399P - Prognostic impact of new T1 descriptors in TNM classification of non-small cell lung cancer

Abstract

Background: In the 8th edition of the tumor, node and metastasis (TNM) classification for non-small cell lung cancer (NSCLC), T category is defined by tumor size, only the size of the solid component size on computed tomography (CT) or the size of the invasive component size at pathologic examination. Thus, whether patients with solid tumors should be treated similarly to those with part-solid tumors with solid components of equal size is unclear. In the present study, we assessed the prognostic value of the newly proposed T1 descriptors with regard to solid component size in patients with NSCLC. Methods: We included 255 consecutive patients who were diagnosed with clinical stage IA NSCLC according to the TNM 7th edition, and underwent lobectomies between January 2005 and December 2010 at our medical center. We assessed the prognostic value of the newly proposed T1 descriptors with regard to solid component size. Survival analysis was performed between solid tumor group and part-solid tumor group for all patients and for their propensity score-matched pairs. In addition, the new staging system was used for classification and comparison of survival. Results: Chest CTs found 7 non-solid tumors, 123 part-solid tumors and 125 solid tumors. Mean whole tumor size and maximum diameter of solid components were 20 mm (range: 0–30 mm) and 17 mm (0–30 mm), respectively. Mean duration of follow-up after surgical resection was 59 months. For the entire cohort, the 5-year overall survival (OS) rate was 77.2%, and the 5-year disease-free survival (DFS) rate was 72.1%. The 5-year OS and DFS differed significantly between patients with solid tumors (5-year OS: 71.2%; 5-year DFS: 65.4%) and the part-solid tumor group (5-year OS: 83.2%; 5-year DFS: 78.2%). However, among 81 propensity score-matched pairs, (including matching for solid component size), OS and DFS did not significantly differ between the solid and part-solid tumor groups. Using the 8th TNM edition, 5-year OS rates were patients diagnosed with cIA1 disease: 88.0%; cIA2: 79.4%; and cIA3: 67.6%. Conclusions: The propensity score matching based on solid component size showed no significant difference in survival between the solid and part-solid tumor groups. The 8th edition T descriptors have prognostic value for NSCLC. Legal entity responsible for the study: Tomoyoshi Takenaka Funding: None Disclosure: All authors have declared no conflicts of interest.