Prognostic impact of microscopic vessel invasion and visceral pleural invasion in non-small cell lung cancer: a retrospective analysis of 2657 patients.

OBJECTIVE: We aimed to assess the prognostic significance of microscopic vessel invasion (MVI) and visceral pleural invasion (VPI) in non-small cell lung cancer (NSCLC).

BACKGROUND: VPI is included in the current tumor-node-metastasis (TNM) classification in NSCLC; however, MVI is not incorporated in TNM classification.

METHODS: From August 1992 to December 2009, 2657 consecutive patients with pathological T1-4N0-2M0 NSCLC underwent complete resection. In addition to conventional staging factors, we evaluated MVI histologically and analyzed its significance in NSCLC recurrence prognosis. The recurrence-free period in several NSCLC subgroups was analyzed using the Kaplan-Meier method and Cox regression analysis.

RESULTS: The proportion of patients with a 5-year recurrence-free period was 52.6% and 87.5%, respectively, in those with and without MVI (P < 0.001). Multivariate analysis showed that MVI, similarly to VPI, was found to be an independently significant predictor of recurrence [hazard ratio (HR): 2.78]. In particular, MVI and VPI were the 2 strongest significant independent predictors of recurrence in 1601 patients with pathological stage I disease treated without adjuvant chemotherapy (HR: 2.74 and 1.84, respectively). In each T subgroup analysis, evident and significant separation of the recurrence-free proportion curves were observed among the 3 groups (VPI and MVI absent, VPI or MVI present, and VPI and MVI present).

CONCLUSIONS: This study demonstrated that MVI was a significant independent risk factor for recurrence in patients with a resected T1-4N0-2M0 NSCLC. Further data on MVI prognostic impact should be collected for the next revision of the TNM staging system.