Extended vs standard lymph node dissection in robot-assisted radical prostatectomy for intermediate- or high-risk prostate cancer: a propensity-score-matching analysis

Abstract

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Although lymph node dissection (LND) is known as the most accurate method of nodal staging, the therapeutic role of LND remains undetermined. This is mainly because of the lack of randomized prospective studies and the fact that retrospective analyses often result in bias and misinterpretation. To overcome the limitation of retrospective analysis, we matched preoperative variables using propensity scores and compared the outcomes between patients treated with robot-assisted eLND and sLND. In the matched cohort, robot-asssited eLND achieved an increased detection rate of lymph node metastases; however, the therapeutic benefit was not statistically significant between the two groups on short-term follow-up. OBJECTIVE: To compare the pathological and biochemical outcomes between extended lymph node dissection (eLND) and standard lymph node dissection (sLND) in patients undergoing robot-assisted radical prostatectomy for intermediate- or high-risk prostate cancer. PATIENTS AND METHODS: A total of 905 patients underwent robot-assisted radical prostatectomy and lymph node dissection (LND) by a single surgeon between June 2006 and January 2011. Of these, 170 patients who underwent robot-assisted eLND and 294 patients who underwent robot-assisted sLND for intermediate- or high-risk prostate cancer were included in the study. Propensity-score matching was performed using the preoperative variables which included age, body mass index, prostate-specific antigen, clinical stage, biopsy Gleason score 1 and 2, total number of biopsied cores, number of positive cores and prostate volumes. Pathological and biochemical outcomes were assessed according to the extent of LND. RESULTS: The median (range) follow-up period was 36 (12-77) months and the median number of lymph nodes removed was 21 and 12 in the eLND and sLND groups, respectively. Propensity-score matching resulted in 141 patients in each group. Although patients who underwent eLND had a higher clinical stage, biopsy Gleason score and number of positive cores than those treated with sLND in the entire cohort, there were no preoperative between-group differences in the matched cohort. In the matched cohort, lymph node metastases were detected at a significantly higher rate in the eLND than in the sLND group (12.1 vs. 5.0%, P = 0.033). In the matched cohort, the 3-year biochemical recurrence-free survival rates were 77.8 and 73.5% in the eLND and sLND groups, respectively, which was not significant (hazard ratio 0.85, P = 0.497). CONCLUSION: Robot-assisted eLND achieved an increased lymph node yield and higher detection rate of lymph node metastases; however, robotic eLND did not alter biochemical outcomes in a short-term follow-up.