Clinical Efficacy and Safety of First- or Second-Generation EGFR-TKIs after Osimertinib Resistance for EGFR Mutated Lung Cancer: A Prospective Exploratory Study

Detection of Circulating Tumor Cells and EGFR Mutation in Pulmonary Vein and Arterial Blood of Lung Cancer Patients Using a Newly Developed Immunocytology-Based Platform

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are powerful molecular targeted therapeutic agents for lung cancer. We recently developed an original immunocytology and glass slide-based circulating tumor cell (CTC) detection platform for both CTC enumeration and EGFR mutation analysis with DNA extracted from CTCs.

METHODS

Using this platform, we conducted a pilot clinical study for CTC enumeration in peripheral blood (PB), pulmonary arterial blood (PA), and pulmonary venous blood (PV) from 33 patients with lung cancer (Stage I-III) who underwent surgery, followed by digital PCR-based EGFR mutation analysis of CTCs in PV from 12 patients.

RESULTS

The results showed that CTC levels were significantly higher in PV and PA than in PB (p < 0.05, p < 0.01. respectively), with a notably greater number of small and large CTC clusters (p < 0.01). Genetic analysis of EGFR mutations of CTCs from PV (n = 12) revealed six mutations, including three Exon19del and three L856R, in CTCs and eight EGFR mutations, including five Exon19del and three L856R, in lung tumor tissue. CTC mutation status matched that of tissue samples in nine patients, was unmatched in two patients, and controversial in one patient, indicating a sensitivity of 0.75 (6/8) and specificity of 1.0 (4/4) with some false-negative results for the mutation analysis of CTCs.

CONCLUSIONS

This immunocytology-based CTC detection platform is a convenient method for detecting both CTC number and EGFR mutation status under microscopy, suggesting its potential as a liquid biopsy tool in the hospital for patients with lung cancer in some clinical settings.

Mechanism of targeting the mTOR pathway to regulate ferroptosis in NSCLC with different EGFR mutations

Patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR)-activating mutations can be treated with EGFR-tyrosine kinase inhibitors (TKIs). Although EGFR-TKI-targeted drugs bring survival promotion in patients with EGFR mutations, drug resistance is inevitable, so it is urgent to explore new treatments to overcome drug resistance. In addition, wild-type EGFR lacks targeted drugs, and new targeted therapies need to be explored. Ferroptosis is a key research direction for overcoming drug resistance. However, the role and mechanism of regulating ferroptosis in different EGFR-mutant NSCLC types remains unclear. In the present study, H1975 (EGFR T790M/L858R mutant), A549 (EGFR wild-type) and H3255 (EGFR L858R mutant) NSCLC cell lines were used. The expression of ferroptosis markers in these cell lines was detected using western blotting and reverse transcription-quantitative PCR. Cell viability was determined using the MTT assay and reactive oxygen species (ROS) levels were measured using flow cytometry. The results showed that, compared with EGFR wild-type/sensitive mutant cells, EGFR-resistant mutant cells were more sensitive to the ferroptosis inducer, erastin. Furthermore, the mammalian target of rapamycin (mTOR) inhibitor, everolimus (RAD001), induced cell death in all three cell lines in a dose-dependent manner. The ferroptosis inhibitor, ferrostatin-1, could reverse cell death in EGFR-resistant mutant and EGFR wild-type cells induced by RAD001, but could not reverse cell death in EGFR-sensitive mutant cells. Compared with EGFR wild-type/sensitive mutant cells, EGFR-resistant mutant cells were more sensitive to RAD001 combined with erastin. In addition, a high-dose of RAD001 reduced the expression levels of ferritin heavy-chain polypeptide 1 (FTH1), glutathione peroxidase 4 (GPX4) and ferroportin and significantly increased ROS and malondialdehyde (MDA) levels in EGFR-resistant mutant and EGFR wild-type cells. In the present study, GPX4 inhibitor only or combined with RAD001 inhibited the AKT/mTOR pathway in EGFR-resistant mutant cells. Therefore, the results of the present study suggested that inhibition of the mTOR pathway may downregulate the expression of ferroptosis-related proteins in EGFR-resistant and EGFR wild-type NSCLC cells, increase the ROS and MDA levels and ultimately induce ferroptosis.

EGFR-TKI rechallenge in patients with EGFR-mutated non-small-cell lung cancer who progressed after first-line osimertinib treatment: A multicenter retrospective observational study

BACKGROUND

Rechallenge therapy with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) is known to confer some clinical benefit for patients with metastatic EGFR-mutated non-small cell lung cancer (NSCLC). However, little is known about the efficacy of EGFR-TKI rechallenge after resistance to first-line (1L) osimertinib. This study aimed to assess the efficacy and safety of EGFR-TKI rechallenge therapy after resistance to 1L osimertinib in a Japanese clinical setting.

METHODS

Between April 2018 and August 2022, 26 patients who progressed after treatment with 1L osimertinib and received EGFR-TKI rechallenge were included in this multicenter retrospective analysis. Patients in whom 1L osimertinib was discontinued owing to toxicity and had subsequent disease progression were also included in the analysis.

RESULTS

Overall, the objective response rate for rechallenge therapy was 23.1%. The disease control rate was 53.9%, and the median progression-free survival (PFS) was 3.4 months. Patients who discontinued 1L osimertinib for toxicity had a higher response rate (42.9% vs. 15.8%) and longer PFS than those who discontinued it due to disease progression (median: 11.4 vs. 2.7 months, P = 0.001). Three patients (11.5%) developed rechallenge therapy-associated pneumonitis, two of which were grade ≥3.

CONCLUSIONS

Rechallenge with EGFR-TKI after 1L osimertinib resistance showed limited clinical efficacy. However, it could be considered as a subsequent salvage therapeutic option for patients in whom 1L osimertinib was discontinued owing to toxicity.