Repeatability and correlations of dynamic contrast enhanced and T2* MRI in patients with advanced pancreatic ductal adenocarcinoma

Abstract

BackgroundIn current oncological practice of pancreatic ductal adenocarcinoma (PDAC), there is a great demand for response predictors and markers for early treatment evaluation. In this study, we investigated the repeatability and the interaction of dynamic contrast enhanced (DCE) and T2* MRI in patients with advanced PDAC to enable for such evaluation using these techniques. Materials & methods15 PDAC patients underwent two DCE, T2* and anatomical 3 T MRI sessions before start of treatment. Parametric maps were calculated for the transfer constant (Ktrans), rate constant (kep), extracellular extravascular space (ve) and perfusion fraction (vp). Quantitative R2* (1/T2*) maps were obtained from the multi-echo T2* images. Differences between normal and cancerous pancreas were determined using a Wilcoxon matched pairs test. Repeatability was obtained using Bland-Altman analysis and relations between DCE and T2*/R2* were observed by Spearman correlation and voxel-wise binned plots of tumor voxels. ResultsPDAC Ktrans (p = 0.007), kep (p < 0.001), vp (p = 0.035) were lower and ve (p < 0.001) was higher compared to normal pancreas. The coefficient of variation between sessions was 21.8% for Ktrans, 9.9% for kep, 19.3% for ve, 18.2% for vp and 18.7% for R2*. Variation between patients ranged from 20.2% for kep to 43.6% for Ktrans. In the tumor both Ktrans (r = 0.56, p = 0.030) and ve (r = 0.54, p = 0.037) showed a positive correlation with T2*. Voxel wise analysis showed a steep increase in R2* for tumor voxels with lower Ktrans and ve. ConclusionWe showed good repeatability of DCE and T2* related MRI parameters in advanced PDAC patients. Furthermore, we have illustrated the relation of DCE Ktrans and ve with tissue T2* and R2* indicating substantial value of these parameters for detecting tumor hypoxia in future studies. The results from our study pave the way for further response evaluation studies and patient selection based on DCE and T2* parameters.