Metastatic Diffusion Volume Based on Apparent Diffusion Coefficient as a Prognostic Factor in <scp>Castration‐Resistant</scp> Prostate Cancer

BACKGROUND Whole-body diffusion-weighted MRI (WB-DWI) is useful for assessing disease activity in castration-resistant prostate cancer (CRPC). MET-RADS-P is a subjective assessment-based reporting system proposed to standardize the interpretation of WB-DWI. However, a quantitative evaluation of WB-DWI has not been fully investigated. PURPOSE To investigate the validity, and analyze the prognostic value, of quantitative evaluation of WB-DWI based on apparent diffusion coefficient (ADC) values for CRPC. STUDY TYPE Retrospective. POPULATION Sixty-six patients with CRPC. The median age was 75 years. During the median follow-up period of 25.2 months, 23 of 66 patients (34.8%) died of prostate cancer. FIELD STRENGTH/SEQUENCE A 1.5 T WB-DWI was used with two b-values (0 s/mm2 -1000 s/mm2 ). A single-shot echo-planar imaging sequence was used. ASSESSMENT WB-DWI were evaluated by three readers according to MET-RADS-P scoring system. Using imaging software, Attractive BDScore, tumor diffusion volume (mDV) and ADC value of metastatic lesion (mADC) was calculated by two readers. The mDV was calculated with ADC values (&#215;10-3 mm2 /sec) of 0.4-0.9 (mDV0.4-0.9 ), 0.9-1.4 (mDV0.9-1.4 ), and 1.4-1.8 (mDV1.4-1.8 ), respectively. STATISTICAL TESTS Spearman&#39;s rank correlation coefficient was used to assess the correlation. The relationships between the variables with cancer-specific survival (CSS) were evaluated. Multivariate analysis was performed using the Cox proportional hazards model. RESULTS mDVs showed a strong positive correlation with MET-RADS-P scores (r = 0.90/0.87, P