Objective: 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.
Materials and methods: 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.
Results: 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).
Conclusion: 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.