Biomarker role of thyroid irAE and PD-L1 positivity in predicting PD-1 blockade efficacy in patients with non-small cell lung cancer

Thyroid immune-related adverse events (irAEs) are associated with programmed cell death protein 1 (PD-1) blockade efficacy in non-small cell lung cancer (NSCLC). However, their independence from PD-L1 expression and quantitative impact on predicting PD-1 blockade efficacy remain unexplored. This multicenter, retrospective, longitudinal study from Korea included 71 metastatic NSCLC patients who underwent PD-L1 expression and thyroid function testing during PD-1 blockade. Disease progression by the Response Evaluation Criteria for Solid Tumors was the main outcome. Three-stage analyses were performed: (1) multivariate Cox regression models adjusted for PD-L1 expression according to thyroid irAEs; (2) subgroup analyses; (3) regrouping and comparing predictivity of current and alternative staging. Patients with thyroid irAE + exhibited a longer progression-free survival [7/20 vs. 34/51, adjusted HR 0.19 (0.07–0.47); P < 0.001] than those with thyroid irAE-, independent of PD-L1 expression; the results remained across most subgroups without interaction. The three groups showed different adjusted HR for disease progression (Group 1: PD L1 + and thyroid irAE + ; Group 2: PD-L1 + or thyroid irAE + : 5.08 [1.48–17.34]; Group 3: PD-L1− and thyroid irAE− : 30.49 [6.60–140.78]). Alternative staging (Group 1 in stage IVB → stage IVA; Group 3 in stage IVA → stage IVB) improved the prognostic value (PVE: 21.7% vs. 6.44%; C-index: 0.706 vs. 0.617) compared with the 8th Tumor–Node–Metastasis staging. Our study suggests thyroid irAEs and PD-L1 expression are independent biomarkers that improve predicting PD-1 blockade efficacy in NSCLC. Thyroid irAEs would be helpful to identify NSCLC patients who benefit from PD-1 blockade in early course of treatment.