Implications of primary tumor size on overall survival in patients with multifocal T3 non-small cell lung cancer

In patients with non-small cell lung cancer (NSCLC) with T3 multifocal disease (within the same lobe), the prognostic significance of tumor size on overall survival (OS) is unclear. Here, we evaluate the implications of tumor size on OS in patients with multifocal T3 disease without/with limited nodal involvement (N0/N1) in surgical and non-surgical NSCLC. Adults aged ≥ 66 years with newly diagnosed (2010-2015) early and locoregionally-advanced NSCLC (T1‒T3, N0/N1, M0 per the AJCC 8th/9th editions), without prior or concurrent primary cancer, were identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. OS in patients with T3 multifocal disease stratified by primary tumor size (≤ 3 cm [T3-small] vs. > 3 but ≤ 7 cm [T3-large]) was analyzed and compared with those without multifocal disease (T3-unicentric). Among N0 patients who were treated surgically, those with T3-small disease demonstrated improved median OS (months [95% confidence interval]: 86.1 [70.2, 95.9]) vs. those with T3-large and T3-unicentric disease (44.1 [36.4, 52.7] and 51.0 [44.6, 56.8], respectively). Similarly, among the non-surgical N0 patients, those with T3-small disease demonstrated improved median OS (26.7 [22.3, 30.7]) vs. those with T3-large and T3-unicentric disease (14.1 [12.3, 17.2] and 10.9 [10.0, 11.8], respectively). In both surgical and non-surgical cohorts, T3 with N1 disease had similar survival across the subgroups of interest. In patients with T3 multifocal disease without nodal involvement, tumor size is an essential consideration and associated with OS. These findings may warrant reevaluation of the T3 stage classification and inform the evolution of future TNM classifications.