Induction chemotherapy (IC) is an effective way to control subclinical metastasis in locally-advanced nasopharyngeal cancer patients. If the outcome can be predicted at an early stage of the treatment, the patient could be spared from unnecessary treatment toxicity. In this light, the aim of the present study is to find appropriate metrics for assessing the response of Adenopathy through quantification of the heterogeneity in diffusion-weighted images (DWI) of lymph nodes (LN) early after initiation of chemotherapy.^1,2,3The study group consisted of 7 patients. DWI was performed before and ten days after the initiation of injection in the first cycle of induction chemotherapy on 1.5T Avanto Siemens scanner. Patient characteristics and imaging parameters are demonstrated in Tables 1 and 2. Apparent diffusion coefficient (ADC) maps were generated from DW images on the system workstation. LNs, diagnosed as malignant on pre-therapeutic clinical and imaging assessment, were included for response assessment. Regions of interest (ROIs) containing the malignant LNs were delineated on the ADC-maps and Gd-enhanced T1-weighted images for each patient at two different time points. The LN volumes were calculated for the selected area on T1C images. Several commonly-used quantitative parameters, including mean-, max-, min-, and median-ADC were calculated for the defined ROIs on ADC-maps. Moreover, first-order histogram analysis was applied on the ROIs to derive the following features: (1) histogram standard deviation, representing average contrast, (2) normalized variance, as a measure of smoothness, (3) skewness, denoting the third moment, (4) energy, as a measure of uniformity or homogeneity, and (5) entropy, a statistical measure of irregularities of ADC-values.For each quantitative parameter, differences between two time-points were compared with Wilcoxon non-parametric test. A level of p-value less than 0.05 was regarded as statistically significant. As indicated in Table 3, mean, median, smoothness, third moment and uniformity indicate statistically significant difference (p-value< 0.05) for early changes of LN structures following induction chemotherapy. No significant change was observed in the volume of LNs (p-value = 0.128). Uniformity metric decreased in the second time-point (after IC) for all patients.For nasopharyngeal patients with involved LN, the standard determination of the response of LN is based on conventional MRI. In this study, histogram analysis was carried out in manually-defined ROIs selected within the tumor on ADC-maps to reveal physiological alterations early after IC. For this purpose, several quantitative metrics derived from ADC-map were explored to obtain the most accurate feature(s) as potential predictive biomarker(s) for early response of the lymph node to IC. The initial results showed that mean, smoothness, third moment and uniformity metrics, which are indicators of heterogeneity, could detect early response of the lymph node to treatment. This is in the meantime that the volume of the lymph nodes could not exhibit significant differences (p-value=: 0.128) for early response assessment. Finally, the results reported in this abstract will be validated in a larger patient population to determine the optimum heterogeneity features that can be adopted as relevant biomarkers for response assessment of lymph nodes to IC. Furthermore, serial DWI will be acquired to find correlation between changes of extracted heterogeneity metrics and the tumor residue after completion of the IC. .