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

2. 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.

3. 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.

4. Prostate Adenocarcinoma Details Baseline Characteristics Variable N% Clinical T-stage T1834.8 T2730.4 T3521.7 T428.7 NA14.3 Biopsy Gleason Score ≤614.3 7.0417.4 8-101773.9 NA14.3 Pre-treatment PSA (ng/mL) Median11.7 Range1.1-100.0 Metastases at diagnosis11.047.8 Treatment of adenocarcinoma Radiotherapy730.4 Prostatectomy626.1 Primary ADT1043.5 Radiotherapy details* EBRT alone521.7 EBRT + brachytherapy28.7 NeoADT521.7 Surgery details (n=6) pathologic t-stageT3626.1 pathologic n-stageN028.7 N1417.4 Salvage EBRT28.7

5. Variable N% Method of initial diagnosis Biopsy28.7 Elevated CrA2191.3 Initial CrA level Median110.0 Mean130.5 Range30.0-442.0 Highest CrA level Median142.0 Mean170.9 Range88.0-444.0 Number of FDG-PET scans after NEPC diagnosis Median2 Range1-9 Extent of disease 0-5 sites626.1 6-25 sites834.8 26-50 sites626.1 50-110 sites313.0 Neuroendocrine Prostate Cancer Details Characteristics

6. 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.

7. Table 2. Skeletal lesion analysis per patient

8. Table 3. Soft tissue lesion analysis per patient

9. 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).

10. J591FDG Bone Scan

11. FDHT FDGBone Scan

12. 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