Prostate cancer: the correlation between apparent diffusion coefficient values obtained from high resolution diffusion-weighted imaging and Gleason scores

Abstract

Objective To compare ADC values obtained from readout-segmented echo-planar imaging (RS-EPI) and single-shot echo-planar imaging (SS-EPI) techniques of prostate cancer and to investigate the correlation between RS-EPI ADC values and Gleason scores. Methods A retrospective analysis of RS-EPI and SS-EPI DWI were performed in 23 patients with pathologically confirmed prostate cancer. Routine MRI, RS-EPI DWI and SS-EPI DWI were obtained prior to ultrasound guided systemic biopsy in all cases. According to the location of lesion from biopsy report, a ROI was drawn on ADC map obtained from RS-EPI DWI and SS-EPI DWI, respectively, at cancerous foci with low T2WI and high DWI signal intensity. Foci were classified into well differentiated group (Gleason score≤6) and poorly and moderately differentiated group (Gleason score≥7). ADC values between RS-EPI and SS-EPI were compared by using t test. The relationship between ADC values and Gleason scores was assessed using Spearman test. The sensitivity and specificity of RS-EPI ADC value for differential diagnosis of two groups and the best cutoff were evaluated from ROC. Results Twenty nine well differentiated foci and 126 poorly and moderately differentiated foci were identified. The mean RS-EPI ADC value and the mean SS-EPI ADC value of well differentiated group and poorly and moderately differentiated group were (1.136 ± 0.136) × 10-3mm2/s, (1.125±0.198)×10-3mm2/s; (0.891±0.161)×10-3mm2/s, (0.875 ±0.184)×10-3mm2/s, respectively. Neither well differentiated group nor poorly and moderately differentiated group had a significant difference between the mean ADC value of two techniques (t values were 0.359 and 1.727, P values were 0.722 and 0.087, respectively). Either mean RS-EPI ADC value or mean SS-EPI ADC value between two groups had a significant difference (t values were 7.572 and 6.499, P<0.01, respectively). There was an inverse relationship between ADC values obtained from RS-EPI and SS-EPI and Gleason scores (r values were -0.638 and -0.565, P<0.01, respectively). When the cutoff value was 1.041×10-3mm2/s, the sensitivity and specificity of RS-EPI ADC value to differentiate two groups were 85.7% (108/126), 86.2% (25/29), respectively, and the area under ROC curve was 0.882. Conclusions There were no significant difference between ADC values obtained from RS-EPI and SS-EPI. ADC values of both techniques had positive correlation with Gleason scores. RS-EPI ADC values may have potential to allow noninvasive assessment of prostate cancer aggressiveness, which could help in the stratification of patients for appropriate therapy. Key words: Prostate neoplasms; Magnetic resonance imaging; Pathology