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 − 3 mm 2 /s) of 0.4–1.0 and 1.0–1.8 (× 10 − 3 mm 2 /s), mDV with ADC values (× 10 − 3 mm 2 /s) of 0.4–1.0 (mDV 0.4−1.0 ) showed a more favorable association with CFS compared to total mDV. On multivariate analysis, mDV 0.4−1.0 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 − 3 mm 2 /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.