Modification of Pathological T Classification for Non-small Cell Lung Cancer with Visceral Pleural Invasion: Data from 1,055 Cases of Cancers 3 cm or Less.

BACKGROUND Visceral pleural invasion (VPI) with PL1 or PL2 increases the T classification from T1 to T2 in non-small cell lung cancers (NSCLCs) 3 cm or less. We proposed a modified T classification based on VPI to guide adjuvant therapy. RESEARCH QUESTION Is it reasonable to upstage PL1-positive cases from T1 to T2 for NSCLCs 3 cm or less? STUDY DESIGN AND METHODS In total, 1,055 resected NSCLC patients were retrospectively included. Tumor sections were re-stained with hematoxylin and eosin stain and Vitoria blue's elastic stain for the elastic layer. Disease-free survival (DFS) and overall survival (OS) were calculated by the Kaplan-Meier method. Subgroup analysis and a Cox proportional hazards model were used to further determine the impact of VPI on survival. RESULTS The extent of VPI was diagnosed as PL0 in 824 patients, PL1 in 133 patients, and PL2 in 98 patients. The 5-year DFS rates of patients with PL0, PL1, and PL2 were 62.6%, 60.2%, and 28.8% (P<0.01), respectively, while the corresponding 5-year OS rates were 78.6%, 74.4%, and 50.0% (P<0.01). As predicted, the DFS and OS of PL2 patients were much worse than those of PL0 (P<0.01) and PL1 (P<0.01) patients. However, both the DFS and OS of PL0 and PL1 patients were comparable (DFS, P=0.198; OS, P=0.150). For node-negative cases, the DFS and OS of PL0 and PL1 patients were also comparable (DFS, P=0.468; OS, P=0.388), but PL2 patients again had much worse DFS and OS than PL0 (P<0.01) and PL1 (P<0.01) patients. Multivariable analyses suggested that PL2, together with node positivity and poor cell differentiation, was an independent adverse prognostic factor. INTERPRETATION In NSCLCs 3 cm or less, tumors with PL1 should remain defined as T1, not T2. Overtreatment by adjuvant chemotherapy in node-negative NSCLCs 3 cm or less might be avoided in PL1 cases.