The alteration of T790M between 19 del and L858R in NSCLC in the course of EGFR-TKIs therapy: a literature-based pooled analysis

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.

Tenovin 3 induces apoptosis and ferroptosis in EGFR 19del non small cell lung cancer cells

Epidermal growth factor receptor (EGFR) exon 19 deletion is a major driver for the drug resistance of non-small cell lung cancer (NSCLC). Identification small inhibitor capable of selectively inhibiting EGFR-19del NSCLC is a desirable strategy to overcome drug resistance in NSCLC. This study aims to screen an inhibitor for EGFR exon 19 deletion cells and explore its underlying mechanism. High through-put screen was conducted to identify an inhibitor for EGFR-19del NSCLC cells. And tenovin-3 was identified as a selective inhibitor of PC9 cells, an EGFR-19del NSCLC cells. Tenovin-3 showed particular inhibition effect on PC9 cells proliferation through inducing apoptosis and ferroptosis. Mechanistically, tenovin-3 might induce the apoptosis and ferroptosis of PC9 cells through mitochondrial pathway, as indicated by the change of VDAC1 and cytochrome c (cyt c). And bioinformatics analyses showed that the expression levels of SLC7A11 and CPX4 were correlated with NSCLC patient's survival. Our findings provide evidences for tenovin-3 to be developed into a novel candidate agent for NSCLC with EGFR exon 19 deletion. Our study also suggests that inducing ferroptosis may be a therapeutic strategy for NSCLC with EGFR exon 19 deletion.

Differential efficacy of tyrosine kinase inhibitors according to the types of EGFR mutations and agents in non-small cell lung cancer: a real-world study

BACKGROUND

Both first and second-generation EGFR-TKIs are recommended in advanced NSCLC with common EGFR mutations. However, there are few data on the difference in efficacy of EGFR-TKIs based on the type of EGFR mutation and agents.

METHODS

This retrospective real-world study evaluated the outcomes and clinicopathologic characteristics, including the type of EGFR mutations, of 237 advanced NSCLC patients treated with first- or second-generation (afatinib) EGFR-TKIs as first-line therapy.

RESULTS

The median progression-free survival (PFS) and overall survival (OS) of all patients were 11 months (M) and 25M, respectively. In the univariate analysis, patients with exon 19 deletion (del) (n=130) had significantly longer median OS compared to those with other mutations (L858R: 84, others: 23) (30 vs. 22 M, p=0.047), without a difference in PFS (p=0.138). Patients treated with afatinib (n=60) showed significantly longer median OS compared to those treated with first-generation TKIs (gefitinib: 159, erlotinib: 18) (30 vs. 23 M, p=0.037), without a difference in PFS (p=0.179). In patients with exon 19 del, there was no significant difference in median PFS (p=0.868) or OS (p=0.361) between patients treated with afatinib and those treated with first-generation TKIs, while significantly better PFS (p=0.042) and trend in OS (p=0.069) were observed in patients receiving afatinib in other mutations. Exon 19 del was independently associated with favorable OS (p=0.028), while age >70 years (p=0.017), ECOG performance status ≥2 (p=0.001), primary metastatic disease (p=0.007), and synchronous brain metastasis (p=0.026) were independent prognostic factors of poor OS.

CONCLUSIONS

The EGFR exon 19 del was associated with favorable OS in advanced NSCLC patients receiving first-line EGFR-TKIs. Moreover, in patients with exon 19 del, first-generation TKIs seem to be a reasonable treatment option if osimertinib is unavailable.

Recruitment of hexahydroquinoline as anticancer scaffold targeting inhibition of wild and mutants EGFR (EGFRWT, EGFRT790M, and EGFRL858R)

Hexahydroquinoline (HHQ) scaffold was constructed and recruited for development of new series of anticancer agents. Thirty-two new compounds were synthesised where x-ray crystallography was performed to confirm enantiomerism. Thirteen compounds showed moderate to good activity against NCI 60 cancer cell lines, with GI % mean up to 74% for 10c. Expending erlotinib as a reference drug, target compounds were verified for their inhibiting activities against EGFRWT, EGFRT790M, and EGFRL858R where compound 10d was the best inhibitor with IC50 = 0.097, 0.280, and 0.051 µM, respectively, compared to erlotinib (IC50 = 0.082 µM, 0.342 µM, and 0.055 µM, respectively). Safety profile was validated using normal human lung (IMR-90) cells. 10c and 10d disrupted cell cycle at pre-G1 and G2/M phases in lung cancer, HOP-92, and cell line. Molecular docking study was achieved to understand the potential binding interactions and affinities in the active sites of three versions of EGFRs.

Liquid biopsy in clinical outcomes and detection of T790M mutation in metastatic non-small cell lung cancer after progression to EGFR-TKI

BACKGROUND

Liquid biopsy (LB) is used to detect epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) and has been demonstrated to have prognostic and predictive value.

OBJECTIVE

To associate the rates of EGFR and T790M mutations detected by LB during disease progression after first- or second-generation EGFR-TKIs with clinical characteristics and survival outcomes.

