Prognostic impact of PD‐L1 expression in surgically resected EGFR‐mutant lung adenocarcinoma: A real‐world database study in Japan (CReGYT‐01 EGFR study)

The expression of programmed cell death‐ligand 1 (PD‐L1) and mutation in epidermal growth factor receptor (EGFR) are biomarkers used for perioperative treatment of lung adenocarcinoma. However, the clinical significance of PD‐L1 expression in surgically resected EGFR‐mutant lung adenocarcinoma remains unclear. We conducted a real‐world database of patients with surgically resected lung adenocarcinoma from 2015 to 2018 was constructed across 21 centers in Japan. The association among PD‐L1 expression, EGFR mutations, and prognosis was evaluated. Among 847 patients, PD‐L1 expression was negative (tumor proportion score [TPS] < 1%) in 429 (51%), weakly positive (TPS = 1%–49%) in 275 (32%), and strongly positive (TPS ≥50%) in 143 (17%) patients. EGFR mutations were detected in 331 (39%) patients. PD‐L1 expression was associated with poor recurrence‐free survival (RFS) (p < .001) in both EGFR‐mutant and wild‐type patients. However, in EGFR‐mutant patients, PD‐L1 expression was not associated with overall survival (OS) (p = .506). Multivariable analysis confirmed an association between PD‐L1 expression and RFS but not OS. Furthermore, in EGFR‐mutant patients treated with EGFR‐tyrosine kinase inhibitor (EGFR‐TKI) treatment post‐relapse, PD‐L1 expression was not associated with overall response rate (p = .714), disease control rate (p = .554), or progression‐free survival (p = .660). In conclusion, PD‐L1 expression predicted poor RFS‐independent EGFR status but did not show any association with OS in EGFR‐mutant patients. The efficacy of post‐relapse EGFR‐TKI treatment was independent of PD‐L1 expression. The significance of PD‐L1 expression in perioperative EGFR‐TKI therapy should be evaluated.