Value of diffusion-weighted imaging at 3 T for prediction of extracapsular extension in patients with prostate cancer: a preliminary study.

Abstract

The purpose of this study was to retrospectively investigate the value of adding diffusion-weighted imaging (DWI) to T2-weighted imaging for the prediction of extracapsular extension (ECE) in patients with prostate cancer, as well as to compare apparent diffusion coefficients (ADCs) between patients with and without ECE. Seventy-six patients with suspected prostate cancer underwent T2-weighted imaging and DWI at 3 T using a phased-array coil, followed by radical prostatectomy. For prediction of ECE, the prostate was divided into six sectors. Two experienced radiologists analyzed T2-weighted images alone and in combination with DWI in consensus and rated the likelihood of ECE on a five-point scale. Tumor ADC values were measured, and the results were compared between patients with and without ECE. Of the 456 sectors studied, 74 (16%) were positive for ECE in 31 patients. For prediction of ECE, the specificity and accuracy of combined T2-weighted imaging and DWI were 94.5% and 91.7%, respectively, superior to those of T2-weighted imaging alone (87.2% and 81.2%, respectively) (p < 0.001). On receiver operating characteristic analysis, the area under the curve (Az) of combined T2-weighted imaging and DWI (Az = 0.900) was significantly greater than that of T2-weighted imaging alone (Az = 0.828) (p < 0.001). The mean tumor ADC values were significantly lower in patients with ECE than patients without ECE (p < 0.001). DWI at 3 T in addition to T2-weighted imaging improves the ability to predict ECE in patients with prostate cancer. Furthermore, tumor ADC values in patients with and without ECE are significantly different.