Is apparent diffusion coefficient reliable and accurate for monitoring effects of antiangiogenic treatment in a longitudinal study?

Purpose: To evaluate the reliability and accuracy of the apparent diffusion coefficient (ADC) for monitoring antiangiogenic treatment in a longitudinal study. Materials and Methods: Tumor volume and ADC were monitored by T2-weighted magnetic resonance imaging (MRI) and diffusion-weighted MRI, respectively, in 18 mice with angiogenesis-dependent tumors (U118MG) before (day 0) and after 2, 7, 14, and 21 days of administration of the antiangiogenic agent sunitinib maleate (n = 12) or vehicle (n = 6). Percent changes in tumor volume and ADC were calculated and correlations between tumor volume and ADC were evaluated. Results: Tumor volume and ADC showed a negative correlation at 69 of the 72 (96%) follow-up measurements. In the 13 mice with tumor regrowth, ADC started to decrease before (27%) or at the same time (73%) as tumor regrowth. Pretreatment ADC and percent change in ADC change on days 02 were similar in mice with positive and negative responses to treatment (0.851 vs. 0.999, 24% vs. 16%). Percent change of ADC showed significant negative correlation with percent change in tumor volume in both the control (r = -0.69) and treated (r = -0.65) groups. Conclusion: Percent change in ADC is a reliable and accurate marker for monitoring the effects of antiangiogenic treatment, whereas pretreatment ADC and early changes in ADC (ie, days 02) are limited in predicting treatment outcome. J. Magn. Reson. Imaging 2012;. (c) 2012 Wiley Periodicals, Inc.