Prostate and metastasis diffusion volume based on apparent diffusion coefficient as a prognostic factor in Hormone-naïve prostate Cancer.

In this study, to assess the utility of whole-body DWI (WB-DWI) as an imaging biomarker for metastatic hormone-naïve prostate cancer (mHNPC), we evaluated tumor diffusion volume based on apparent diffusion coefficient (ADC) values. WB-DWI results obtained from 62 mHNPC patients were evaluated in this retrospective analysis. The association with castration resistant-free survival (CFS) was evaluated for both prostate and metastatic tumor diffusion volume (pDV and mDV, respectively) based on WB-DWI. The usefulness of pDV and mDV based on ADC values to predict CFS was also examined. During the follow-up period, 22 patients progressed to castration-resistant prostate cancer, and the median CFS was 42.6 months. The median mDV and pDV were 6.7 and 12.6 mL, respectively. mDV was a significant predictor of CFS (hazard ratio [HR]: 2.75; p = 0.022), while pDV was not significant. When DV was divided into groups by ADC values (× 10 mm/s) of 0.4-1.0 and 1.0-1.8 (× 10 mm/s), mDV with ADC values (× 10 mm/s) of 0.4-1.0 (mDV) showed a more favorable association with CFS compared to total mDV. On multivariate analysis, mDV and Gleason grade group had a statistically significant association with CFS (HR: 4.0; p = 0.004, and HR: 3.4; p = 0.006, respectively), while pDV with ADC values (× 10 mm/s) of 0.4-1.0 did not have a significant association. mDV is useful for predicting CFS in mHNPC patients. mDV may be a better imaging biomarker when based on ADC values.