Metastatic Prostate Adenocarcinoma with Urinary Bladder involvement by two different routes (direct extension and hematogenous seeding): Dual tracer PET (68Ga-PSMA-11 and FDG) and CT Imaging features and their role in assessing and predicting response to 177Lu-PSMA-617 Radioligand Therapy vis-à-vis conventional risk categories

The present communication details on the imaging characteristics, peculiarities and response to PSMA targeted (177)Lu-PSMA-617 PRLT in accordance with Gleason score and use of dual tracer PET study ((68)Ga-PSMA-11 and FDG) in patients with urinary bladder invasion/metastasis by prostate cancer, including the prognostic value of FDG-PET in predicting response to treatment. The CT attenuation units (HU) correlated with prostate primary in case of direct tumour extension from prostate, while in hematogenous metastatic seeding the HU was lower than the primary prostatic tumour. A particular point of note was that favorable outcome to (177)Lu-PSMA-617 PRLT was observed in patients with lesser or no baseline FDG uptake despite high Gleason score and high risk NCCN prognostic category, and did not correlate with the latter alone, while high SUVmax values on FDG PET-CT was found to be associated with adverse outcome. These findings suggested the promising role of FDG PET-CT in predicting therapeutic outcomes with more confidence, and hence the concept of dual tracer PET appeared to hold good in prostate adenocarcinoma theranostics.