Intensity of stromal changes predicts biochemical recurrence-free survival in prostatic carcinoma

Abstract

Objective: The objective of our study was to determine the relationship between the apparent diffusion coefficient (ADC) value on diffusion-weighted imaging (DWI) and Gleason score of prostate cancer and percentage of tumor involvement on prostate core biopsy. Materials and Methods: We performed a retrospective study of 57 patients with biopsy-proven prostate cancer who underwent endorectal MRI with DWI between July 2007 and March 2008. Regions of interest (ROIs) were drawn on ADC maps at sites of visible tumor on DW images and ADC maps. A hierarchic mixed linear model was used to compare the ADC value of prostate cancer with the Gleason score and the percentage of tumor on core biopsy. Results: Eighty-one sites of biopsy-proven prostate cancer were visible on DW images and ADC maps. The least-squares mean ADC for disease with a Gleason score of 6 was 0.860 x 10(-3) mm(2)/s (standard error of the mean [SEM], 0.036); Gleason score of 7, 0.702 x 10(-3) mm(2)/s (SEM, 0.030); Gleason score of 8, 0.672 x 10(-3) mm(2)/s (SEM, 0.057); and Gleason score of 9, 0.686 x 10(-3) mm(2)/s (SEM, 0.067). Differences between the mean ADC values for a prostate tumor with a Gleason score of 6 and one with a Gleason score of 7 (p = 0.0096) and for a prostate tumor with a Gleason score of 6 and one with a Gleason score of 8 (p = 0.0460) were significant. Comparison between the ADC and percentage of tumor on core biopsy showed a mean ADC decrease of 0.006 (range, 0.004-0.008 x 10(-3) mm(2)/s) for every 1% increase in tumor in the core biopsy specimen. Conclusion: DWI may help differentiate between low-risk (Gleason score, 6) and intermediate-risk (Gleason score, 7) prostate cancer and between low-risk (Gleason score, 6) and high-risk (Gleason score > 7) prostate cancer. There is an inverse relationship between the ADC and the percentage of tumor involvement on prostate core biopsies. Editorial CommentIn prostate cancer occurs significant reduction in the diffusion properties of water protons thus resulting in a reduction in the measured apparent diffusion coefficient (ADC) value relative to normal prostatic tissue. Several reports have been showing the utility of this technique. The combination of anatomic information obtained with conventional T2-weighted image with functional information, obtained with diffusion-weighted image, offers significant advantage over the use of either one of these techniques separately. This association significantly improves cancer detection and the accuracy in predicting the volume of cancer of the peripheral zone. This combined technique however is more effective in tumors larger than 0.5 cm3.In this publication the authors show that the ADC values of prostate cancer may help differentiate between low-risk (Gleason, 6) and intermediate-risk (Gleason score 7 disease and between low-risk and high-risk (Gleason> 7). The ADC values in this study were compared with results of prostate biopsy. In other words, higher cellular density found in poorly differentiated tumors is responsible for more restricted m...