242 11C-ACETATE PET/CT IMAGING OF PROSTATE CANCER LYMPH NODE METASTASES AND CORRELATION WITH LYMPHADENECTOMY AND HISTOPATHOLOGY FINDINGS

INTRODUCTION AND OBJECTIVES: The choice of treatment in patients with prostate cancer (PCa) is often determined by the existence of tumor spread to regional lymph nodes. In this study, we evaluated the accuracy of PET/CT with 11C-acetate to detect regional lymph node metastases with strict correlation to surgical defined locations and histopathological results. METHODS: A total of 19 PCa patients staged with 11C-acetate-PET/CT imaging were included. All cases underwent extended pelvic lymph node dissection (ePLND) with lymph node sampling according to side and localisation. Group A: 10 patients with biochemical recurrence after RP and positive lymph nodes on 11C-acetate PET/CT Imaging underwent ePLND. Group B: 8 patients had an ePLND at RP and 1 subject an ePLND before curative radiotherapy. Median pre-operative PSA was for Group A (n 10): 0.83 ng/ml (range: 0.1-1.6) and Group B (n 9): 26.2 ng/ml (range: 6.1-130). We collected an average of 6.2 PLND sites per patient (range: 4 8).The tissue samples from each PLND site were sent for histopathological examination in separate test-tubes and analysed separately. Accordingly we had a total of 118 sites for histopathological analyses to compare with the PET/CT images. A postoperative PET/CT was scheduled 3 months after surgery in all patients. RESULTS: For each patient a mean of 25 (range 8-50) lymph nodes were obtained at surgery. Ten patients were positive for lymph node metastases on histopathology. A total of 484 lymph-nodes were examined by the pathologists and 44 of these were positive for malignancy. Good correlation between 11C-acetate-PET/CT report and histopathology was seen in 15 cases resulting in 90% sensitivity and 67% specificity. Postoperative control 11C-acetate-PET/CT imaging was suspicious for progression in 4 patients. CONCLUSIONS: 11C-acetate PET/CT imaging in this limited material had a high sensitivity but lower specificity. Further clinical research on the use of 11C-acetate-PET/CT with optimizing scanning time and equipment may allow further improvement.