Comparison of Dual-Tracer PET and CT Features to Conventional Risk Categories in Assessing Response to ¹⁷⁷Lu-PSMA-617 Therapy for Metastatic Prostate Adenocarcinoma with Urinary Bladder Involvement

Abstract

The present communication details the imaging characteristics, peculiarities, and response to ¹⁷⁷Lu-labeled prostate-specific membrane antigen (PSMA)-617–targeted radioligand therapy (PRLT) in accordance with Gleason score and use of dual-tracer PET (⁶⁸Ga-PSMA-11 and ¹⁸F-FDG) in patients with urinary bladder invasion or metastasis by prostate cancer, including the prognostic value of ¹⁸F-FDG PET in predicting response to treatment. The CT attenuation units (Hounsfield units) correlated with the prostate primary in the case of direct tumor extension from the prostate, whereas in hematogenous metastatic seeding the Hounsfield units were lower than in the primary prostatic tumor. A favorable outcome to ¹⁷⁷Lu-PSMA-617 PRLT was observed in patients with low or no baseline ¹⁸F-FDG uptake despite a high Gleason score and a high-risk National Comprehensive Cancer Network prognostic category and did not correlate with the latter alone, whereas a high SUV_max on ¹⁸F-FDG PET/CT was associated with an adverse outcome. These findings suggest a promising role for ¹⁸F-FDG PET/CT in predicting therapeutic outcomes more confidently, and hence the concept of dual-tracer PET appears to hold good in prostate adenocarcinoma theranostics.