Diffusion-weighted Magnetic Resonance Imaging For Monitoring Early Treatment Response To Neoadjuvant Chemotherapy Of Nasopharyngeal Carcinoma

Objectives:To approach the value of clinical application of diffusion-weighted magnetic resonance imaging（DW-MRI）for monitoring early treatment response of neoadjuvant chemotherapy（NAC）of nasopharyngeal carcinoma,by comparing the change of apparent diffusion coefficient（ADC）values before and after treatment with gemcitabine or paclitaxel combined with platinum drugs.Methods:A total of 203 untreated patients with locally advanced nasopharyngeal carcinoma from September 2013 to December 2015 were enrolled.78 patients of them were treated with gemcitabine combined with platinum drugs（GEM group）,and 125 patients were treated paclitaxel combined with platinum drugs（PTX group）.Magnetic resonance scans were performed at baseline,the 4^th day,21^th day and 42^thh day after Neoadjuvant Chemotherapy initiated.At the end of the first and second cycle of NAC,all patients were classified into the responders（CR or PR）and non-responders（SD）according to the RECIST 1.1 guidelines.To compare and analyze the recent efficacy of patients in GEM and PTX groups by chi-square test.Forty patients were randomly selected from the GEM and PTX groups,and the ADC values of nasopharyngeal carcinoma at each time point were measured.Analyze ADC values at different points with repeated measures of variance.To analyze the ADC values,changes and change ratios of ADC values at each time point in different groups by an independent sample t-test or Mann-Whitney U test.The reliability of the parameters was evaluated by the receiver operating characteristic（ROC）curve.There was a significant difference between the two-sided test P<0.05.Results:At the end of the first cycle of chemotherapy,the overall efficacy of the GEM group was statistically higher than that of the PTX group（57.7%VS40.8%,χ2=5.498,P=0.019）.At the end of the second cycle of chemotherapy,the overall efficacy of the GEM group was statistically higher than that of the PTX group（78.2%VS 52.8%,χ2=13.235,P=0.000）.Combined with 33 patients in GEM group and 35 patients in the PTX group,at the end of the first cycle and the second cycle of NAC,the ADC_D21,ΔADC_D4,ΔADC_D21,%ADC_D4,and%ADC_D21 of responders were significantly larger than the non-effective groups（P<0.05）.In GEM group,at the end of the first and second cycle of chemotherapy,there was a significantly difference in ADC values,△ADC values,and%ADC on the 4th and21st days of chemotherapy between the effective and non-effective groups.In PTX group,at the end of the first cycle of chemotherapy,the effective group%ADC_D4,△ADC_D21 value and%ADC_D21 were significantly higher than the non-effective group（P<0.05）,at the end of the second cycle of chemotherapy,the ADC_D21,△ADC_D4,△ADC_D21,%ADC_D4and%ADC_D21 in the effective group were all higher than those in the non-effective group,and the difference was statistically significant（P<0.05）.According to the results of ROC curve,it was found that%ADC_D4≥15.30was used as a predictive threshold for the effective at end of the first cycle of chemotherapy in GEM group,with a sensitivity and specificity of 85%and 64.3%respectively;It was found that%ADC_D4≥14.87 was used as a predictive threshold for the effective at the end of the second cycle of chemotherapy in the GEM group,with a sensitivity and specificity of 80%and 75%respectively.It was found that%ADC_D4≥12.77 as,the sensitivity was 100%and the specificity was 56%.It was found that%ADC_D21≥16.89 as a predictive threshold for effective at the end of the second cycle of chemotherapy in PTX group,the sensitivity was 92.3%and the specificity was 83.3%.Conclusions:The△ADC_D4 value and%ADC_D4 were correlated with the early efficacy of neoadjuvant chemotherapy.Diffusion weighted imaging can be used to evaluate the recent efficacy of neoadjuvant chemotherapy in nasopharyngeal carcinoma,%ADC_D4 has a high sensitivity and specificity in the early evaluation of the therapeutic efficacy of GEM combined with platinum drugs;%ADC_D21 has a high sensitivity and specificity in the early evaluation of the therapeutic efficacy of PTX combined with platinum drugs.