Intravoxel Incoherent Motion Imaging In Evaluating The Response Of Breast Cancers To The Neoadjuvant Chemotherapy

Objective:To assess the value of intravoxel incoherent motion(IVIM)in evaluating the response of breast cancers to the neoadjuvant chemotherapy(NAC).Methods:Sixty patients,who underwent neoadjuvant chemotherapy and subsequent surgery,were prospectively recruited.All patients underwent MRI(including IVIM imaging)for three times:before NAC(T1),after the first cycle of NAC(T2)and after full cycles of NAC(T3).The values of apparent diffusion coefficient(ADC),pure diffusion coefficient(D),pseudo-diffusion coefficient(D*)and perfusion fraction(f)were measured.According to Miller-Payne Grading of pathology from surgery,patients were divided into good(R group)and mild response group(NR group).The t test of two independent samples and Mann-Whitney U test were used to compare the parameters at the three time points between groups and to compare the T2-T1 parameter difference(△ADC、△D*、△D、△f)between groups.The paired sample t test and Wilcoxon rank sum test were used to compare the parameters from T2 or T3 with those from T1,respectively.For parameters with statistically significant inter-group difference,ROC analysis was used.Results:There were 21 cases in the R group and 40 cases in NR group.At T2,the f value of R group was significantly lower than that of NR group(P=0.027);However,ADC and D values had no significant difference between groups.At T3,ADC and D values of R group were significantly higher than those of NR group(P=0.002,0.000,respectively);The f value of R group was significantly lower than that of NR group(P=0.000).D*value showed no inter-group difference at both T2 and T3.The differences of △D、△f values between groups were statistically significant(P=0.001,0.000,respectively),however,△ADC and △D*was not statistically different between groups.Further intra-group comparison showed that f,D and ADC values of the R group were significantly changed,no matter at T2 or T3,compared with T1.However,in NR group,only the D value at T3 significantly changed when compared with T1(P=0.010).The areas under the ROC curve of f,Af and AD value were 0.673,0.788,0.753,with no significant difference among them.Conclusions:IVIM may be a useful adjunctive tool in evaluating the reponse of tumors to NAC.The f and D have the potential of both early prediction and end-NAC evaluation,while ADC is helpful only in end-NAC evaluation.D*has no value.