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PD40-05 LYMPH NODE YIELD AND METASTATIC PATTERN AFTER EXTENDED PELVIC LYMPH NODE DISSECTION IN ROBOTIC-ASSISTED LAPAROSCOPIC PROSTATECTOMY: 14 YEARS OF EXPERIENCE

INTRODUCTION AND OBJECTIVES: Limited data is available regarding the feasibility of robotic-assisted laparoscopic extended pelvic lymph node dissection (RALePLND) for prostate cancer (PC) and the lymph node (LN) yield for each anatomical zone. We aimed to determine the LN yield, distribution patterns and frequency of pelvic LN metastases after RALePLND in men with PC. METHODS: A retrospective analysis of a consecutive series of men who underwent robotic-assisted laparoscopic radical prostatectomy (RALRP) at our institution between 2004 and 2018 was conducted. RALePLND included the lymphatic tissue along the external iliac artery (medial) and vein, obturator nerve, in the obturator fossa and along the internal iliac artery. The LN yield in total and stratified for each anatomical zone, the frequency and pattern of LN metastases and complications were reported. RESULTS: Among 1,134 men undergoing RALRP, 27 patients with neoadjuvant hormonal treatment or conversion to open surgery were excluded. Of the remaining 1107 patients, 823 received a RALePLND (74.3%) and were analysed. The median number of LNs removed was 19 (range: 1 - 63); 10 on the right (range: 1 - 33) and 9 on the left side (range: 1 - 37). An average of 5.3 (± 1.8) LNs were removed from the internal, 6.1 (± 2.4) from the external iliac artery and 9.4 (± 2.5) from the obturator fossa. A total of 98 patients (11.9%) had LN metastases. Among them, 46 (46.9%) had one, 19 (19.4%) had two and 33 (33.7%) had more than two positive LNs. Stratified for anatomical zones, 64 (65.3%) had metastases along the external, 51 (52.0%) along the internal iliac artery and 58 (59.2%) in the obturator fossa. Forty-two men (42.9%) had metastases in more than one region. More men had nodal metastases on the right (n = 40, 40.8%) than on the left side (n = 20, 20.4%). This difference was also detected counting positive LNs (160 right vs. 97 left). Bilateral metastases were detected in 38 men (38.8%). If the internal iliacal nodes would not have been resected, 15 patients (15.3%) would have been understaged as pN0 and a total of 82 positive LNs (30.6%) would have been left in situ. The rate of clinically significant lymphoceles was low but higher than in patients not undergoing RALePLND (1.7% vs. 0.7%). CONCLUSIONS: RALePLND with a high LN yield is feasible and leads to a low rate of clinically significant lymphoceles. The inclusion of the internal iliac zones leads to detection and resection of a significant number of positive LNs. Source of Funding: None.