# Clinical Impact of EGFR Mutation Subtypes on Treatment Outcomes in Advanced Non-Small Cell Lung Cancer: An Austrian Real-World Study

## TL;DR

This study shows that common EGFR mutations in lung cancer patients lead to better survival outcomes when treated with targeted therapies compared to rare mutations.

## Contribution

The study provides real-world evidence on the clinical impact of EGFR mutation subtypes in advanced NSCLC patients in Austria.

## Key findings

- Patients with common EGFR mutations (exon 19 deletion or L858R) had significantly better overall survival than those with uncommon mutations.
- Exon 19 deletion was associated with the longest median overall survival compared to L858R and other mutations.
- Determining EGFR mutation status is crucial for optimizing treatment decisions in NSCLC patients.

## Abstract

The discovery of activating mutations in the epidermal growth factor receptor (EGFR) gene and development of targeted therapies such as EGFR tyrosine kinase inhibitors (TKIs) have had an enormous impact on treatment strategies for advanced non-small cell lung cancer (NSCLC) patients. TKIs are designed to block specific mutations and prevent cancer from growing. In particular, common mutations (exon 19 deletion and L858R point mutation) are strong predictors for favorable survival outcome due to positive treatment response. The present study evaluated real-world survival outcomes of patients with advanced EGFR-mutated NSCLC treated with EGFR TKIs in Austria, with a specific focus on comparing outcomes between patients with common and rare EGFR mutation subtypes outside of clinical trial settings.

Background: Non-small cell lung cancer (NSCLC), particularly in advanced stages, has poor prognosis. The main objective of the study is to evaluate real-world treatment outcomes in advanced NSCLC patients harboring an EGFR mutation and being treated with TKIs. Methods: The EGFR mutation status was ascertained by next-generation sequencing. The observational cohort study used prospectively maintained registry data. Patient data were collected at two high-volume institutions in Austria between November 2020 and February 2025. The prevalence of EGFR mutations was 11% (145 out of 1267 patients). Results: Among 53 patients (stage IIIB or higher) with an EGFR mutation, median overall survival (OS) and median progression-free survival (PFS) were 17.7 months (95% CI: 10.4–24.9) and 14.2 months (95% CI: 7.4–20.9), respectively. A total of 36 patients harbored common EGFR mutations (exon 19 deletion or L858R point mutation) and exhibited a significantly better OS than those with an uncommon EGFR genotype (p < 0.005). Patients with exon 19 deletion (n = 25) showed the longest mOS, followed by those with L858R mutation (32.5 vs. 17 months). In multivariable analysis, the EGFR common mutation subtype (HR = 3.71 95%CI: 1.23–11.2) was associated with better OS. Patients with common EGFR genotypes, especially exon 19 deletion obtained longer OS and PFS compared with those with uncommon mutations in exon 18–21. Conclusions: The results underscore the prognostic role of distinct EGFR genotypes and the urgency of determining the mutation status in non-small cell lung cancer patients to ensure the best treatment decision. The study also highlights the challenges regarding to EGFR uncommon mutations and the resulting need for further research to investigate alternative treatment options.