178 A SINGLE SPOT AT [(11)C]CHOLINE-PET/CT SCAN IS NOT PREDICTIVE OF A SINGLE, ISOLATED NODAL METASTASIS AT FINAL PATHOLOGY. IMPLICATIONS FOR SALVAGE TREATMENTS

Abstract

INTRODUCTION AND OBJECTIVES: Several studies have reported good accuracy of integrated [(11)C]choline-PET/CT scan in the diagnosis of lymph node metastasis (LNM) in men with biochemical (BCR) and nodal recurrence after radical prostatectomy (RP). Salvage nodal dissection (sLND) as well as targeted radiotherapy (RT) might represent possible treatment options for this highly selected category. However, it is still unclear whether any salvage treatment should exclusively target those lymph nodes (LNs) with pathological uptake at PET/CT scan. The aim of our study was to assess the value of PET/CT scan in identifying the presence of a single LNM in a cohort of pts with BCR after RP. METHODS: The study included 47 patients with BCR (defined as a PSA 0.2 ng/ml) after RP and a single positive LN uptake at PET/CT. All patients underwent sLND including either pelvic alone (n 13) or pelvic retroperitoneal sLND (n 34). Clinical and pathological data, including PSA at recurrence, pathological stage, number of LNs removed, number and sites of positive LNs at final pathology was collected for all pts. Moreover, the correlation between imaging findings and presence and site of LNM according to anatomical location was evaluated. RESULTS: Mean number of LN removed at sLND was 25 (median 21; range 5-85), while mean number of positive LNs was 4.8 (median 2: range 0-37). Mean PSA at sLND was 1.16 ng/ml. Of 47 patients with a single LN uptake at PET/CT scan, 34 (72.3%) had LNM in the area indicated by PET/CT scan. Of these, 18 (38.3%) had a confirmed diagnosis of LNMs in the corresponding site that was indicated by PET/CT scan. However, only 9 out of 18 (50%) patients had confirmed single positive LN at final pathology, while the remaining 9 men (50%) had at least 2 positive LNs within the same anatomical region.Interestingly, in 16 patients (34%) positive LNs were also found either contra-laterally in the pelvis or in the retro-peritoneum in addition to the confirmed LNMs suggested at PET/CT. Finally, 4 men (8.5%) had no correspondence between the site of positive PET/CT and the site of positive LNs at sLND, while the remaining 9 patients (19%) had no positive LNs at final pathology. CONCLUSIONS: This is the first study assessing the pathological outcome of men with a single positive spot at PET/CT scan. We demonstrated that in patients with a single positive spot at PET/CT scan, the probability of having a single corresponding pathological LN is low (19%). This should be taken into account when targeting salvage therapies are considered as treatment options for men with isolated LN recurrence.