Diffusion-weighted Magnetic Resonance Imaging For Monitoring Early Treatment Response To Chemoradiotherapy Of Nasopharyngeal Carcinoma

PURPOSE：To prospectively evaluate the feasibility of Diffusion-weighted magneticresonance imaging (DW-MRI) for monitoring early treatment response toChemoradiotherapy (CRT) of Nasopharyngeal Carcinoma (NPC).METHOD AND MATERIALS：Seventy-five patients with stage III and IV NPCwere enrolled and randomly assigned to two groups in this study from February2012to July2013．Diffusion-weighted sequences with diffusion factor of0and800mm2/swere performed using a3.0T Philips Achieva TX scanner at baseline,3days,20days(group1only)/42days (group2only) after Neoadjuvant Chemotherapy (NAC)initiated and at the end of chemoradiotherapy initiation (radiotherapy terminated). Thetumor size before and after21/42days after NAC initiated was measured andclassified into responders and non-responders based on RECIST1.1. At the end ofCRT, the tumors were regrouped into complete remission (CR) and residual disease.The apparent diffusion coefficient (ADC) values and their changes at each time pointwere compared between all different outcome groups using dependent-samples t test.The parameters with optimal time point to detect the tumor response to therapy werechosen. Receiver operating characteristics (ROC) analysis and logistic regressionmodel were performed in order to evaluate the feasibility of the chosen parameters inmonitoring early treatment response.RESULTS：The ADC values, ADC changes (ΔADC) and percentage ADC changes(Δ%ADC) of day20in responders were significantly higher than in non-responders(P<0.05) for group1(day20). At the end of CRT, responders from group1(day20) allachieved CR while responders from group2(day42) have two residual lesions. TheΔADC and Δ%ADC of day3in patients with CR were significantly higher than inpatients with residual tumor (P=0.007; P=0.005, respectively). When ΔADC (day3)≤0.099×10-3mm2/s was used for threshold, the sensitivity was79.6％, with specificity73.7％. There was a negative correlation between the possibility of residual tumor andΔADC (day3) after CRT(β=-8.426，P=0.047)．CONCLUSION：DW-MRI with ADC change allows for detecting early treatmentresponse of NPC and provides the opportunity to adjust following CRT regimen.20days after NAC initiated might be the optimal time for monitoring NACresponse.ADC changes3days after NAC initiated was a potential imaging predictorfor CRT in NPC.