Diffusion-weighted MRI in early assessment of tumour response to radiotherapy in high-risk prostate cancer.

Abstract

The objective of this study was to assess the efficacy of diffusion-weighted MRI (DWI) in monitoring response to radiotherapy in high-risk prostate cancer (PC). This retrospective study included 78 patients with high-risk PC undergoing 3.0-T MRI (supplemented by DWI) before and after intensity-modulated radiotherapy (IMRT). Based on follow-up clinical examinations, patients were divided into two groups: the recurrence group (patients who suffered biochemical/clinical recurrence within 3 years, n = 13) and the non-recurrence group (patients who were recurrence free for over 3 years, n = 65). The apparent diffusion coefficient (ADC) values before and after IMRT were compared between these two groups. The receiver-operating characteristics (ROC) analysis was carried out to investigate the discriminatory capability for pre- and post-IMRT ADC values. The overall ADC values were 1.04 ± 0.18 × 10(-3) mm(2) s(-1) for PCs before IMRT and 1.45 ± 0.15 × 10(-3) mm(2) s(-1) after IMRT (p < 0.001). A statistically significant difference in post-IMRT ADC values was noted between patients with and without recurrence (1.27 ± 0.14 × 10(-3) mm(2) s(-1) vs 1.49 ± 0.12 × 10(-3)mm(2) s(-1); p < 0.001), although there was no statistical difference between them in pre-IMRT ADC values (1.00 ± 0.17 × 10(-3) mm(2) s(-1) vs 1.05 ± 0.18 × 10(-3) mm(2) s(-1); p = 0.31). The ROC curve analysis revealed that the post-IMRT ADC values could help identify patients suffering recurrences (area under the curve, 0.88; p < 0.001). Marked increase in ADC values was observed in PC after radiotherapy, especially in good responders. DWI is a valuable tool for monitoring the response to radiotherapy. This study examined the relationship between ADC changes and tumour response to treatment of PC.