Differences between whole body magnetic resonance imaging (WB-MRI) and chest/abdomen/pelvis computed tomography (CT)/bone scan (CT/B) in patients staged as having metastatic hormone-sensitive prostate cancer (mHSPC): A retrospective comparative study within a single trust in the UK.

Abstract

37 Background: Diagnostic imaging for metastases detection in HSPC varies across different countries with increasing use of WB-MRI and PSMA-PET. However, CT/B has still been the most used modality in the real world and recent registration clinical trials in this disease setting. Methods: We performed a cross-sectional retrospective descriptive study comparing WB-MRI with CT/B used as baseline staging modalities in patients diagnosed with mHSPC between February 2017 and August 2023 in two hospitals belonging to the same NHS trust in the UK routinely using one of the two. The study aimed at the detection of differences between the two modalities in the identification of metastatic sites and CHAARTED volume/LATITUDE risk, and the relative impact on patients’ received therapies and outcomes. Results: Of 213 patients diagnosed with mHSPC, 121 had baseline WB-MRI, 86 CT/B and 7 choline or PSMA PET. Compared to CT/B, patients staged by WB-MRI were diagnosed with significantly higher bone-only (47 vs 24%, p=0.002) and lower lymph-node only disease (11 vs 27%, p=0.005); higher high-volume (49 vs 21%, p<0.001) and -risk disease (48 vs 17%, p<0.001); higher de-novo metastatic disease (91 vs 66%, p<0.001); had previously received less radical surgery (2 vs 13%, p=0.003) or radiotherapy (7 vs 24%, p<0.001); received more frequently ADT plus Docetaxel (65 vs 44%, p=0.005). Treatment and outcome results in the overall cohorts’ populations and according to disease volume/risk will be presented. Conclusions: In a homogenous cohort of patients, we found a relevant discrepancy between the use of WB-MRI and CT/B in the identification of high-volume/risk and de-novo disease in mHSPC related to a higher detection rate of bone-only disease by the WB-MRI. This may prompt clinicians to offer different systemic therapies according to the disease burden and could also have a role in avoiding overtreatments for the under-staged disease.