Uncommon single and compound EGFR mutations: clinical outcomes of a heterogeneous subgroup of NSCLC

Unveiling the Landscape of Uncommon EGFR Mutations in NSCLC-A Systematic Review

Uncommon EGFR mutations represent a rare subgroup of NSCLC. Data on the efficacy of different generations of tyrosine kinase inhibitors (TKIs) in these rare mutations are scattered and limited to mostly retrospective small cohorts because these patients were usually excluded from clinical trials. This was a systematic review on the efficacy of TKIs in patients harboring uncommon EGFR mutations, defined as mutations other than exon 20 insertions mutations or T790M. Response rates (RRs) for different generations of TKIs were determined for individual uncommon mutations, compound mutations, and according to classical-like and P-loop alpha helix compressing mutations classes. This study was conducted in accordance with the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A total of 1836 patients from 38 studies were included in the final analysis. Most available data (92.6%) were from patients treated with first- or second-generation TKIs. G719X, S768I, E709X, L747X, and E709-T710delinsD showed RRs ranging from 47.8% to 72.3% to second-generation TKIs, generally higher than for first- or third-generation TKIs. L861Q mutation exhibited 75% (95% confidence interval [CI]: 56.6%-88.5%) RRs to third-generation TKIs. Compound mutations with G719X, E709X, or S768I consistently showed RRs above 50% to second- and third-generation TKIs, although fewer data were available for third generations. For classical-like mutations, RRs were 35.4% (95% CI: 27.2%-44.2%), 51.9% (95% CI: 44.4%-59.3%), and 67.9% (95% CI: 47.6%-84.1%) to first-, second-, and third-generation TKIs, whereas for P-loop alpha helix compressing mutations classes mutations, RRs were 37.2% (95% CI: 32.4%-42.1%), 59.6% (95% CI: 54.8%-64.3%), and 46.3% (95% CI: 32.6%-60.4%), respectively. This systematic review supports the use of second-generation TKI afatinib for G719X, S768I, E709X, and L747X mutations and for compound uncommon mutations. For other uncommon mutations such as L861Q, third-generation TKI, such as osimertinib, could also be considered, given its activity and toxicity profile.

Successful treatment of lung adenocarcinoma complicated with a rare compound EGFR mutation L833V/H835L using aumolertinib: a case report and literature review

Background: The deletion of exon 19 and the Leu858Arg mutation of exon 21 are the most frequently observed mutations in the epidermal growth factor receptor (EGFR) gene, and patients with these mutations have shown significant benefits from EGFR-tyrosine kinase inhibitors (TKIs). However, there exists a small subgroup of patients with uncommon/rare mutations of EGFR, including compound mutations, which display a high degree of heterogeneity in terms of clinical features and variable sensitivities to EGFR-TKIs. The understanding of these uncommon mutations and their response to targeted therapy is still unclear and requires further investigation. Case presentation: We presented a case of a never-smoking patient with lung adenocarcinoma and brain metastasis. Initially, she received chemotherapy plus immune checkpoint inhibitor as first-line therapy as no EGFR mutations were detected by amplification-refractory mutation system-polymerase chain reaction. However, disease progressed rapidly. Subsequently, next-generation sequencing was carried out and revealed a rare compound mutation, L833V/H835L, in exon 21 of EGFR. As a result, she was switched to second-line therapy with the third-generation TKI aumolertinib, which demonstrated good efficacy. The patient was evaluated for a remarkable progression-free survival of 18 months and an overall survival of 29 months. Conclusion: The present study supports that aumolertinib might be a good treatment option for advanced NSCLC patients with EGFR L833V/H835L mutation, particularly in patients with brain metastasis. Furthermore, conducting a comprehensive screening for gene mutations is crucial in effectively identifying potential oncogenic driver mutations and guiding mutation-targeted therapy decisions in clinical practice.

Uncommon EGFR Compound Mutations in Non-Small Cell Lung Cancer (NSCLC): A Systematic Review of Available Evidence

Compound epidermal growth factor receptor (EGFR) mutations represent a heterogeneous subgroup of non-small cell lung cancer (NSCLC) patients with uncommon EGFR mutations. We conducted a systematic review to investigate the available data on this patients' subgroup. Overall, we found a high heterogeneity in the incidence of compound mutations (4-26% of total EGFR mutant cases), which is dependent on the different testing methods adopted and the specific mutations considered. In addition, the relative incidence of distinct compound subclasses identified is reported with extreme variability in different studies. Preclinical and clinical data, excluding de novoEGFR exon 20 p.T790M compound mutations, show good responses with EGFR tyrosine kinase inhibitors (TKIs) (combined common mutations: response rate (RR) ≥ 75% with either first- or second-generation TKIs; combined common plus uncommon: RR 40-80% and 100% with first-generation TKIs and afatinib, respectively; combined uncommon: RR 20-70%, ~80% and ~75% with first-generation TKIs, afatinib and osimertinib, respectively). Overall, data are consistent in supporting the use of EGFR TKIs in treating compound EGFR mutations, taking into account different sensitivity profile of accompanying EGFR mutations for selecting the most adequate EGFR TKI for individual patients.