Changes in diffusion-weighted images for visualizing prostate cancer during antiandrogen therapy: preliminary results.

Objectives: To assess the potential of diffusion-weighted imaging (DWI) for monitoring the response to antiandrogen therapy in prostate cancer.

Methods: After patients had undergone 6 months of antiandrogen therapy, we investigated the time-course changes in findings obtained from DWI compared to the findings obtained from T(2)-weighted (T(2)W) images, transrectal ultrasound (TRUS), and prostate-specific antigen (PSA) kinetics.

Results: The time-course changes in T(2)W images, TRUS, and PSA kinetics following antiandrogen therapy in the present study were consistent with previous reports. In all patients, the posttreatment hypointense signals on DWI were attenuated. Identification of tumor location was difficult on the basis of changes in magnetic resonance imaging findings following antiandrogen therapy due to the remarkable reduction of the total prostatic volume. Three patients exhibited residual tumors that were easily visualized, and apparent diffusion coefficient values increased after treatment in these patients. However, in 1 patient with neuroendocrine differentiation during antiandrogen therapy, DWI findings revealed that the hypointense signal in the prostate became progressively more pronounced. However, this case showed a low PSA recurrence without remarkable changes in the T(2)W images.

Conclusions: The preliminary results suggest that DWI is useful to understand clinical significance of PSA kinetics in patients with low PSA recurrence during antiandrogen therapy.