Pathologic nodal staging scores in patients treated with radical prostatectomy: a postoperative decision tool.

Background: Nodal metastasis is the strongest risk factor of disease recurrence in patients with localized prostate cancer (PCa) treated with radical prostatectomy (RP).

Objective: To develop a model that allows quantification of the likelihood that a pathologically node-negative patient is indeed free of nodal metastasis.

Design, Setting, And Participants: Data from patients treated with RP and pelvic lymph node dissection (PLND; n=7135) for PCa between 2000 and 2011 were analyzed. For external validation, we used data from patients (n=4209) who underwent an anatomically defined extended PLND.

Intervention: RP and PLND.

Outcome Measurements And Statistical Analysis: We developed a novel pathologic (postoperative) nodal staging score (pNSS) that represents the probability that a patient is correctly staged as node negative based on the number of examined nodes and the patient's characteristics.

Results And Limitations: In the development and validation cohorts, the probability of missing a positive node decreases with an increasing number of nodes examined. Whereas in pT2 patients, a 90% pNSS was achieved with one single examined node in both the development and validation cohort, a similar level of nodal staging accuracy was achieved in pT3a patients by examining five and nine nodes, respectively. The pT3b/T4 patients achieved a pNSS of 80% and 70% when 17 and 20 nodes in the development and validation cohort were examined, respectively. This study is limited by its retrospective design and multicenter nature. The number of nodes removed was not directly correlated with the extent/template of PLND.

Conclusions: Every patient needs PLND for accurate nodal staging. However, a one-size-fits-all approach is too inaccurate. We developed a tool that indicates a node-negative patient is indeed free of lymph node metastasis by evaluating the number of examined nodes, pT stage, RP Gleason score, surgical margins, and prostate-specific antigen. This tool may help in postoperative decision making.