Diffusion weighted magnetic resonance imaging of pre and post treatment nasopharyngeal carcinoma

Abstract

ObjectivesTo evaluate the utility of different Apparent Diffusion Coefficient (ADC) values on Diffused Weighted Magnetic Resonance Imaging (DW-MRI) for nasopharyngeal carcinoma (NPC). Study design and settingA retrospective cohort study in a single tertiary medical center. Subjects and methodsThe study group consists of patients with pathology proven NPC that underwent DW-MRI prior or/and following a non-surgical chemo radiation treatment between the years 2007 and 2017. ADC thresholds were analyzed and compared for primary (pre-treatment) and expected post-irradiation NPC cases and healthy controls. ResultsWe recruited 144 patients who underwent 195 MRI's for NPC. 25 DW-MRI were performed before (primary, active NPC) and 56 following (no residual NPC) treatment. 45 out of 225 patients who had brain DW-MRI for other reasons (control group) had measurable nasopharynx tissue (N = 33, adjusted for age and gender). The mean ADC of NPC prior to treatment (0.69 ± 0.13 × 10−3 mm2/s) was significantly lower (ANOVA, P < 0.001) compared to the mean ADC of the adjusted controls (1.11 ± 0.25 × 10−3 mm2/s) and post-treatment (1.49 ± 0.28 × 10−3 mm2/s) groups. An ADC threshold of 0.805 × 10−3 mm2/s had 94% and 93.9% sensitivity and specificity rates, respectively and an odds ratio of 175[95%CI(23.25–1000)], comparing ADC levels of pre-treatment NPC patients and adjusted control group. An ADC threshold of 0.965 × 10−3 mm2/s yielded 100% positive and negative predicted values distinguishing pre-treatment and post-treatment NPC patients (free of disease). There was no statistical association between ADC levels and tumor volume/stage, nodal stage or group staging. ConclusionsADC levels have distinct values in newly diagnosed and follow up of NPC.