Relationships Between Primary Lesion’s ADC Value Of Locally Advanced Nasopharyngeal Carcinoma And Pathological Indices

Background and Purpose: Certain relationships exist betweenapparent diffusion coefficient（ADC） value and the radiotherapeuticeffect of many tumors. Our previous study revealed that ADCvariation of nasopharyngeal carcinoma（NPC） was highly correlatedwith short-term therapeutic effect. The exact mechanism, however,still remains uncertain. To further investigate the pathologicalmechanism of primary lesion’s ADC variation of NPC, we analyze thecorrelations between ADC value of patients with NPC and the celldensity, microvessel density and nuclear proliferation index.Materials and Methods Patients with locally advanced NPC whowere treated with intensity modulated radiation therapy between April2010and November2011were involved in this study．Conventionaland DWI MRI scans （diffusion factor of0and800s/mm²） wereperformed at two time points: before radiotherapy and duringradiotherapy（just two weeks thereafter）. The ADC values of theprimary lesion were measured then. Histological specimens were dealtwith hematoxylin and eosin staining and immunohistochemicalstaining.The cell density, microvessel density and nuclearproliferation index values of the primary lesions were counted.Finally, The relationships between the ADC value beforeradiotherapy, the ADC difference between the two time point andthose three pathology indices were analysed by correlation analysisi．Results:79patients were eligible for our study, of whom33cases belonged to T3stage, and46cases to T4stage．The average ADCvalues of primary lesion before radiotherapy and two were from thebeginning of radiotherapy were （8.15±1.28）x10^-4mm²/s(min5.24x10^-4---max12.1x10^-4) and（13.32±2.44）x10^-4mm²/s (min9.1x10^-4-max19.4x10^-4) respectively. The average values of cell density,microvessel density and nuclear proliferation index were54±19percent（min4-max88）,66.46±23.94（min18-max116）and6.89±3.18（mi n0---max12）per high power field respectively. Thereare not significant correlations between the ADC values beforeradiotherapy and the cell density, microvessel density and nuclearproliferation index values（P values were0.896,0.517,0.201respectively）. There is negative correlation between the ADC valuedifference and the cell density （r=-0.426， P=0.001<0.001）, andpositive correlation between the ADC value difference andmicrovessel density（r=0.429， P<0.001）. However, there is notsignificant correlation between the ADC value difference and nuclearproliferation index（P=0.820>0.05）. Linear correlations exist betweenADC values before radiotherapy and ages and T stages. Linearcorrelations also exist between ADC value differences and ages, thecell density, microvessel density. The ADC value differences reflectthe cell density, microvessel density indirectly. The larger thedifference is, the smaller the cell density is and the larger themicrovessel density is.Conclusion ADC variation of NPC may have corelation with the celldensity and the microvessel density, which provide pathologicalmechanism for ADC value using to predict the prognosis ofnasopharyngeal carcinoma received radiotherapy.