Visceral pleural invasion is not predictive of survival in patients with lung cancer and smaller tumor size

Background: Visceral pleural invasion (VPI) is used as an indicator of adverse prognosis in non-small cell lung cancer (NSCLC). The purpose of this retrospective study was to evaluate the impact of VPI on disease-free survival (DFS) and overall survival (OS) in patients with node-negative NSCLC. Methods: Between 1998 and 2009, 1,166 patients with pathologic N0M0 NSCLC underwent surgical resection by lobectomy. Two hundred fourteen patients with VPI were compared with 952 patients without VPI. Results: Median follow-up was 59 months. In multivariate analysis, VPI, larger tumor size, older age, female sex, and poor performance status were significantly associated with decreased OS. In contrast, larger tumor size, female sex, and poor performance, but notably not VPI, were associated with decreased DFS. After examining interactive effects of VPI and T stage subgroups, we found that VPI did not significantly affect either OS or DFS in the subgroups of patients with smaller tumor sizes - stage T1a, stage T1b, or stage T2a. In contrast, a deleterious effect of VPI on DFS was seen for tumors larger than 5 cm - stages T2b and T3 - with the VPI-stage T3 interaction effect being statistically significant for DFS but not for OS. Conclusions: The effect of VPI on survival in NSCLC varies greatly with tumor size, with VPI not strongly associated with OS or DFS in tumors smaller than 5 cm, but showing large negative effects on DFS for stage T2b and stage T3 tumors. Using VPI to upstage T1 tumors to a higher T stage is not warranted because it would misrepresent these VPI-T stage subgroup effects.