T1 (≤ 3 cm) tumors with visceral pleural invasion (VPI) are upstaged to T2a (stage IB) in the TNM classification. We investigated the effect of VPI on the cumulative incidence of recurrence (CIR) and overall survival (OS) of lung adenocarcinoma (ADC) ≤ 2 cm (T1a) and 2 to 3 cm (T1b).

OS and CIR among patients with or without VPI were examined by tumor size (≤ 2 and 2-3 cm) in 777 patients with node-negative lung ADC ≤ 3 cm who underwent resection.

Among patients with tumors ≤ 2 cm, VPI was not associated with either increased CIR (P = .90) or decreased OS (P = .11). Among patients with tumors 2 to 3 cm in size, the presence of VPI was associated with increased CIR (P = .015) and decreased OS (P < .001), even after adjusting for histologic subtype. When stage I lung ADCs ≤ 3 cm were regrouped as either new stage IA (≤ 2 cm with or without VPI, 2-3 cm without VPI) or new stage IB (2-3 cm with VPI), there was a statistically significant difference in 5-year CIR and OS between new stage IA and new stage IB tumors (CIR, 18% vs 40% [P = .004]; OS, 76% vs 51% [P < .001]).

VPI stratifies prognosis in patients with lung ADC 2 to 3 cm but not in those with tumors ≤ 2 cm. Our proposed regrouping of a new stage IB better stratifies patients with poor prognosis, similar to published outcomes in patients with stage II disease, who may benefit from adjuvant chemotherapy.