Multiparametric MRI as a Biomarker of Response to Neoadjuvant Therapy for Localized Prostate Cancer–A Pilot Study

Rationale and Objectives: To explore a role for multiparametric MRI (mpMRI) as a biomarker of response to neoadjuvant androgen deprivation therapy (ADD for prostate cancer (PCa).Materials and Methods: This prospective study was approved by the institutional review board and was HIPAA compliant. Eight patients with localized PCa had a baseline mpMRI, repeated after 6-months of ADT, followed by prostatectomy. mpMRl indices were extracted from tumor and normal regions of interest (TROT/NROI). Residual cancer burden (RCB) was measured on mpMRl and on the prostatectomy specimen. Paired t-tests compared TROI/NROI mpMRI indices and pre/post-treatment TROI mpMRI indices. Spearman's rank tested for correlations between MRI/pathology-based RCB, and between pathological RCB and mpMRl indices.Results: At baseline, TROI apparent diffusion coefficient (ADC) was lower and dynamic contrast enhanced (DCE) metrics were higher, compared to NROI (ADC: 806 +/- 137 x 10(-6) vs. 1277 +/- 213 x 10(-6) mm(2)/sec, p = 0.0005; K-trans: 0.346 +/- 0.16 vs. 0.144 +/- 0.06 min(-1), p = 0.002; AUC(90): 0.213 +/- 0.08 vs. 0.11 +/- 0.03, p = 0.002). Post-treatment, there was no change in TROT ADC, but a decrease in TROI K-trans (0.346 +/- 0.16 to 0.188 +/- 0.08 min(-1); p = 0.02) and AUC(90) (0.213 +/- 0.08 to 0.13 +/- 0.06; p = 0.02). Tumor volume decreased with ADT. There was no difference between mpMRl-based and pathology-based RCB, which positively correlated (p = 0.74-0.81, p < 0.05). Pathology-based RCB positively correlated with post-treatment DCE metrics (p = 0.76-0.70, p < 0.05) and negatively with ADC (p = -0.79, p = 0.03).Conclusion: Given the heterogeneity of PCa, an individualized approach to ADT may maximize potential benefit. This pilot study suggests that mpMRI may serve as a biomarker of ADT response and as a surrogate for RCB at prostatectomy.