Predictive factors for lymph node positivity in patients undergoing extended pelvic lymphadenectomy during robot assisted radical prostatectomy

Abstract

Introduction: Pelvic lymphadenectomy during radical prostatectomy (RP) improves staging and may provide a therapeutic benefit. However, there is no clear consensus on the selection criteria for subjecting patients to this additional procedure. With a growing adoption of robot assisted radical prostatectomy (RARP) in India, it has become imperative to study the incidence and predictive factors for lymph node involvement in our patients.

Materials and methods: From February 2010 to February 2014, 452 RARP procedures were performed at our institution. A total of 100 consecutive patients from July 2011 to August 2012 were additionally subjected to a robotic extended pelvic lymphadenectomy (EPLND). Lymph node positivity rates and lymph node density were analyzed on the basis of preoperative prostate specific antigen (PSA), Gleason score, clinical stage, D'Amico risk category and magnetic resonance imaging (MRI) findings. Multivariate analysis was performed to ascertain factors associated with lymph node positivity in our cohort.

Results: The mean age of the patients was 65.5 (47-77) years and the body mass index was 26.3 (16.3-38.7) kg/m(2). The mean console time for EPLND was 45 (32-68) min. A median of 17 (two to 40) lymph nodes were retrieved. Seventeen patients (17%) had positive lymph nodes (median of 1, range 1-6). Median lymph node density in these patients was 10%. When stratified by PSA, Gleason score, clinical stage, D'Amico risk category and features of locally advanced disease on MRI, a trend towards increasing incidence of lymph node positivity was observed, with an increase in adverse factors. However, on multivariate analysis, clinical stage > T2a was the only significant factor impacting lymph node positivity in our cohort.

Conclusions: A significant proportion of men undergoing RARP in India have positive lymph nodes on EPLND. While other variables may also have a potential impact, a higher clinical stage predisposes to an increased incidence of lymph node metastases.

Keywords: Extended pelvic lymphadenectomy; pelvic lymphadenectomy; prostate cancer; radical prostatectomy; robot assisted radical prostatectomy.

Figure 1

Extended pelvic lymphadenectomy template (right side) including the external iliac (zone 1), obturator (zone 2) and hypogastric (internal iliac) (zone 3) group of lymph nodes. CIA: Common iliac artery, EIV: External iliac vein, EIA: External iliac artery, IIA: Internal iliac artery, ON: Obturator nerve, OA: Obturator artery

Figure 2

Intraoperative picture of robotic extended pelvic lymphadenectomy (right side) showing important anatomical landmarks and zones of dissection

Figure 3

Receiver operating characteristics curve analysis of lymph node positivity in relation to clinical stage