Comparison of spatial location and dynamic changes of functional parameters of primary tumors of thoracic esophageal cancer based on DWI and 18F-FDG PET-CT before and during radiotherapy / 中华放射肿瘤学杂志

ABSTRACT

Objective:To evaluate the spatial position and functional parameters of 18F-FDG PET-CT and diffusion-weighted imaging (DWI) before and during radiotherapy (RT) based on the medium of 3DCT in patients with esophageal cancer and to explore whether the high-signal area derived from DWI can be used for individualized definition of the volume in need of dose-escalation for esophageal cancer. Methods:Thirty-two patients with esophageal cancer treated with concurrent chemoradiotherapy or neoadjuvant chemoradiation sequentially underwent repeated 3DCT, 18F-FDG PET-CT and enhanced MRI scans before RT and at the 15 th time of RT. All images were fused with the 3DCT images by deformable registration. The gross tumor volume (GTV) was delineated based on PET Edge on the first and second 3DCT, PET-CT and DWI and corresponding T 2-weighted MRI (T 2W-MRI) fused images, and defined as GTV CTpre and GTV CTdur, GTV PETpre, GTV PETdur, GTV DWIpre and GTV DWIdur, respectively. SUV (SUV max, SUV mean, SUV peak), MTV, TLG, ADC (ADC min and ADC mean) values and △SUV (△SUV max, △SUV mean, △SUV peak), △MTV, △TLG, △ADC (△ADC mean and △ADC min) of lesions were measured before and during RT. Results:The differences in SUV (SUV max, SUV mean, SUV peak), MTV, TLG, ADC mean and ADC min of the GTV before and during RT were statistically significant (all P<0.001). The tumor ADC and SUV values before and during RT showed no significant correlation, and there was no correlation between △ADC and △SUV (both P>0.05). The conformity index (CI) of GTV PETpre to GTV DWIpre was significantly higher than that of GTV PETdur to GTV DWIdur ( P<0.001). The shrinkage rate of maximum diameter (△LD DWI)(24%) and the shrinkage rate of tumor volume (VRR DWI)(60%) based on DWI during RT were significantly greater than the corresponding PET-based △LD PET (14%) and VRR PET (41%)( P=0.017 and P<0.001). Conclusions:The location of high residual FDG uptake based on PET-CT yields poor spatial matching compared with the area with residual high signal based on DWI during RT. Tumor ADC and SUV values may play complementary roles as imaging markers for prediction of patterns of failure and for definition of the volume in need of dose-escalation. In addition, the shrinkage rates of tumor maximum diameter/volume based on DWI during RT are significantly faster than those based on PET-CT. Therefore, the feasibility of selecting boosting of the high signal area derived from DWI for individualized definition of the volume for esophageal cancer is not clear.