Tumor Size Improves the Accuracy of the Prognostic Prediction of Lymph Node–Negative Gastric Cancer

Abstract

Background

Tumor size has been regarded as the “T” stage of many solid tumors because of its effect on prognosis. However, the prognostic impact of tumor size in gastric cancer (GC) is still controversial.

Materials and methods

A total of 436 patients with curatively resected GC and those without lymph node metastasis in our center were retrospectively enrolled. The appropriate cutoff points for tumor size were determined. Potential prognostic factors were analyzed. In addition, a pathological tumor-size (pTS) classification system was proposed to evaluate the superiority of its prognostic prediction of node-negative GC patients compared with that of the pT staging system.

Results

The ideal cutoff points for tumor size were 4 and 8 cm. In the multivariate analysis, tumor size was identified as an independent prognostic factor for node-negative GC patients after surgery, as was pT stage. The pTS classification was found to be more appropriate for predicting the overall survival of node-negative GC patients after curative surgery than pT stage, and the −2 log-likelihood of the pTS classification (1680.782) was smaller than the value of pT (1695.239).

Conclusions

As an independent prognostic factor, tumor size should be incorporated into the pT staging system to enhance the accuracy of the prognostic prediction of node-negative GC patients.

Introduction

Tumor size, given as the maximum diameter of the tumor, has been verified to be associated with overall survival (OS) in many types of malignancies.1, 2, 3, 4, 5, 6, 7, 8, 9 Tumor size is regarded as the “T” stage of many solid tumors, including breast, lung, and liver cancers, in the tumor-node-metastasis (TNM) staging system of the Union for International Cancer Control (UICC).1, 2, 3, 4, 5 Recently, many studies revealed that tumor size was correlated with the depth of invasion and lymph node metastasis and that it was an independent prognostic factor in gastric cancer (GC) patients as well.10, 11, 12, 13, 14, 15, 16, 17, 18 Despite the value of tumor size as a prognostic indicator in these studies, tumor size has not been incorporated into the TNM staging system for gastrointestinal tumors. The prognostic significance of tumor size is still uncertain.

Lymph node metastasis is an important prognostic factor for GC. GC patients with positive lymph nodes usually have poorer survival than those with node-negative disease, and it is vitally important to find better treatment tools and informative prognostic markers for these patients. However, the prognosis of node-negative GC is still unsatisfactory. Even after curative resection, some patients still develop early recurrence and metastasis.19, 20 Therefore, it is vitally important to identify possible prognostic factors of node-negative disease as well. In this study, we retrospectively analyzed the outcomes of 436 node-negative GC patients. The aim of this study was to evaluate the potential impact of tumor size on the long-term outcomes of GC patients after curative surgery and to test the clinical superiority of pathological tumor-size (pTS) classifications for the prognostic prediction in GC compared with pT stages of the eighth edition TNM staging system for GC.