Our results indicate that TTF‐1 expression had a meaningful association with both PD‐L1 expression and efficacy of ICI monotherapy in advanced lung adenocarcinoma, suggesting that, in addition to PD‐L1, the assessment of TTF‐1 as a biomarker before ICI treatment may help physicians choose appropriate regimens, such as ICI with or without cytotoxic agents. Here, CD274 is linked to lung adenocarcinoma.