Prognostic impact of N1 lymph node micrometastasis in T1-2a Non-small cell Lung Cancer.

OBJECTIVES

Lymph node micrometastasis, defined as tumor deposits <2 mm, has been proposed as an adverse prognostic factor in early-stage non-small cell lung cancer (NSCLC), but its clinical significance remains unclear. This study aimed to evaluate the prognostic impact of N1 micrometastasis in patients with T1-2a NSCLC.

PATIENTS AND

METHODS

We retrospectively analyzed patients with pathologically confirmed T1-2a NSCLC who underwent complete resection-including lobectomy or more extensive procedures-with systematic lymph node dissection between 2000 and 2015. N1 micrometastasis was identified by cytokeratin immunohistochemistry and quantified using digital slide analysis.

RESULTS

Among 617 patients, 550 had no lymph node metastasis, 22 had N1 micrometastasis, and 45 had N1 macrometastasis. In univariate analysis, patients with N1 micrometastasis had significantly worse recurrence-free survival (RFS) and overall survival (OS) compared with those without lymph node involvement (5-year RFS: 53.3 % vs. 85.1 %, P < 0.001; 5-year OS: 61.5 % vs. 87.0 %, P = 0.007). Multivariate analysis identified N1 micrometastasis as an independent adverse prognostic factor for RFS (HR 2.589, 95 % CI 1.388-4.829, P = 0.003) and OS (HR 2.179, 95 % CI 1.052-4.513, P = 0.036). Furthermore, stabilized inverse probability of treatment weighting (IPTW)-adjusted analysis confirmed significantly worse RFS (HR 2.992, 95 % CI 1.276-7.018, P = 0.012), whereas the difference in OS did not reach statistical significance (HR 2.207, 95 % CI 0.855-5.698, P = 0.102).

CONCLUSIONS

N1 lymph node micrometastasis is a significant negative prognostic factor for RFS in T1-2a NSCLC. These findings support further prospective studies to validate its role in guiding treatment decisions for early-stage NSCLC.

SHORT ABSTRACT: We retrospectively analyzed patients with pathologically confirmed T1-2a non-small cell lung cancer (NSCLC) who underwent complete resection with systematic lymph node dissection. Multivariate and stabilized inverse probability of treatment weighting (IPTW)-adjusted analyses identified N1 lymph node micrometastasis as a significant adverse prognostic factor for postoperative recurrence-free survival (RFS).