Upstaging by vessel invasion improves the pathology staging system of non-small cell lung cancer

Background: There is a need for a more complete classification system of lung cancer. To address this issue, we assessed whether the new staging could differentiate patients with early-stage cancers who have poorer prognosis and improve the unbalanced patient numbers with overlapping prognoses arising from the current TNM staging system. Methods: The study included 995 patients with pathology stages I and II non-small cell lung cancer (NSCLC) who underwent surgical resection at two institutions. We subclassified patients with stage IA and IB NSCLC based on the presence of vessel invasion (Vi). Stage IA Vi and stage IB non-Vi were combined into new stage IB, as were stages IB Vi and IIA into new stage IIA. Results: The numbers of patients of stages IA, IB, IIA, and IIB were 477, 314, 55, and 149, and their 5-year survival rates were 86.0%, 66.2%, 60.7%, and 50.4%, respectively. Vi groups showed significantly poorer prognosis than non-Vi groups at stage IA (p = 0.011) and at stage IB (p = 0.036). The numbers of patients of new stages IA, IB, and IIA were 333, 260, and 253, and their 5-year survival rates were 88.7%, 76.4%, and 61.2%, respectively. Regression analysis indicated that the new staging improved predictability of overall survival according to disease stage, and Akaike information criterion (3023.7) was significantly lower than that for current staging system (3032.5). Conclusion: Upstaging of Vi groups allows differentiation of patients with early-stage cancers with poor prognosis and improves the unbalanced numbers of patients and prediction of prognosis in cases of lung cancer.