KRT19 and Pleural effusion: Cox regression analysis showed that ECOG PS, LDH, cytokeratin 19 fragment (CYFRA21-1) and TFA were factors influencing prognosis (P<0.05).<h4>Conclusions</h4>ECOG PS, pleural effusion and LDH may be risk factors affecting the occurrence of TFA and TFA may be a predictor of the efficacy of immunotherapy.