Prognostic roles of lymph node micrometastasis in non-small cell lung cancer.

Objective: This study aimed to confirm the prognostic roles of lymph node (LN) micrometastasis (LNMM) in non-small cell lung cancer (NSCLC) through a meta-analysis.

Methods: This study included 2026 NSCLC cases without detection of LN metastasis in histologic examination. We investigated the detection rate of LNMM in early-stage NSCLC and analyzed the correlation between LNMM and the rates of recurrence and survival.

Results: The range of detection rates of LNMM was 3.8-68.8% in the eligible studies. The detection rate of LNMM in early-stage NSCLC was 25.3% (95% confidence interval [CI] 19.8-31.6%). In subgroup analysis based on detection method, polymerase chain reaction method had higher detection rate than immunohistochemistry (33.7%, 95% CI 25.5-43.0% vs. 23.1%, 95% CI 18.0-29.0%). The presence of LNMM was significantly correlated with a higher recurrence rate (odds ratio 3.913, 95% CI 1.595-9.600, P=0.003). In addition, there were significant correlations between LNMM and worse overall and disease-free survival rates (hazard ratio [HR] 2.345, 95% CI 1.863-2.951, and HR 1.606, 95% CI 1.170-2.206, respectively).

Conclusion: Taken together, our results showed that LNMM was detected in 25.3% of NSCLCs without nodal disease through ancillary test. In addition, the presence of LNMM was significantly correlated with a higher recurrence rate and worse survival rates in early-stage NSCLC.