The significance of microvascular invasion after complete resection of early-stage non-small-cell lung cancer

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was 'in patients with non-small-cell lung cancer who have undergone complete resection, does the presence of microvascular invasion (MVI) significantly impact long-term survival or prognosis?' Altogether, more than 250 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. Outcome parameters that were used in the assessment include 5-year overall survival, event-free or recurrence-free survival (RFS) and incidence of metastatic relapse. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. The majority of the data collected were retrospective. Meta-analysis of data of over 16 000 patients showed that when considering RFS, MVI positivity was associated with a significantly reduced period of RFS; pooled hazard ratio estimates by univariate and multivariate analyses were 3.28 (95% CI 2.14-5.05; P < 0.0001) and 3.98 (95% CI 2.24-7.06; P < 0.0001), respectively. Eight of the studies showed a significantly worse 5-year survival in the presence of MVI, whereas a further study found a reduced median survival with MVI. One study showed no difference, but concurred with five other studies that MVI was associated with a significantly shorter event-free or RFS. Multivariate analyses have furthermore demonstrated that MVI positivity correlates with larger tumour size, an increased risk of distant metastases, visceral pleural involvement, lymphovascular invasion, higher tumour grade and nodal status. We conclude that the presence of microvascular invasion in resected early-stage non-small-cell lung cancer is a negative prognostic factor.