3152 Background: Robust methods are needed that can monitor patients (pts) being treated with AA in a clinical environment. While DCE-MRI is an effective method for monitoring the PDE of AA (ASCO 22, 824, 2003), different methods are used to acquire and then analyze the data obtained. Administration of an MRI contrast agent (COA) allows the visualization of the vasculature into which that solute distributes, and using a fast acquisition method, one monitors the rate of influx of blood into tumor and other organs, as well as the retention and the rate of efflux. We believe that high temporal resolution (e.g. 1 second) is critical to capture the early influx phase, which appears to be most critically associated with pt response. Methods: Upon COA administration as a bolus (1 ml Gd-DTPA/10 lbs of pt-weight, at 2 ml/sec), MR images are acquired using a volume sequence with a temporal resolution of 1 sec for the first 2 min, followed by data acquisition every 15–30 sec for another 20 min. Data analysis is performed by a direct measurement of the time course of proton enhancement using ImageJ, an image analysis software developed at the NIH (http://rsb.info.nih.gov/ij) and estimating the changes in the rates of the influx (ICAR, Initial Contrast Accumulation Rate) and of the efflux (DCAR, Delayed Contrast Accumulation Rate) in any desired Region-of-Interest. Prior alternative methods relied on the AUC and compartmental analyses (COMP) approaches. Results: The association between the change in the ICAR in pts treated with Taxotere and response, time-to-progression and survival was p=0.006, 0.006 and 0.02, respectively. In a representative patient the ICAR values of 6 slices were 9.8±1.75 and the ratio of k12/k21 were 9.5±0.63. Detailed comparisons of analyses between the ICAR and COMP will be presented. Conclusions: While both ICAR and COMP provide statistically valid data, the ICAR slope change provides an effective, robust and reliable method that should be used in monitoring pts for PDE of AA. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration AstraZeneca; Aventis