Complete Response to Afatinib of an EGFR Exon 18 delE709_T710insD-Mutated Stage IV Lung Adenocarcinoma

Efficacy of targeted therapy in patients with non-small cell lung cancer harboring very rare mutations in EGFR exon 18

Background

Somatic mutations in epidermal growth factor receptor (EGFR) exon 18 are classified as uncommon or rare mutations in non-small cell lung cancer (NSCLC), in this context, other than G719X or E709X exon 18 mutations are even more rare and heterogeneous. In such scenario, first line treatment options are still debated. The aim of this study was to investigate the response of NSCLC patients harboring very rare exon 18 mutations to EGFR tyrosine kinase inhibitors (EGFR-TKIs).

Methods

This retrospective descriptive study included 105 patients with NSCLC harboring mutations in EGFR exon 18 diagnosed at West China Hospital. The clinical response to EGFR-TKIs was evaluated according to different classifications of mutations in 45 NSCLC patients: 39 harboring G719X or E709X mutations and 6 harboring very rare mutations in EGFR exon 18.

Results

Among 105 patients, 84% (88/105) harbored rare mutations in EGFR exon 18, including G719X and E709X mutations. The remaining 16% (17/105) had very rare mutations in EGFR exon 18, including E709_710delinsX and G724S. For the subsequent efficacy analysis of EGFR-TKI in 45 NSCLC patients, patients harboring very rare mutations achieved a favorable disease control rate (DCR) of 100% and had a median progression-free survival (PFS) of 17.2 months, which was not significantly different compared to patients harboring G719X or E709X (P=0.59).

Conclusions

EGFR-TKIs showed great efficacy in terms of responses and survival in patients harboring exon 18 EGFR rare mutations. This may justify the use of targeted therapies as a potential treatment strategy for these patients.

Response to dacomitinib in advanced non-small-cell lung cancer harboring the rare delE709_T710insD mutation: A case report

BACKGROUND

Tyrosine kinase inhibitors (TKI) have been the standard first-line therapy for advanced non-small cell lung cancer (NSCLC) of epidermal growth factor receptor (EGFR) sensitive mutations. Uncommon EGFR mutations are increasingly reported with the development of next-generation sequencing. However, their sensitivity to TKIs is variable with limited clinical evidence.

CASE SUMMARY

Here, we report a patient with the rare delE709_T710insD mutation, who showed the favorable efficacy of dacomitinib and achieved a partial response with a progression-free survival of 7.0 mo.

CONCLUSION

To our knowledge, this is the first report displaying the clinical efficacy of dacomitinib for patients with delE709_T710insD, which may help to provide alternatives in non-classical variant NSCLC patients. Further studies are warranted to make the optimal choice of EGFR-TKI for rare mutations.