Background: Abnormal microangiogenesis and microenvironmental disturbances within the Nasopharyngeal carcinoma (NPC) can exacerbate tumor hypoxia, which may increase radiotherapy resistance and thus lead to poor prognosis in NPC patients. A non-invasive imaging technique, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), which can reflect the tumor blood perfusion and angiogenesis status, was used to investigate the relationships of DCE-MRI parameters with hypoxia-inducible factor 1 alpha (HIF-1α) expression and tumor grades in NPC patients.
Methods: 42 treatment-naive patients with pathologically confirmed NPC were enrolled in this analysis. Plain magnetic resonance scans and DCE-MRI scans were performed before treatment, and post-processing was performed to calculate the relative enhancement (RE), maximum relative enhancement (MRE), maximum enhancement (ME), wash-in rate (WIR), wash-out rate (WOR), time to peak (TTP), and area under the curve (AUC). Immunohistochemistry was used to detect HIF-1α expression in electronasopharyngeal fiberoscopic specimens. The clinical grade/stage of NPC was jointly assessed by an experienced radiologist and a radiotherapist. The potential correlations of the DCE-MRI parameters with HIF-1α expression and clinical grades were analyzed. The statistical analysis was performed using SPSS 17.0 software package.
Results: Among DCE-MRI parameters, RE, ME, and MRE were associated with the positive expression of HIF-lα in NPC and could reflect the hypoxic status in the local microenvironment of the cancer foci in vivo. RE, ME, and MRE were significantly higher in the positive HIF-1α expression group than in the negative HIF-1α expression group (F=5.281, P=0.027; F=11.923, P=0.001; F=6.228, P=0.017). RE, ME, and MRE were significantly correlated with clinical grade (F=3.646, P=0.021; F=3.204, P=0.034, F=3.050, P=0.040) and T stage (F=6.578, P=0.001; F=3.540, P=0.023; F=4.384, P=0.010). The values of RE, MRE, and ME gradually increased as the clinical grade and T stage increased.
Conclusions: DCE-MRI is a valuable imaging technique for the noninvasive evaluation of hypoxia in NPC, the development of individualized treatment protocols, and the prediction of efficacy.
Keywords: Nasopharyngeal carcinoma (NPC); dynamic contrast-enhanced (DCE); hypoxia-inducible factor 1 alpha (HIF-1α); magnetic resonance imaging (MRI).