# Investigation of the Efficacy of Epidermal Growth Factor Receptor (EGFR)-Tyrosine Kinase Inhibitor in Patients With EGFR Exon 21 L858R Point Mutation-Positive Non-small Cell Lung Cancer

## TL;DR

This study examines how well EGFR-TKI therapy works in lung cancer patients with a specific EGFR mutation, finding that PDL1-positive patients may respond poorly and have higher risks of side effects.

## Contribution

The study identifies PDL1 status as a potential predictor of response and risk for interstitial lung disease in patients with EGFR exon 21 L858R mutations.

## Key findings

- 67.7% of patients with EGFR exon 21 L858R mutations responded to EGFR-TKI therapy.
- PDL1-negative patients were more likely to respond to treatment than PDL1-positive patients.
- PDL1-positive patients had a higher risk of developing interstitial lung disease after treatment.

## Abstract

Background: Treatment of advanced non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) has a higher response rate than with conventional chemotherapy in patients positive for EGFR mutations. However, the efficacy of EGFR-TKI therapy may be reduced in patients positive for the EGFR exon 21 L858R point mutation.

Objective: To determine the clinical characteristics of patients with EGFR exon 21 L858R point mutation-positive NSCLC who are non-responders to EGFR-TKI therapy and the factors that predict response to EGFR-TKI therapy.

Methods: Patients with NSCLC treated with EGFR-TKIs were evaluated for response after treatment, and those who responded were compared with those who did not respond.

Results: Of 31 patients, 21 (67.7%) responded to EGFR-TKI therapy (the response group). There were significantly more programmed death ligand 1 (PDL1)-negative patients in the response group than in the non-response group. A significantly higher number of patients in the PDL1-positive group developed interstitial lung disease (ILD) after EGFR-TKI therapy than those in the PDL1-negative group.

Conclusion: EGFR-TKI therapy is likely to be non-responsive in PDL1-positive patients with EGFR exon 21 L858R point mutation-positive NSCLC. The PDL1-positive group is at a high risk of developing ILD.