Predicting and monitoring response to chemotherapy by 1,3-bis(2-chloroethyl)-1-nitrosourea in subcutaneously implanted 9L glioma using the apparent diffusion coefficient of water and23Na MRI

Purpose To examine the effects of the alkylating anticancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) on 23Na MRI and the water apparent diffusion coefficient (ADC) in subcutaneously- (sc-) implanted 9L glioma in rats. Materials and Methods 23Na MRI and 1H water ADC measurements were performed on sham-treated control (N = 6) and BCNU-treated (N = 15) Fisher rats one day before BCNU injection and then one, three, and five days after BCNU injection. Results The BCNU-treated tumors were divided into BCNU-responsive (RBCNU) and BCNU-nonresponsive (NRBCNU) groups depending on the tumor volume changes that occurred after therapy. The pretreatment 23Na MRI signal intensity (SI) and water ADC values were higher in RBCNU tumors compared to NRBCNU tumors. 23Na MRI SI and water ADC increased with tumor growth in control and NRBCNU groups, but these changes were interrupted by BCNU therapy in RBCNU group. Conclusion 23Na MRI and water ADC measurements may be useful for predicting and monitoring response to chemotherapy in some tumors. However, the changes that occurred in 23Na MRI SI and water ADC in sc-implanted 9L tumors are in contrast to previously published results for BCNU therapy of orthotopic 9L tumors. This may have important implications for monitoring therapy response in tumors. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.