Application Of DWI In Evaluating The Response Of Brain Metastases Treated By Stereotactic Radiosurgery

Objective:Stereotactic therapeutic (SRS) has been applied to treat brain metastases. By measuring ADC and rADC of brain metastases before and early after SRS, our purpose was to see if ADC and rADC could be used to predict early therapeutic effect and provide more reliable information for clinician. Meanwhile, it is to assess if ADC and rADC have similar effect on evaluating the response of brain metastases treated by SRS and to confirm correlation between changes of tumor diameter and ADC value as well as rADC value.Methods:In a prospective study, we collected 26 brain metastases in 21 patients (10 men,11 women; mean age 59.6 years) treated in Gamma Knife Center during 2009.6～2010.12. Conventional MRI and DWI were taken one day before and 1 month, and 6 months after SRS. The ADCs of brain metastases and contralateral white matter and the max diameters of tumors were taken at the various time intervals, and tumor ADC values were normalized to normal-appearing white matter (rADC). All of the data was taken by GE AW 4.2 Functool II software. Mean ADC values and rADC values at each time point were compared with each other. Student t-test was applied to compare significant differences between these groups. Longitudinal changes of DWI parameters were analyzed by ANOVA test. Correlation between changes of tumor diameter and ADC value as well as rADC value was analyzed by Pearson's correlation test.Results:19 brain metastases were treated effectively.1 brain metastases was non-responsed.6 brain metastases were dead. The mean pretreatment ADC value and rADC value in these 19 brain metastases were 0.97±0.15×10-3mm2/s and 1.32±0.22 (mean±SD) respectively.1 month after SRS were 1.22±0.21×10-3mm2/s and 1.68±0.33.6 months after SRS were 1.36±0.26×10-3mm2/s and 1.86±0.38. Both of the values rose significantly (P<0.001) and the changes of ADC value and rADC value have no significant difference (P>0.05).1 tumor was progressive and both the ADC value and the rADC value declined after SRS.6 brain metastases were death when 1 month after treatment and the ADCs and the rADCs had no significant differences (P=0.861). Pearson's correlation test shows no significant correlation between changes of tumor diameter and ADC value in whole patients (rΔADC=0.20, P=0.40; rΔrADC=0.32, P=0.18).Conclusions:DWI is very meaningful in evaluating the early response of brain metastases treated by stereotactic radiosurgery. ADC value and rADC value of brain metastatic tumor might be useful to predict successful treatment at early time points. There is no significant correlation between changes of tumor diameter and ADC value or rADC value in whole patients. Both of ADC value and rADC value can be used to predict treatment effect.