Prognostic and Predictive Value of 18F-FDG PET/CT Metabolic Parameters in EGFR-Mutant Lung Adenocarcinoma Treated with Tyrosine Kinase Inhibitors: A Single-Center Retrospective Study with Subgroup Analysis of 19del vs. L858R

Background Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) are the standard first-line treatment for EGFR-mutant lung adenocarcinoma. However, the efficacy and prognosis vary significantly among individuals. This study aimed to investigate the correlation between baseline 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) metabolic parameters and the efficacy of targeted therapy as well as long-term prognosis in patients with EGFR-mutant lung adenocarcinoma, with a specific subgroup analysis for exon 19 deletion (19del) and exon 21 L858R mutation. Methods A total of 175 patients with pathologically confirmed EGFR-mutant lung adenocarcinoma who underwent baseline 18F-FDG PET/CT before EGFR-TKI treatment were retrospectively enrolled. The maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured. The primary endpoints were progression-free survival (PFS) and overall survival (OS). The secondary endpoint was objective response rate (ORR). Kaplan-Meier curves, log-rank tests, and Cox proportional hazards regression models were used for survival analysis. Subgroup analysis was performed according to EGFR mutation subtypes (19del vs. L858R). Results During a median follow-up of 48 months, high SUVmax, MTV, and TLG were significantly associated with shorter PFS and OS (all P < 0.05). Multivariate analysis confirmed that MTV (HR = 1.862, 95% CI: 1.324–2.619, P < 0.001) and TLG (HR = 1.745, 95% CI: 1.248–2.439, P = 0.001) were independent prognostic factors for PFS. In subgroup analysis, the prognostic value of MTV and TLG was more pronounced in the L858R subgroup compared with the 19del subgroup. Conclusions Baseline 18F-FDG PET/CT metabolic parameters, especially MTV and TLG, are valuable independent prognostic biomarkers for EGFR-mutant lung adenocarcinoma patients treated with EGFR-TKIs. The predictive performance differs between 19del and L858R subtypes, which may help guide individualized treatment strategies.