RT and at week 3 during RT (mid-RT). Gross tumour volume (GTV) of primary tumor was delineated on T2 weighted images. Within the GTV, the hypercellularity volume (VHC ) and high blood volume (VHBV ) were defined based upon the analysis of ADC and Vp histogram distributions within the tumors in the discovery cohort. The median GTV were 28cc±2.2cc at pre-RT and 16.7cc±1.5cc at mid-RT. Respectively, VHC and VHBV decreased from 4.7cc±0.7cc and 5.7cc±0.7cc at pre-RT to 2.8cc±0.4cc and 3.5cc±0.5cc at mid-RT. Smaller VHC at mid-RT (AUC=0.67, p=0.05; AUC=0.66, p=0.05) and more decreasing in VHC at mid-RT (AUC=0.7, p=0.01; AUC=0.69, p=0.03) were associated with longer PFS in both discovery and validation cohort. No significant predictive effects were shown in GTV and VHBV at any time point. In conclusions, we demonstrated that VHC represent aggressive subvolumes in LAEC. Further analysis will be carried out to confirm the correlations between the changes in image-phenotype subvolumes with local failure to determine the radiation-resistant tumor subvolumes, which may be useful for dose escalation.