Prognostic impact of vascular invasion and standardization of its evaluation in stage I non-small cell lung cancer

BACKGROUND: Patients with pathologic stage (p-Stage) IA non-small cell lung cancer (NSCLC) have a good survival rate because of possible curative resection. However, up to 10% of these patients relapse postoperatively. To identify unfavorable prognostic factors, we retrospectively analyzed the clinicopathological features of p-Stage IA disease, focusing on vascular invasion. METHODS: Of 467 patients with p-Stage I NSCLC, 335 were diagnosed with p-Stage IA or IB disease based on a lesion size ≤3 cm and the presence of pleural invasion (PL). Univariate and multivariate analyses of recurrence-free survival (RFS) were performed with age, sex, PL, and vascular invasion (blood vessel invasion [v] and lymphatic vessel invasion [ly]) as variables. To examine vascular invasion, hematoxylin-eosin (HE), Elastica van Gieson staining, and immunostaining with anti-podoplanin antibody were performed. The presence or absence of v and ly was recorded; the number of involved vessels was counted. Survival rates were obtained using the Kaplan–Meier method and log-rank test. Multivariate analyses were performed using the Cox proportional hazards model. RESULTS: RFS differed significantly between patients with no or one involved blood vessel (0 v or 1 v) and those with ≥2 involved vessels (≥2 v). Similarly, RFS differed significantly between patients with no lymphatic vessel involvement (0 ly) and those with one involved lymphatic vessel (1 ly). Thus, BVI(+) and BVI(−) were defined as ≥2 v and 0 v + 1 v, and LVI(+) and LVI(−) as ≥1 ly and 0 ly, respectively. BVI and LVI together represented tumor vessel invasion (TVI). On multivariate analyses, PL and TVI were independently associated with recurrence. Additionally, patients with p-Stage IA TVI(+) disease had a comparable recurrence rate to those with p-Stage IB disease. CONCLUSIONS: Similar to PL, TVI is an important factor increasing the likelihood of recurrence. As HE staining alone is insufficient for evaluating vascular invasion, specific staining is necessary. Moreover, patients with p-Stage IA TVI(+) disease had a recurrence rate comparable to those with p-Stage IB disease; therefore, further studies should aim to elucidate whether patients with p-Stage IA TVI(+) disease should be administered postoperative chemotherapy similar to that received by p-Stage IB patients. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5213064891369688