Poor prognostic factors in patients with stage IB non-small cell lung cancer according to the seventh edition TNM classification

Background: This study investigated poor prognostic factors in patients with stage IB non-small cell lung cancer (NSCLC) according to the seventh edition of the TNM classification. Methods: Between July 1992 and December 2004, 1,204 consecutive patients with stage I NSCLC diagnosed based on the sixth edition TNM classification underwent complete resection with systematic node dissection. Of these patients, 434 were reclassified as stage IB according to the seventh edition TNM classification. Univariate analyses were performed using the log-rank test to select prognostic factors. The Cox proportional hazards regression model was used for multivariate analyses to identify independent factors indicating an unfavorable prognosis. Results: On multivariate analyses, two variables were independent significant factors indicating an unfavorable prognosis: presence of intratumoral vascular invasion and presence of visceral pleural invasion. According to subgroup analyses combining these two risk factors, 5-year disease-specific survival probabilities were 93%, 83%, and 73% for patients with zero, one, or two risk factors, respectively. The 5-year disease-specific survival of patients without risk factors was not statistically different from that of patients with stage IA cancer. In addition, the 5-year disease-specific survival curve of patients with two risk factors lay beneath that of patients with T2b or T3N0M0, stage II cancer, and there were no statistically significant differences between them. Conclusions: We identified the presence of intratumoral vascular invasion and the presence of visceral pleural invasion as independent poor prognostic factors in patients with stage IB NSCLC. When these two factors are combined, higher- and lower-risk subgroups can be identified, which will help to personalize adjuvant chemotherapy.