Prognosis for gastric carcinomas with an insufficient number of examined negative lymph nodes

Abstract

The optimal system for lymph node (LN) staging in gastric cancer is still a subject of debate. The aim of our study was to analyse the probability of error in negative LN (pN0) gastric carcinomas when a low number of LNs were harvested using a probabilistic model. Patients with gastric carcinoma who underwent R0 resection at three university hospitals between 2004 and 2009 were retrospectively included. A Bayesian model was used to analyse the probability of error for negative LNs (pN0) gastric carcinomas. Kaplan-Meier survival curves and the log-rank test were used to compare the overall and specific mortality of prognosis groups. Of the 291 patients included, 123 were classified as pN0 (42%). A significant correlation was found between the extent of the LN dissection performed and the number of the LNs retrieved. According to the Bayesian model the carcinomas with 9 or fewer negative lymph nodes were considered to have a high risk (HR) of misclassification, whereas patients with 10-25 LNs analysed and those with more than 26 negative lymph nodes were considered to have a moderate risk (MR) and low risk (LR), respectively. The log-rank test showed a significant improvement in the disease-specific survival for the MR pN0 (p<0.001) and LR pN0 (p<0.04) but not for the HR pN0 patients compared to pN1 patients. The proposed probabilistic model is clinically useful for differentiating the prognosis in pN0 gastric carcinomas when an insufficient number of negative lymph nodes are retrieved.