Histogram Analysis Of Quantitative Parameters From Synthetic MRI:Value In The Assessment Of Prognostic Factors And Prediction Of Disease Progression In Nasopharyngeal Carcinoma

Part 1SyMRI combined with histogram analysis:Value in the assessment of prognostic factors in nasopharyngeal carcinomaObjectives:To evaluate the correlation between histogram parameters derived from synthetic magnetic resonance imaging（SyMRI）with prognostically relevant factors in nasopharyngeal carcinoma（NPC）.Method:Fifty-nine consecutive NPC patients were prospectively enrolled.Quantitative parameters（T1,T2 and proton density（PD））were obtained by outlining the threedimensional volume of interest（VOI）of all lesions.Then,histogram analysis of these quantitative parameters was performed and the correlations with prognostically relevant factors were assessed.By choosing appropriate cutoff,we divided the sample into two groups.Independent-samples t-test/Mann-Whitney U test was used and ROC curve analysis was further processed.Results:Histogram parameters of the T1,T2 and PD maps were positively correlated with the Ki-67 expression levels,and PD Mean was the most representative parameters（AUC:0.861）.The PD map exhibited good performance in differentiating epidermal growth factor receptor（EGFR）expression levels（AUC:0.706～0.732）and histological type（AUC:0.650～0.660）.T2_Minimum was highest correlated with Epstein-Barr virus（EBV）DNA levels（r=-0.419）,and PD₇5th Percentile exhibited the highest performance in distinguishing positive and negative EBV DNA groups（AUC:0.721）.T1_Minimum was statistically correlated with EA-IgA expression（r=-0.313）.Additionally,several histogram parameters were negatively correlated with tumor stage（T stage:r=-0.259～0.301;N stage:r=-0.348～-0.456;clinical stage:r=-0.419）.Conclusions:Histogram parameters of SyMRI could reflect tissue intrinsic characteristics and showed potential value in assessing the Ki-67 and EGFR expression level,histological type,EBV DNA level,EA-IgA and tumor stage.Part 2SyMRI combined with histogram analysis:Predictive value in disease progression of nasopharyngeal carcinomaObjectives:To investigate the potential of synthetic MRI（SyMRI）in the prognostic assessment of patients with nonmetastatic nasopharyngeal carcinoma（NPC）,and the predictive value when combined with diffusion weighted imaging（DWI）as well as Clinical factors.Methods:Fifty-three NPC patients underwent SyMRI were prospectively included.10th Percentile,Mean,Kurtosis and Skewness of T1,T2 and PD maps and ADC value were obtained from primary tumor.Cox regression analysis was used for analyzing the association between SyMRI and DWI parameters and progression-free survival（PFS）,then age,sex,staging and treatment as confounding factors were also included.C-index was obtained by bootstrap.Moreover,significant parameters were used to construct models in predicting 3-years disease progression.ROC curves and leave-one-out cross-validation were used to evaluate the performance and stability.Results:Disease progression occurred in 16（30.2%）patients at a follow-up of 39.6（3.5,48.2）months.T1_Kurtosis,T1_Skewness,T2₁0th,PD Mean and ADC were correlated with PFS,and T1_Kurtosis（HR:1.093）and ADC（HR:1.009）were independent predictors of PFS.The C-index of SyMRI and SyMRI+DWI+Clinic models were 0.687 and 0.779.Moreover,the SyMRI+DWI+Clinic model predicted 3-years disease progression better than DWI or Clinic model did（P≤0.008）.Interestingly,there was no significant difference between SyMRI model（AUC:0.748）and SyMRI+DWI+Clinic model（AUC:0.846,P=0.092）.Conclusion:SyMRI combined with histogram analysis could predict disease progression in NPC patients,and SyMRI+ DWI+ Clinic model further improve the predictive performance.