The choice of therapy depends on the mutational landscape of the individual patient\u2019s disease; for example, presence or absence of disease driver mutations in epidermal growth factor receptor (EGFR) or ALK tyrosine kinase receptor (ALK) genes and the programmed death ligand-1 (PD-L1) tumour proportion score (TPS). Immunotherapy with pembrolizumab (an anti-PD-L1 antibody) alone (in patients with metastatic NSCLC with PD-L1 TPS \u2265 50%) or in combination with chemotherapy (regardless of tumour PD-L1 expression) is providing much improved 5-year overall survival rates compared to patients treated with platinum-based chemotherapy. There is also some data that suggest that thyroid transcription factor 1 (TTF-1) expression affects the efficacy of therapy. Expression of TTF-1 is restricted to epithelial cells of the thyroid and lung, and is, therefore, a useful immunohistochemical marker for the diagnosis of tumours of thyroid or lung origin. Also, TTF-1 expression is used in the decision-making process for chemotherapy in lung cancer patients, as it is a positive prognostic factor for the use of pemetrexed or docetaxel. In a recent study Uhlenbruch et al. analysed the effect of expression of TTF-1 in tumour cells on progression-free survival (PFS) of patients with stage 4 lung cancer being treated with chemo-\/immunotherapy (CIT) or immunotherapy with a checkpoint inhibitor (CPI). The study compared four groups of patients: groups 1 and 2 (patients with CPI with and without TTF-1 expression) and groups 3 and 4 (patients with CIT with and without TTF-1 expression) and found that PFS was better in both of groups 1 and 3 (i.e. with TTF-1 expression). Additionally, they found that PFS was significantly affected by antimicrobial treatment one month before the lung cancer treatment in patients with CPI but not in patients with CIT. As the study involved a relatively small number of patients, further validation is needed, but the data suggest that TTF-1 expression could be a useful predictive factor for the use of chemotherapy in combination with PD-L1 and cytotoxic T-lymphocyte antigen 4 (CTLA-4) inhibitor therapy.<\/p>\n