Extension and rate of lymph node invasion of pelvic lymph node dissection during robot-assisted radical prostatectomy according to D'Amico classification. An analysis of a single-center experience

Aim of the study Pelvic lymph node dissection (PLND) is the most accurate staging procedure for patients diagnosed with organ-confined prostate cancer who undergo radical prostatectomy. Several studies showed that an extended PLND is feasible during robotic assisted radical prostatectomy (RARP). To evaluate extension of PLND and lymph nodes metastasis rates, according to D’Amico’s classification, in patient underwent to RARP and PLND in our Institution. Materials and methods Between January 2011 to March 2013, 286 patients underwent RARP in our Institution. Of these, 173 were evaluable for the analysis. We retrospectively reviewed our prospectively collected database and stratified patients into 3 groups according to D’Amico classification. Then we performed a comparison between standard (sPLND) versus extended PLND (ePLND). Results The preoperative characteristics of the patients are shown in table 1. According to d’Amico classification, 45 patients (26%) were classified as high risk, 60 patients (35%) as intermediate risk while the remaining 68 patients (39%) were low risk. Overall, PLND was performed in 72 patients (41.6%). Of these, 37 were high risk (51.4%), 34 intermediate risk (47.2%) and one patient was low risk (1.4%). In the high risk group, 37/45 patients (82.2%) underwent PLND, 34/60 (56.7%) in the intermediate group and 1/68 (1.5%) in the low risk group. The mean number of nodes removed was overall 17.25+/-11.1; 17.05+/- 7.7 in the high risk group, 17.27+/-14.1 in the intermediate risk group and 24 in the low risk group. Among patients who performed PLND, lymph node invasion (LNI) was found in 15 patients (20.8%). LNI was found in zero, 5 (14.5%), and 10 (27%) of the low, intermediate, and high risk patients who underwent PLND, respectively ( table 2) ePLND was performed in 22/72 patients (30.5%). The mean number of nodes removed was 14.06 +/-7.3 for the sPLND and 24.36 +/-14.6 for the ePLND. LNI was observed in the 16.3% of sPLND and in the 27.3% of ePLND. The lymph nodes density was 2.3% for sPLND and 2.0% for ePLND. Discussion In our cohort we observed a higher rate of LNI to those reported in literature, especially in high risk patients. As expected, ePLND is associated with high number of lymph nodes removed. The strengths of this study are the stratification into risk groups and the comparison between standard and extended PLND; all specimens were analysed by expert pathologists. Limitations of this study are its retrospective design and the limited number of patients included. Conclusions In our experience, the lymph node yeld in the robotic setting is satisfactory. The extended template of PLND improves staging and increases detection rate of LNI. D’Amico risk classification can be considered a good predictor of LNI in patients undergoing PLND during RARP.