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.

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.