68-Ga-psma-pet in Lymph Node Staging in PSA Recurrent Prostate Cancer-Does the Primary Influence the Result?

210 Background: Prostate cancer is the most common cancer in western countries. 68Ga PSMA-PET is the most accurate tool to detect lymph node metastases even at low PSA values. Salvage lymph node dissection prolongs biochemical recurrent free survival, whereas salvage radical prostatectomy has the potential to achieve long term tumor control at least in node negative disease. We compared the diagnostic value of 68Ga-PSMA PET in patients with biochemical recurrence after radical prostatectomy an salvage radiotherapy (Group1) and in patients with local recurrence after radiotherapy (Group2) to evaluate the influence of the primary. Methods: We retrospectively reviewed 57 and 31 patients in Group I and II respectively. In Group I a salvage lymph node dissection was performed on the side of the positive PSMA-staining. In Group II an extended pelvic lymph node dissection was performed in addiction to a salvage radical prostatectomy. Sensitivity, Specificity, posisive and negative predictive value as well as accuracy of PSMA-PET was calculated per lesion. Results: A total of 649 (2-32) and 515 (3-29) lymph nodes had been dissected. In 39 (68%) and 11(35,5%) at least one positive lymph node could be found. Mean diameter of the metastases was 0,81 (0,1-2,6)cm and 0,8(0,1-2) cm respectively. Sensitivity, Specificity, pos and neg. predicitve value as well as accuracy in Group I and two are 85, 96, 77, 98, 94,6 and 40, 100, 100, 98, 97,6%. Conclusions: In salvage surgeries in PCA good diagnostic tools to identify lymph node metastases are mandatory. With the primary in situ there is a significant reduced sensitivity of only 40% to identify positive nodes. The specific role of the primary tumor is not yet known.