Microvascular invasion as a prognostic indicator in renal cell carcinoma: a systematic review and meta-analysis

Microvascular invasion (MVI), an omen of potential hematogenous spread of tumor cells, has been identified as an accepted risk factor for poor prognosis in some solid tumors. But its prognostic value in renal cell carcinoma (RCC) remains disputable. In order to address this question rigorously, we performed a systematical review of the published literature on MVI and RCC prognosis. According to the PRISMA statement, we searched PubMed, Web of science, and Cochrane Library database and identified 33 cohort articles that met the eligibility criteria and involved 14,946 patients (48-2596 per study) in this meta-analysis. Using the random effects model, the association between MVI and four generally recognized end points were estimated, including cancer-specific survival (CSS), recurrence-free survival (RFS), metastasis-free survival (MFS) and overall survival (OS). The presence of MVI was detected in 14.4% of the pathological specimens. A higher incidence of MVI was associated with some acknowledged prognostic risk factors such as higher pathological TNM stages and higher tumor grades. Statistical significance of the combined hazard ratio (HR) was detected for CSS (HR, 2.090; 95% CI, 1.530-2.857), RFS (HR = 2.749; 95% CI, 1.974-3.828), MFS (HR = 1.621; 95% CI, 1.095-2.400). However, the association between MVI and worse overall survival did not address statistical significance (HR = 1.371; 95% CI, 0.978-1.923). These findings suggest that the presence of MVI has a detrimental effect on clinicopathological features of RCC and could serve as a poor prognostic factor for patient with RCC.