Application Of MRI Imaging Markers In Evaluating Tumor Response To Cyberknife Therapy For Small Hepatocellular Carcinoma

Objective:To study the Magnetic Resonance Imaging（MRI）of small Hepatocellular carcinoma（s HCC）after cyberknife stereotactic radiosurgery（CK）,The trend analysis of MRI related imaging markers,the role of ADC value in early tumor response evaluation and the influencing factors of MRI imaging markers predicting early objective remission after s HCC cyberknife treatment.Methods:（1）A total of 45 patients with pathologically or clinically confirmed SHCC in Ruikang Hospital Affiliated to Guangxi University of Traditional Chinese Medicine from February 2017 to December 2019 were collected as the research subjects.The follow-up cutoff time was 1 year,and the clinical data and imaging data of the admitted patients were complete.（2）All patients were treated with G3 type CK at a total dose of 42-45Gy.Segmentation of 3-4 exposures.All lesions were scanned with the same MRI scan protocol using Philips Ingenia1.5T MRI at 1 week before treatment（baseline）,2-3 months,5-6 months and 11-12 months after treatment,and all images were post-processed using a standardized procedure.Main measurement for diameter,focal lesions T2 signal intensity ratio,lesions enhanced arterial signal intensity ratio and absolute value of ADC.All cases of image data,review of the evaluation criteria according to the improvement of solid tumors（Modified Response Evaluation Criteriain Solid Tumor mRECIST）tumor lesion response assessment.（3）All follow-up data were divided into three groups:early group（2-3 months）,middle group（5-6 months）,and late group（11-12 months）.Each group was evaluated according to Mrecist criteria,and the evaluation grade was divided into complete response（CR）,partial response（PR）,stable disease（SD）,and disease progression（PD）.Patients assessed as complete response and partial response（CR+PR）were divided into objective response group,and patients assessed as stable disease（SD）were divided into stable group.The T2 signal intensity ratio,arterial phase signal intensity ratio,and absolute value of ADC in each group were contrastively and longitudinally analyzed.At the same time,univariate and multivariate analyses were performed to predict the early efficacy of cyberknife therapy for s HCC in combination with the baseline diameter of the lesions.Results:（1）Comparison of T2 signal intensity ratio between groups in the 1-year follow-up period of all cases showed that pair comparison before and after baseline,early（2-3months）,middle（5-6 months）,and late（11-12 months）showed no difference except that there was no difference between the middle（5-6 months）and the late（11-12 months）,while the others were different（P<0.001）.The early（2-3 months）review showed an upward trend,while the middle（5-6 months）review showed a downward trend.Comparison of signal intensity ratio in enhanced arterial phase between groups showed that pair comparison before and after baseline,early（2-3 months）,middle（5-6 months）and late（11-12 months）showed no difference except that there was no difference between middle（5-6 months）and late（11-12 months）,and the others were different（P<0.001）.Early（2-3 months）and middle（5-6months）reviews showed a downward trend.Comparison of absolute value ADC between groups showed that there were differences before and after the early（2-3 months）,the middle（5-6 months）,and the late（11-12 months）（P<0.001）,and the overall trend was increased during the follow-up.（2）The tumor response of s HCC stereotactic radiotherapy was evaluated according to mRECIST criteria.The areas under the ROC curve of objective remission group（CR+DR）in early stage（2-3 months）,middle stage（5-6 months）and late stage（11-12 months）were 0.576,0.523 and 0.639,respectively.The diagnostic cutoff values were ADC values of1.161,1.086 and 1.295,respectively.The sensitivity and specificity of diagnosis were 60.60%,80.20%,82.10%and 66.70%,42.10%,47.10%,respectively.During the early follow-up（2-3months）,the absolute value of ADC in objective remission group（CR+DR）was 1.15±0.11×10^-3s/mm²,and that in stable group was 1.22±0.21×10^-3s/mm².There was no significant difference between the two groups（P=0.151）.The absolute difference of ADC（ΔADC）in objective remission group（CR+DR）was-0.19±0.08×10^-3s/mm²,and that in stable group was-0.04±0.08×10^-3s/mm².There was significant difference between the two groups（P<0.001）.The absolute value of ADC in the early objective remission group（CR+DR）after radiosurgery was significantly higher than that in the stable group.（3）Tumor responses to s HCC cyberknife stereotaxic radiotherapy were assessed according to m MRECIST criteria,univariate analysis of baseline（pre-treatment）tumor diameter,T2 signal intensity ratio,enhanced arterial signal intensity ratio,and absolute ADC prediction of early（2-3 months）objective response（CR+DR）.Baseline（pre-treatment）tumor diameter and ADC value were important influencing factors（P<0.001）.Multivariate Logistic regression analysis showed that baseline（pre-treatment）tumor diameter was an independent influencing factor（P<0.001,OR=0.054）.（4）Comparison of absolute ADC values in the peri-tumor radio-induced liver injury area during the 1 year follow-up after the cyberknife stereotactic radiotherapy of SHCC showed that there were differences before and after the early（2-3 months）,the middle（5-6months）,and the late（11-12 months）（P<0.001）,and there was an overall increasing trend during the follow-up.Conclusion:During the 1 year follow-up of all patients with SHCC after cyberknife stereotactic radiotherapy,it was found that（1）the imaging marker T2 signal intensity showed an increasing trend compared with the early stage（2-3 months）,a decreasing trend in the middle stage,and a 6 trend was not obvious in the late stage.Compared with early（2-3months）and middle（5-6 months）,the intensity of enhanced signal in arterial stage showed a decreasing trend,but the decreasing trend was not obvious in late stage.（2）The absolute value of ADC of imaging markers showed an overall increasing trend.The absolute value of ADC of tumor may change earlier than that of tumor morphology.TheΔADC value in the early assessment objective response（CR+DR）group was higher than that in the stable（SD）group.ΔADC value has the potential to be used as a quantitative indicator to assess early tumor response.（3）Tumor response was assessed using m MRECIST criteria.Tumor diameter at baseline（before treatment）was an independent predictor of early objective response in s HCC.The smaller the tumor diameter of s HCC,the more likely it was to achieve early objective response after cyberknife stereotaxic radiotherapy.（4）The absolute value of ADC,a radiological marker in the peri-tumor liver injury area,showed an overall increasing trend,reflecting the histopathological changes of liver tissue after irradiation over time.