The patients were divided into four groups (A−, A+, B−, B+) according to tumor size (A, ≤ 2 cm; B, 2-3 cm) and VPI status (+, with; −, without). The 5-year OS for groups A− (n = 526), A+ (n = 66), B− (n = 159), and B+ (n = 26) were 77%, 71%, 73%, and 51%, respectively (Fig 2A). The 5-year CIR for groups A−, A+, B−, and B+ were 18%, 16%, 20%, and 40%, respectively (Fig 2B). Among patients with tumors ≤ 2 cm, VPI was not associated with either increased risk of recurrence (P = .90) (Fig 2B) or decreased OS (P = .11) (Fig 2A). However, among patients with tumors 2 to 3 cm, the presence of VPI was associated with both decreased CIR (P = .015) (Fig 2B) and decreased OS (P < .001) (Fig 2A). On the basis of these observations, we then regrouped stage I lung ADC ≤ 3 cm as new stage IA (≤ 2 cm with or without VPI [A+, A−]; 2-3 cm without VPI [B−]) or new stage IB (2-3 cm with VPI [B+]) tumors (Table 3). When the tumors were regrouped by this proposed scheme, there was a statistically significant difference in 5-year CIR and OS between new stage IA (n = 751) and new stage IB (n = 26) tumors (CIR, 18% vs 40% [P = .004]; OS, 76% vs 51% [P < .001]) (Figs 2C, 2D).