The Early Assessment Based On Contrast-enhanced CT Combined With DWI-MRI For Conversion Therapy In Unresectable Gastric Cancer

Purpose:To investigate the early assessment based on contrast-enhanced computed tomography(CE-CT)combined with the apparent diffusion coefficient(ADC)of diffusion weighted imaging(DWI)for conversion therapy inunresectable gastric cancer.Method:The patients with unresectable gastric cancer underwent CE-CTs within 7 days before first conversion therapy and after 3 periods of conversion therapy,respectively.Magnetic resonance imaging(MRI)were performed within 7 days before and 24-48 hours after first conversion therapy and after 3 periods of conversion therapy,respectively.According to Response Evaluation Criteria in Solid Tumors(Recist,version 1.1),the patients were divided into effective and ineffective groups.CT value were measured at the most prominent enhancement site of the tumor both on the plain scan and venous phase,and then were used for calculating the change rate of intensity before and after chemotherapy.The two groups were compared to determine whether there was statistical significance.ADC value were measured at the same regions as those in CT(ADClocal)and the whole region of the tumor(ADCemire),respectively.Then the change and diagnostic efficacy of ADC value were compared between the two groups.Finally,we combined CE-CT and DWI-MRI to assess the chemotherapy response.Result:There was no significant difference in CT value between the two groups.However,the difference of change rate of enhancement(AE%)was statistically significant(t=-5.623,p=0.000)in assessment of chemotherapy response,the area under the curve(AUC)was 0.903,95%confidence interval(Cl)was 0.789-1;when the cut-off value of AE%was-16.5%,the Youden index was 0.911,the sensitivity was 0.929 and the specificity was 0.882.Comparison of ADClocal and ADCentire among three time points showed significant difference in effective group(ADClocal,F=15.782,p?0.000;ADCentire,F=10.390,p=0.000)but no significant difference in ineffective group(ADClocal,F=2.828,p>0.05;ADCentire,F=1.183,P>0.05).The significant differences in ADClocal and ADCentire between the two groups were not found before chemotherapy but seen within 24-48 hours after first chemotherapy(ADClocal,t?3.689,p<0.05;ADCentire,t?3.381,p<0.05)and after 3 periods of chemotherapy(ADClocal,t=4.145,P<0.05;ADCentire,t=2.886,p<0.05).The ?DClocal%and ?ADCentire%also showed significant differences between the two groups after first chemotherapy(AADClocal,t=3.581,P<0.05;?ADCentire,t=2.537,P<0.05)and after 3 periods of chemotherapy(AADClocal,Z=-2.116,p<0.05;?ADCentire,Z=-2.006,p<0.05).The AUC of ?ADClocal%and ?ADCentire%in assessing chemotherapy response were 0.901(sensitivity 88.20%,specificity 82.90%)and 0.807(sensitivity 70.60%,specificity 92.90%)within 24-48 hours after first chemotherapy,and were 0.729(sensitivity 94.10%,specificity 64.30%)and 0.712(sensitivity 76.50%,specificity 28.60%)after 3 periods of chemotherapy.With combination of CE-CT and DWI-MRI,the sensitivity was 99.60%and the specificity was 56.70%.Conclusion:?E%and ADC value can assess the response of conversion therapy for unresectable gastric cancer.The ?ADC%even can predict treatment response as early as within 24-48 hours after first chemotherapy.A higher ?ADC means larger possibility of effective treatment.AADClocal%showed a better diagnostic efficiency than ?ADCentire%,while the combination of CE-CT and DWI-MRI could also improve the diagnostic efficiency.