Value of Whole-body Magnetic Resonance Imaging Using the MET-RADS-P Criteria for Assessing the Response to Intensified Androgen Deprivation Therapy in Metastatic Hormone-naïve and Castration-resistant Prostate Cancer.

Background and objectives: We assessed the agreement between prostate-specific antigen (PSA) and imaging responses using whole-body magnetic resonance imaging (wbMRI). Our aim was to explore the potential prognostic value of PSA and wbMRI responses in metastatic hormone-naïve prostate cancer (mHNPC) and castration-resistant PC (mCRPC).

Methods: wbMRI was prospectively performed in 37 patients with mHNPC and 51 with mCRPC before and after 6-12 mo of androgen deprivation therapy and an androgen receptor pathway inhibitor (ARPI). Imaging responses were defined according to the Metastasis Reporting and Data System for PC (MET-RADS-P) criteria. A PSA response was defined as PSA ≤0.2 ng/ml in mHNPC and a ≥50% decrease from the pretreatment level in mCRPC. Agreement between PSA and wbMRI responses was assessed using Cohen's κ. The association between time to subsequent treatment and overall survival (OS) was analyzed using Cox regression analysis.

Key findings and limitations: Agreement between PSA and wbMRI responses was fair in mHNPC (κ = 0.30) but none to slight in mCRPC (κ = 0.15). In mHNPC, patients with a PSA or wbMRI response were less likely to receive subsequent treatments; wbMRI progression was associated with a significantly higher risk of death (hazard ratio 8.59; p = 0.002). In mCRPC, two-thirds of patients with a PSA response showed progression on wbMRI; neither PSA nor wbMRI progression changed the likelihood of starting a subsequent treatment or the risk of death.

Conclusions and clinical implications: In mHNPC, wbMRI progression was associated with a higher risk of needing subsequent treatment and shorter OS.

Patient summary: We evaluated the agreement between routine PSA (prostate-specific antigen) test results and whole-body MRI (magnetic resonance imaging) scans for assessing the response of metastatic prostate cancer to treatment. There was disagreement between the PSA and MRI results, mainly for patients with cancer that was resistant to hormone-based treatment. Combining PSA with whole-body MRI might provide a more accurate picture of the response of advanced prostate cancer to treatment.