Date Published: February 5, 2019
Publisher: Public Library of Science
Author(s): Mei-Wen Chen, Chien-Pin Chan, Yih-Jeng Lin, Hsu-Heng Yen, Ali Osmay Gure.
A hybrid topographic and numeric lymph node (LN) staging system for gastric cancer, which was recently proposed by Japanese experts as a simple method with a prognostic predictive power comparable to the N staging of the American Joint Committee on Cancer (AJCC) Tumor-node-metastasis classification, has not yet been validated in other Asian countries. This study aimed to examine the prognostic predictability of the hybrid staging system with the current AJCC staging system in gastric cancer.
Overall, 400 patients with gastric cancer who underwent surgery at Changhua Christian Hospital from January 2007 to December 2017 were included in the study. Univariate and multivariate analyses were performed to identify prognostic factors for gastric cancer-related death. Homogeneity and discrimination abilities of the two staging systems were compared using likelihood ratio chi-square test, linear trend chi-square test, Harrell’s c-index, and bootstrap analysis.
One-third of the LN-positive patients were reclassified into the new N and Stage system. The concordance rates of the two staging systems and the N staging between the two staging systems were 0.810 and 0.729, respectively. Harrell’s c-indices for the stage and N staging were higher in the 7th AJCC staging system than the hybrid staging system (c-index for stage, 0.771 vs 0.764; c-index for nodal stage, 0.713 vs 0.705). Stratification of the patients according to the histological grade revealed that Harrell’s c-indices for the stage and N stage of the hybrid staging system were comparable with those of the 7th AJCC staging system (c-index for AJCC stage vs hybrid stage, 0.800 vs 0.791; c-index for AJCC N stage vs hybrid N stage, 0.746 vs 0.734) among patients with histologically lower grade gastric cancer. The performance of the new nodal staging system was better than that of the 7th AJCC staging system by likelihood ratio and linear trend tests and bootstrap analysis in the low-grade group.
The hybrid anatomical location-based classification may have better prognostic predictive ability than the 7th AJCC staging system for LN metastasis of low-grade gastric cancer. Further studies involving different ethnic populations are necessary for the validation of the new staging system.
Gastric cancer incidence rates vary wildly between males and females and across different countries.[1, 2] The lifetime risk of gastric cancer is higher in Japan, Korea, and India; intermediate at approximately 3% in Eastern Europe, South America, and certain regions in Asia including parts of China and the Golestan Province in Iran; and low in other countries.[1, 2] The tumor-node-metastasis (TNM) classification and staging system of the American Joint Committee on Cancer (AJCC) is the most important reference for accurate and reproducible staging of gastric cancer in daily practice, and periodic and reasonable revisions of the TNM staging system are made by the Union for International Cancer Control and the AJCC.[3, 4] More than half of patients with gastric cancer have lymph node (LN) metastasis at diagnosis or after surgery, with poor prognosis. Before its 5th edition, nodal (N) staging within the TNM classification was based on the anatomical extent of LN metastasis. Starting with the 5th AJCC edition, N staging has been based on the number of involved LNs[7, 8] and the anatomic extent of LN metastasis is no longer included. Unlike tumor (T) staging within the TNM classification, which relies on pathological assessment, harvesting LNs for N staging relies on surgical techniques. The numeric N staging does not offer information on the anatomical extent of disease and does not represent the quality of LN dissection.[9, 10] For instance, D2 lymphadenectomy with dissection of perigastric and extraperigastric LNs, which is usually performed in the East and has been recently recommended in the West, provides more information on metastatic LNs compared with D1 resection. Using data from Japan and Korea, Choi et al. proposed a hybrid LN staging system, which demonstrated a prognostic performance equal to that of the 7th edition of the TNM system. This new and simple staging system was proposed to be a reliable alternative to the current numeric-based system in an Italian study.
In this retrospective study, we found that the hybrid anatomy-based staging system provided a better overall prognostic stratification than the 7th AJCC staging system in patients with lower histological grade gastric cancer. In contrast with the previous studies by Choi et al. and Gennaro et al., both of which suggested that the hybrid anatomy-based staging system was better than the currently utilized 7th AJCC staging system, our findings suggest that the tumor histological grade might play an important role and should be considered in this hybrid anatomy-based staging system to improve the homogeneity and the discriminatory ability of the current AJCC staging system.
Despite its simplicity, the current study results suggest that the hybrid anatomy-based staging system developed by Choi et al.(10) exhibited improved performance only for patients with histologically low-grade gastric cancer. Additional studies with larger sample sizes and different ethnic populations should compare the performance of the new anatomy-based LN stating system with the existing AJCC staging system.