Indications for Pelvic Lymphadenectomy

Introduction

The introduction of prostate-specific antigen (PSA) screening during the 1990s has decreased the incidence of prostate cancer lymph node metastasis in contemporary surgical series. This observed stage migration coupled with improvements in axial imaging has largely obviated the need for pelvic lymph node dissection (PLND) as an independent staging procedure. As a consequence, current practice patterns largely integrate PLND simultaneously with open or minimally invasive prostatectomy when clinically indicated. High-level scientific evidence in the form of randomized studies is lacking thereby predicating interpretation of the diagnostic and therapeutic benefit of LND from retrospective analyses. In this chapter, we discuss the indications, role of predictive models, significance of anatomic boundaries, and therapeutic yield associated with PLND for the management of prostate cancer.

Risk stratification for performing pelvic lymphadenectomy

PLND is an effective and reliable diagnostic modality for the staging of prostate cancer and discovery of metastatic disease. Predictive models have also demonstrated that lymph node yield is a significant predictor of detecting positive lymph nodes with a linear increase in probability with each node removed. Furthermore, some data implicate the potential for eradication of micrometastatic disease thereby contributing a therapeutic benefit realized via a survival advantage. Such observations, however, are largely predicated on the likelihood of detecting positive lymph nodes (LN) at PLND. In particular, Klein et al. explored the concept of number needed to treat (NNT) to cure one patient with biologically or histologically positive LN at PLND and suggested that (not surprisingly) the NNT rose progressively at lower likelihoods of positive nodes.

There are clearly some patients undergoing prostatectomy in whom PLND is unnecessary because of a low risk of nodal metastasis. With the increased use of PSA screening and the decreased macroscopic nodal burden at time of initial diagnosis, a trend toward less aggressive disease with significantly less nodal metastases has been clearly demonstrated at time of surgery. Such observations have contributed to population registries noting decreased utilization of PLND. Analysis of the CAPSURE database, for example, highlighted a trend to decreased PLND for low- and intermediate-risk patients undergoing prostatectomy. Specifically, for low- to intermediate-risk patients, while 94% underwent PLND in 1992, this percentage decreased to 80% in 2004.

A formal decision tree analysis has been used to evaluate the risk-to-benefit ratio of PLND at the time of prostatectomy. The analysis was based on two assumptions: (1) prostatectomy would be aborted if frozen section noted positive lymph nodes and (2) lymphadenectomy had no therapeutic benefit. With such considerations, the study suggested that lymph node dissection can be omitted in patients whose risk of lymph node involvement is less than 18%. Collectively, such observations highlight the need for refined risk stratification to appropriately select patients suitable for PLND prior to surgery.