Prediction Of Residual Lymph Nodes After Radiotherapy In Nasopharyngeal Carcinoma Patients With The Change Of Adc (apparent Difusion Coefficient) Value

Objective To evaluate the value of diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) for predicting residual metastatic lymph nodes after radiotherapy in primary nasopharyngeal carcinoma patients. The threshold of apparent diffusion coefficient (ADC) for predicting residual metastatic lymph nodes after radiotherapy in primary nasopharyngeal carcinoma patients was established .Methods From march 2009 to october 2010,36 primary nasopharyngeal carcinoma patients received WB-DWI scan during their hospitalization, The apparent diffusion coefficient (ADC) values of cervical metastatic lymph nodes were detected before these patients received treatment and after two weeks of radiotherapy. 56 cervical metastatic lymph nodes'ADC values were detected in this study. The value of"R"is defined by the difference of the second ADC values and the first ADC values. The cut-off value of the"R"was found by using receiver operating characteristic (ROC) curve analysis.56 value of"R"were divided into two groups by the cut-off value of the"R", Chi-Square test was used to compare their rates of residual metastatic lymph nodes after radiotherapy. Regression analysis for the value of"R",sex,age and the size of cervical metastatic lymph nodes was performed by using logistic regression model.Results the mean of residual metastatic lymph nodes'value of"R"was significantly lower than the mean of non-residual metastatic lymph nodes'value of"R"(P=0.000<0.001) . The cut-off value of the"R"was found by using receiver operating characteristic (ROC) curve analysis, the AUC is 0.895. When a value of the"R"of 0.1965 was used for threshold, the sensitiity was 64.7%, with specificity 97.4%. 56 value of"R"were divided into two groups by the cut-off value of the"R", the rates of residual metastatic lymph nodes after radiotherapy of two groups were significantly different (χ2 =23.59, P=0.000<0.001).Regression analysis for the value of"R"showed : a negitive correlation was found between the possibility of cervical metastatic lymph nodes'residual after radiotherapy and the value of"R".Conclusions The value of"R"can predict cervical metastatic lymph nodes'residual after radiotherapy to a certain extent.