Abstract: Objective To investigate the effects of different generations of epidermal growth factor receptor tyrosine kinase inhibitors (epidermal growth factor receptor-tyrosine kinase inhibitors, EGFR-TKIs) on peripheral blood RNA 5-methylcytosine (5-methylcytosine, m5C) modification patterns in patients with EGFR-mutant non-small cell lung cancer (non-small cell lung cancer, NSCLC), and to analyze their associations with clinical efficacy and progression-free survival (progression-free survival, PFS).Methods This single-center prospective cohort study consecutively enrolled 86 patients with EGFR-mutant lung adenocarcinoma who underwent surgical resection and were pathologically confirmed at Baoding First Central Hospital between January 2021 and December 2023.According to the postoperative adjuvant EGFR-TKI regimen, patients were divided into an icotinib group (n=42) and a befotertinib group (n=44).Peripheral blood samples were collected on postoperative day 1, after two treatment cycles, and at 6 months of treatment.Global RNA m5C levels and the expression of RNA m5C-related regulatory genes were measured.Dynamic changes in RNA m5C modification during treatment with different generations of EGFR-TKIs were compared, and Cox proportional hazards models were used to evaluate their associations with PFS.Results No significant differences were observed between the two groups in baseline clinical characteristics or baseline peripheral blood RNA m5C levels (P>0.05).During treatment, peripheral blood RNA m5C levels decreased significantly over time in the icotinib group, reaching 0.78±0.17 at 6 months, which was significantly lower than that in the befotertinib group (0.94±0.20, P<0.001).The magnitude of RNA m5C reduction was also greater in the icotinib group (-0.22±0.11 vs.-0.09±0.08, P<0.05).Within the icotinib group, patients who developed disease progression exhibited a significantly larger decline in RNA m5C levels than those without progression (-0.31±0.12 vs.-0.14±0.09, P<0.05).The median follow-up time for the entire cohort was 24.6 months (interquartile range: 18.2-32.4 months).Multivariate Cox regression analysis demonstrated that treatment regimen (hazard ratio=1.72, 95% confidence interval: 1.11-2.67, P=0.015) and a marked decrease in peripheral blood RNA m5C levels (hazard ratio=2.08, 95% confidence interval: 1.34-3.22, P=0.001) were independent predictors of unfavorable PFS.Conclusion Different generations of EGFR-TKIs induce distinct dynamic patterns of peripheral blood RNA m5C modification in patients with EGFR-mutant NSCLC, and a significant decrease in RNA m5C was associated with poor PFS.Dynamic changes in peripheral blood RNA m5C may represent a potential marker of systemic molecular status during treatment, and their clinical utility and tumor specificity require further validation.

Key words: epidermal growth factor receptor tyrosine kinase inhibitor; non-small cell lung cancer; RNA 5-methylcytosine; peripheral blood; progression-free survival