Evaluation of Treatment Efficacy of Tyrosine Kinase Inhibitors in Rare Single EGFR Exon 21 L861Q Mutation: Single Center Experience.

Objective: Epidermal growth factor receptor mutations are the second most common oncogenic driver event in non-small cell lung cancer. We aimed to compare the first generation erlotinib treatment with the second generation afatinib treatment in patients with non- small cell lung cancer with epidermal growth factor receptor exon 21 L861Q mutation.

Material And Methods: Progression-free survival and overall survival of 30 non-small cell lung cancer patients treated with erlo- tinib or afatinib due to single epidermal growth factor receptor L861Q positivity were compared retrospectively. The number of patients included in the first, second, and third treatment line was 15 (50.0%), 11 (36.7%), and 4 (13.3%), respectively.

Results: There were 23 patients in the erlotinib arm and 7 patients in the afatinib arm. Median progression-free survival was 12.8 months in the erlotinib group and 9.3 months in the afatinib group. Median overall survival in erlotinib and afatinib groups was 77.9 months and 30.3 months, respectively. No statistically significant difference was found in the comparison of these survival times.

Conclusion: Survival times of erlotinib and afatinib treatment are similar in patients with a single epidermal growth factor receptor L861Q mutation. In patients receiving tyrosine kinase inhibitors treatment, the female gender has a positive effect on progression-free survival, and being a non-smoker has a positive effect on overall survival. In patients with rare mutation exon 21 L861Q positivity, both first-generation and second-generation tyrosine kinase inhibitors should be considered.