TTF1 and non-small cell lung carcinoma: The other was a study from Germany on EGFR/ALK-gene-aberration-negative non-small-cell lung cancer [9], which reported that TTF-1-positive cases responded better to regimens with PEM and that TTF-1-negative cases responded better to regimens without PEM; thus, TTF-1 status could be a biomarker for antitumor efficacy.