T category of non–small cell lung cancer invading the fissure to the adjacent lobe

Background Dispute arises in the tumor category of non–small cell lung cancer invading the fissure to the adjacent lobe. The purpose of this study is to determine the long-term prognosis of non–small cell lung cancer with such an invasion and to propose an appropriate T category. Methods In total, 53 cases of non–small cell lung cancer invading the fissure to the adjacent lobe (fissure group) were identified in patients who underwent pulmonary resection from 1997 to 2014. Propensity score matching was applied to balance known confounders for prognosis between each paired group, resulting in 3 matched sets (fissure vs T2a, fissure vs T2b, and fissure vs T3). The overall survival of the fissure group was compared with the survival of patients with T2a, T2b, and T3 diseases, as classified in the eighth edition of TNM classification. Results The 5-year survivals of the T2a, T2b, T3, and fissure groups were 64.2% (95% confidence interval, 53.2-72.6), 54.6% (95% confidence interval, 44.7-65.8), 35.8% (95% confidence interval, 22.8-44.2), and 38.6% (95% confidence interval, 25.0-52.2), respectively. Specifically, the difference between the fissure group and T2a is statistically significant at P =.01; between the fissure group and T2b at P =.02; and between the fissure group and T3 at P =.93. Multivariate analyses indicate that the fissure group had a similar risk of dying as the T3 disease group (hazard ratio, 1.10; 95% confidence interval, 0.69-1.37) and was at a significantly higher risk compared with the T2a group (hazard ratio, 2.34; 95% confidence interval, 1.50-3.39) and T2b group (hazard ratio, 1.71; 95% confidence interval, 1.19-2.76). Conclusions On the basis of our single-institution study, we propose that non–small cell lung cancer invading the fissure to the adjacent lobe should be further investigated and the impact on patients’ prognoses validated as a T3 disease.