Lymph node micrometastases is a poor prognostic factor for patients in pN0 gastric cancer: a meta-analysis of observational studies

Abstract Background There is no consensus as to the impact of lymph node micrometastases (LNMM) on survival of patients with gastric cancer. The aim of this analysis was to investigate the prognostic significance of LNMM in patients with histologic node-negative gastric cancer. Methods We searched relevant studies from PubMed, Embase, and the Cochrane Library (1966–2013.5), used software STATA 12.0 to pool the outcomes of each study. Mantel-Haenszel and Inverse Variance methods were used in a fixed effect model and a random effect model, respectively. The hazard ratios (HR) and odds risk (OR) at their 95% confidence intervals (CIs) were used as measures to investigate the prognostic importance of LNMM, by searching for a correlation between the clinical pathologic features and LNMM. Results Our analysis of 18 eligible studies revealed that patients with LNMM had an increased likelihood of having a worse 5-y survival rate (HR 2.81; 95% CI：1.96–4.02). Subgroup analyses showed a more significant result for patients in pT1-2N0 (HR 3.52; 95% CI 1.88–6.62). The analyses also revealed that (OR 1.32; 95% CI 1.17–1.48), lymphatic invasion (OR 2.21; 95% CI 1.42–3.44) and venous invasion (OR 1.41; 95% CI 1.08–1.85) were associated with the occurrence of LNMM. Conclusions There is a positive correlation between LNMM and an unfavorable surgical outcome in gastric cancer. Undifferentiated histologic findings, lymphatic invasion, and venous invasion are high risk factors for the occurrence of LNMM.