PET/CT in brachytherapy early response evaluation of pancreatic ductal adenocarcinoma xenografts: comparison with apparent diffusion coefficient from diffusion-weighted MR imaging

ObjectiveTo evaluate the feasibility of using PET/CT and diffusion-weighted magnetic resonance imaging (DW-MRI) to monitor the early response of pancreatic ductal adenocarcinoma (PDAC) xenografts to brachytherapy, and to determine whether maximum standardized uptake value (SUVmax) correlate with apparent diffusion coefficient (ADC).Materials and MethodsSW1990 human PDAC were subcutaneously implanted in 20 nude mice. They were randomly divided into 125-Iodine (I-125) seeds and blank seeds group. PET/CT and DW-MRI were performed at pretreatment and 5days after therapy. SUVmax and ADC values were calculated, respectively. The correlation between SUVmax and ADC values was analyzed by the Pearson correlation test.ResultsThe SUVmax were significantly decreased between pretreatment and 5days after I-125 seeds treatment (p<0.001) and between two groups (p<0.001). And the ADC values were significantly increased between pretreatment and 5days after I-125 seeds treatment (p<0.001) and between two groups (p<0.001). While in the bank seeds group, there were no significantly difference between pretreatment and after treatment in SUVmax and ADC values (p=0.057; p=0.397). SUVmax and ADC correlated significantly and negatively before treatment in both groups (r=-0.964, R-2=0.929, p<0.001; r=-0.917, R-2=0.841, p<0.001) and after treatment in the blank seeds group (r=-0.944, R-2=0.891, p<0.001). But after I-125 seeds treatment there was no significant correlation between SUVmax and ADC (r=-0.388, R-2=0.151, p=0.268).ConclusionThe PET/CT and DW-MRI are capable of monitoring the early response of PDAC xenografts to brachytherapy. The significantly inverse correlation between pretreatment SUVmax and ADC suggests that PET/CT and DW-MRI might play complementary roles for therapy assessment.