Diffusion-Weighted MR Imaging Derived Apparent Diffusion Coefficient Is Predictive of Clinical Outcome in Primary Central Nervous System

BACKGROUND AND PURPOSE: There is evidence that increased tumor cellular attenuation within diagnostic specimens of primary central nervous system lymphoma (PCNSL) may have significant prognostic implications. Because cellular attenuation may influence measurements of apparent diffusion coefficient (ADC) by using diffusion-weighted MR imaging (DWI), we hypothesized that ADC measured from contrast-enhancing regions might correlate with clinical outcome in patients with PCNSL. MATERIALS AND METHODS: PCNSL tumors from 18 immunocompetent patients, treated uniformly with methotrexate-based chemotherapy, were studied with pretherapeutic DWI. Enhancing lesions were diagnosed by pathologic analysis as high-grade B-cell lymphomas. Regions of interest were placed around all enhancing lesions allowing calculation of mean, 25th percentile (ADC25%), and minimum ADC values. Histopathologic tumor cellularity was quantitatively measured in all patients. High and low ADC groups were stratified by the median ADC value of the cohort. TheWelch t test assessed differences between groups. The Pearson correlation examined relationships between ADCmeasurements and tumor cellular attenuation. Single and multivariable survival analysis was performed. RESULTS: We detected significant intra- and intertumor heterogeneity in ADC measurements. An inverse correlation between cellular attenuation and ADC measurements was observed (P .05)