Assessing Early Response Of Esophageal Squamous Cell Carcinoma Under Chemoradiotherapy By Intravoxel Incoherent Motion Magnetic Resonance Imaging

Objective:The objective of this study was to explore the feasibility of intravoxel incoherent motion(IVIM)magnetic resonance(MR)imaging in the early assessment of treatment response to definitive concurrent CRT.Methods and Materials:23 inoperable ESCC's patients were prospectively enrolled in this study.All patients performed IVIM MR imaging at 4 time points:pre-CRT(within 5 days before CRT),mid-CRT(2?3 weeks after the start of CRT,radiotherapy to 15 fractions,30Gy),end-CRT(within 5 days after the end of CRT)and post-CRT(one month after the end of CRT).IVIM sequence included 9 b values(0,25,50,75,100,150,200,500 and 800 s/mm2).The diffusion coefficient(D),perfusion fraction(f)and pseudo-diffusion coefficient(D*)were calculated with a bi-exponential model and apparent diffusion coefficient(ADC)was obtained by a mono-exponential model,respectively.All MR images were analyzed independently by 2 radiologists and treatment response was assessed by Response Evaluation Criteria in Solid Tumors(RECIST).Analyses of variance for repeated measurements were conducted to observe dynamic changes of IVIM-based parameters and ADC during CRT.The parameters and their change percentages(?%)were compared between complete response(CR)and partial response(PR)by Mann-Whitney U-test.Diagnostic performance of parameters in predicting early response was tested with receiver operating characteristic curve analysis.RESULTS:Among 23 patients,15(65.2%)patients showed CR to CRT while 8(34.8%)patients achieved PR atfter treament.ADC,D and of the lesions increased significantly during CRT(P<0.001,<0.001 and 0.001,respectively).ADC,f,?%ADC and ?%D at mid-CRT(radiotherapy to 15 fractions,30Gy)in CR group were significantly higher than those in PR group(P = 0.002,0.013,0.005 and 0.011,respectively).D combined with f and ADC had the highest predictive value in identifying CR from PR,yielding area under curve(AUC)of 0.917(P<0.001).CONCLUSION:IVIM parameters proved useful in assessing response to definitive concurrent CRT for inoperable ESCC and combined with ADC at an early stage of treatment was a good predictor of response.