Abstract 5221: TTF-1 status in early-stage lung adenocarcinoma is an independent predictor of relapse and survival superior to tumor grading
Authors: Schallenberg Simon , Dernbach Gabriel , Dragomir Mihnea , Schlachtenberger Georg , Boschung Kyrill , Friedrich Corinna , Standvoss Kai , Ruff Lukas , Anders Philipp , Grohe Christian , Randerath Winfried , Merkelbach-Bruse Sabine , Quaas Alexander , Heldwein Matthias , Keilholz Ulrich , Hekmat Khosro , Rückert Jens , Büttner Reinhard , Horst David , Klauschen Frederick , Frost Nikolaj 
Published: March 2024

Abstract
Background: Thyroid transcription factor 1 (TTF-1) is expressed in 70% to 80% of lung adenocarcinomas (LUAD). Several papers revealed that TTF-1 expression is associated with better patient outcomes independent of the tumor stage. However, it is unknown whether the prognostic impact of TTF-1 only results from a different growth pattern (tumor grading) or is independently associated with a biologically more aggressive phenotype. Thus, we analyzed a large bi-centric cohort of LUAD to assume the true prognostic value of TTF-1 in relation to the tumor grade.
Methods: We collected a large, real-life cohort of 447 patients with completely resected LUAD from two large-volume German lung cancer centers. TTF-1 status, evaluated by IHC, and tumor grading were correlated with clinical, pathologic, and molecular data, as well as patient outcomes. Kaplan-Meier curves were used for comparison of TTF-1 status and different tumor grades in terms of the DFS. The impact of TTF-1 was measured by univariate and multivariate Cox regression. Finally, a causal graph analysis was performed to identify and account for potential confounders to improve the statistical estimation of the predictive power of TTF-1 expression for DFS in comparison to the tumor grade.
Results: Kaplan-Meier curves revealed that TTF-1 positivity is associated with longer DFS independent of tumor grade, whereas a strong association of DFS with the tumor grade is observed only in TTF-1-positive patients. In univariate analysis, TTF-1 positivity was associated with significantly longer DFS (median log HR -0.83 [-1.43; -0.20]; p=0.018), whereas higher tumor grade showed a non-significant association with shorter DFS (median log HR 0.30 [-0.58; 1.60]; p=0,62 for G1 to G2 and 0.68 [-0.24; 1.89]; p=0,34 for G2 to G3). In multivariate analysis, TTF-1 positivity resulted in a significantly longer DFS (median log HR -0.65 [-1.13; -0.09]; p=0.05) independent of all other parameters, including tumor grade. Applying the adjustment sets suggested by the causal graph analysis, the superiority of TTF-1 (median log HR -0.86 [-1.25; -0.41]) over tumor grade (median log HR 0.31 [-0.32; 1.30]/0.61[-0.07; 1.65]) in terms of prognostic power was confirmed.
Conclusion: This study draws three important conclusions: Firstly, it indicates that the prognostic power of tumor grade is limited to TTF-1-positive patients. Secondly, it underlines the independent prognostic value of TTF-1 expression for DFS regardless of tumor grade. Finally, our analyses reveal that the effect size of TTF-1 surpasses that of tumor grade. To transfer the results directly into the clinical area, we recommend distinguishing between TTF-1-positive and TTF-1-negative LUADs in the pathological report. Tumor grading should only be applied to TTF-1-positive LUADs (TTF-1+/G1-3). TTF-1-negative LUADs should either not be graded or always be classified as high-grade (TTF-1-/G3).
Citation Format: Simon Schallenberg, Gabriel Dernbach, Mihnea Dragomir, Georg Schlachtenberger, Kyrill Boschung, Corinna Friedrich, Kai Standvoss, Lukas Ruff, Philipp Anders, Christian Grohe, Winfried Randerath, Sabine Merkelbach-Bruse, Alexander Quaas, Matthias Heldwein, Ulrich Keilholz, Khosro Hekmat, Jens Rückert, Reinhard Büttner, David Horst, Frederick Klauschen, Nikolaj Frost. TTF-1 status in early-stage lung adenocarcinoma is an independent predictor of relapse and survival superior to tumor grading [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5221.