Dan Spratt, MD Department of Radiation Oncology Neuroendocrine Prostate Cancer: FDG-PET and Targeted Molecular Imaging

Purpose Fluorodeoxyglucose (FDG) positron emission tomography (PET) has well-characterized limitations in prostate adenocarcinoma (PCA). However, data assessing the utility of PET in NEPC is limited to isolated case reports. Herein, we describe the first case series to assess the utility of FDG-PET in NEPC.

Material and Methods Inclusion criteria: – Clinically progressive metastatic PCa on ADT – Chromogranin-A levels >1.5x the upper limit of normal – ≥1 FDG-PET scan after the diagnosis of NEPC Yielded 23 patients. – All metastatic lesions on CT, PET, and bone scan were read by two independent physicians.

Prostate Adenocarcinoma Details Baseline Characteristics Variable N% Clinical T-stage T T T T428.7 NA14.3 Biopsy Gleason Score ≤ NA14.3 Pre-treatment PSA (ng/mL) Median11.7 Range Metastases at diagnosis Treatment of adenocarcinoma Radiotherapy730.4 Prostatectomy626.1 Primary ADT Radiotherapy details* EBRT alone521.7 EBRT + brachytherapy28.7 NeoADT521.7 Surgery details (n=6) pathologic t-stageT pathologic n-stageN028.7 N Salvage EBRT28.7

Variable N% Method of initial diagnosis Biopsy28.7 Elevated CrA Initial CrA level Median110.0 Mean130.5 Range Highest CrA level Median142.0 Mean170.9 Range Number of FDG-PET scans after NEPC diagnosis Median2 Range1-9 Extent of disease 0-5 sites sites sites sites313.0 Neuroendocrine Prostate Cancer Details Characteristics

Results Results: – 592 unique lesions were identified across all imaging modalities 510 were bone metastases 82 were soft tissue metastases. – Of bone lesions, 22.2%, 92.7%, and 77.6% were detected by PET, CT, and bone scan, respectively. – Of soft tissue lesions, 95.1% and 97.5% were detected by PET and CT, respectively.

Table 2. Skeletal lesion analysis per patient

Table 3. Soft tissue lesion analysis per patient

Results Results: – Stratified by the median survival from NEPC diagnosis (2.2 years): Patients who survived <2.2 vs. ≥2.2 years had more PET avid bone (8 vs. 2) and soft tissue lesions (7 vs. 1, p=0.01) Also had higher average SUVmax of bone (5.49 vs. 3.40, p=0.04) and soft tissue lesions (8.02 vs. 3.90, p=0.0002).

J591FDG Bone Scan

FDHT FDGBone Scan

In patients with clinical NEPC, we demonstrate that FDG-PET has clinical utility in the detection of metastatic disease, primary soft tissue disease. 89Zr-J591 and 18F-DHT may have clinical utility in characterizing NEPC vs adenoCa With novel therapies on the horizon to treat NEPC, consideration to investigate the use of FDG-PET to monitor response is warranted. Conclusions