How to evaluate the adequacy of staging for nodal-negative epithelial ovarian cancer? Use of nodal staging score.

Objective: No guideline has been provided to assess the minimal number of lymph nodes (LNs) that should be dissected for accurate staging in patients with epithelial ovarian cancer (EOC). The aim of the study was to develop a nodal staging score (NSS) as an index to assess whether a pathologic (p)N0 EOC patient is indeed free of a nodal disease.

Methods: A total of 16,361 EOC patients staged I-III between 2004 and 2013 were identified from the Surveillance, Epidemiology and End Result database. With a β-binomial model, NSS was calculated to assess the probability of true-negative findings of LN status.

Results: With an increased number of LNs examined, the probability of missing a nodal disease decreased and varied among different pT stages. Given 1 LN examined, an NSS of 93.76% calculated could ensure a high adequacy of nodal-negative classification for pT1N0 EOC patients. For pT2N0 patients, 5 LNs examined could guarantee an NSS of 90% for adequate staging. Likewise, 11 and 29 LNs examined in pT3N0 patients could maintain NSS at the level of 80% and 90%, respectively. Our study suggested the optimal number of LNs that could be examined and stratified by the pT stages for EOC patients based on this statistical model derived from large pathologic data of clinical surgery patients.

Conclusion: NSS, as an auxiliary tool, not only could assist the International Federation of Gynecology and Obstetrics staging more precisely, but also would provide a statistical basis for postoperative evaluation for further clinical decision-making.