Efficacy of Osimertinib in Afatinib-resistant Lung Cancer Harboring Uncommon EGFR Mutations: Case Report and Literature Review

Efficacy and potential resistance mechanisms of afatinib in advanced non-small cell lung cancer patients with EGFR G719X/L861Q/S768I

BACKGROUND

Afatinib is the only currently approved EGFR-tyrosine kinase inhibitors for advanced non-small cell lung cancer (NSCLC) patients with EGFR G719X/L861Q/S768I. However, there are limited real-world data concerning the benefits and resistance mechanisms of afatinib in patients with these nonclassical mutations. To fill this gap, the present study was conducted.

METHODS

All NSCLC patients treated with afatinib were screened, and patients with EGFR G719X/L861Q/S768I were enrolled into the analysis. Either tumor tissue or blood specimens were detected by the commercial next-generation sequencing (NGS) panels or amplification-refractory mutation system (ARMS)-polymerase chain reaction (PCR) to figure out the mutation genotype.

RESULTS

A total of 106 advanced NSCLC patients with EGFR G719X/L861Q/S768I received afatinib treatment. The benefits of afatinib exhibited heterogeneity in different mutation genotypes. Notably, at baseline, NGS testing was performed in 59 patients, and TP53 was the most frequently coexisting mutation. Patients with TP53 mutations obtained fewer survival benefits than those with TP53 wild-type. A total of 68 patients ultimately experienced progression, and 27 patients received NGS testing to clarify the potential resistance mechanisms. EGFR-T790M, CDK4 amplification, FGFR1 amplification, PIK3CA, MET amplification, RET fusions, HER2, and BRAF mutations were identified in three (11.1%), three (11.1%), three (11.1%), three (11.1%), three (11.1%), one (3.7%), one (3.7%), and one (3.7%) of the cases, respectively. Five patients underwent ARMS-PCR testing for detecting EGFR-T790M mutation, and only one patient was T790M-positive.

CONCLUSIONS

The present study elucidated the differential benefits of afatinib within different mutation genotypes and first revealed the spectrum of potential resistance mechanisms in patients with EGFR G719X/L861Q/S768I. The results of this study may provide practical clinical information that can guide optimal treatment in this setting.