METHODS

From January 2018 to December 2021, 295 patients with advanced EGFR mutant (EGFRm) NSCLC treated with first- or second-generation EGFR-TKIs were retrospectively analyzed. LB was collected at the time of progression. The frequency of EGFRT790M mutations, overall survival (OS), and the clinical characteristics associated with LB positivity were determined.

RESULTS

The prevalence of EGFRT790M mutation detected using LB was 44%. In patients with negative vs. positive LB, the median OS was 45.0 months vs. 25.0 months (p= 0.0001), respectively. Patients with a T790M mutation receiving osimertinib had a median OS of 44 months (95% CI [33.05-54.99]). Clinical characteristics associated with positive LB at progression extra-thoracic involvement, > 3 metastatic sites, and bone metastases.

CONCLUSIONS

Our findings showed that LB positivity was associated with worse survival outcomes and specific clinical characteristics. This study also confirmed the feasibility and detection rate of T790M mutation in a Latin American population.

Understanding the feasibility of chemotherapeutic and immunotherapeutic targets against non-small cell lung cancers: an update of resistant responses and recent combinatorial therapies

Despite consistent progress in prompt diagnosis and curative therapies in the last decade, lung cancer (LC) continues to threaten mankind, accounting for nearly twice the casualties compared to prostate, breast, and other cancers. Statistics associate ~25% of 2021 cancer-related deaths with LC, more than 80% of which are explicitly caused by tobacco smoking. Prevailing as small and non-small cell pathologies, with respective occurring frequency of nearly 15% and 80-85%, non-small cell LCs (NSCLCs) are prominently distinguished into lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), subtypes. Since the first use of epidermal growth factor receptor (EGFR) inhibitor gefitinib for NSCLC treatment in 2002, immense progress has been made for targeted therapies with the next generation of drugs spanning across the chronological generations of small molecule inhibitors. The last two years have overseen the clinical approval of more than 10 therapeutic agents as first-line NSCLC medications. However, uncertain mutational aberrations as well as systemic resistant responses, and abysmal overall survival curtail the combating efficacies. Of late, immune checkpoint inhibitors (ICIs) against various molecules including programmed cell death-1 (PD-1) and its ligand (PD-L1) have been demonstrated as reliable LC treatment targets. Keeping these aspects in mind, this review article discusses the success of NSCLC chemo and immunotherapies with their characteristic effectiveness and future perspectives.

T790M detection rate after first-line combination therapy with bevacizumab and EGFR-TKIs in advanced NSCLC (TERRA Study)

Real-world data regarding the T790M mutation rate after acquiring resistance to first-line combination therapy with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) and bevacizumab in patients with advanced non-small-cell lung cancer (NSCLC) are limited. The present study was aimed at analyzing predictors of acquired T790M mutations in this patient group. A total of 107 patients who received first-line combination therapy with EGFR-TKIs and bevacizumab at 11 tertiary referral centers in Taiwan were enrolled in this multicenter retrospective study. Survival data and genomic test results after acquiring resistance were analyzed. We discovered that patients who received a combination of afatinib, a second generation EGFR-TKI, and bevacizumab showed better progression-free survival (PFS). After disease progression, 59 patients (55.1%) were confirmed to test positive for EGFR T790M. A longer duration of first-line therapy could be a predictor of subsequent T790M mutations. To our knowledge, this is one of the few and early studies to demonstrate the T790M mutation rate after first-line combination therapy with an EGFR-TKI and bevacizumab. Whether the longer PFS afforded by the addition of bevacizumab could lead to subsequent T790M mutations needs further investigation.

The efficacy of neoadjuvant EGFR-TKI therapy combined with radical surgery for stage IIIB lung adenocarcinoma harboring EGFR mutations: A retrospective analysis based on single center

Background

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) could provide survival benefits for locally advanced EGFR-mutant (EGFRm) non-small cell lung cancer (NSCLC). However, the role of radical surgery for EGFR-TKI treated stage IIIB EGFRm NSCLC remains controversial. This study attempted to assess the feasibility of neoadjuvant EGFR-TKI followed by radical surgery for stage IIIB EGFRm NSCLC.

Patients and Methods

Between 2013 and 2020, EGFRm lung adenocarcinoma (LUAD) patients in clinical stage IIIB undergoing neoadjuvant EGFR-TKI followed by surgery (T-S-Arm) and EGFR-TKI alone (T-Arm) were reviewed retrospectively in Shanghai Pulmonary Hospital (SPH). The chi-square test, Student's t-test or Fisher's exact test was performed for analysis of baseline characteristics. Progression-free survival (PFS) was estimated using the Kaplan-Meier analysis. Multivariate Cox regression analysis was used to identify independent predictors of progression.

Results

A total of 43 patients were divided into T-S-Arm (n = 21) and T-Arm (n = 22). Patients were well-balanced between the two arms. The majority of patients were female (n = 25, 58.1%), non-smokers (n = 35, 81.4%), first-generation of EGFR-TKI treatment (n = 39, 90.7%), and exon 19 deletions (19-DEL) (n = 26, 60.5%). The median diagnostic age was 63.0 years [interquartile range (IQR), 54.0-67.5 years). At the cut-off date with June 30th 2022, median follow-up time was 28 months (IQR, 20-39 months). Neoadjuvant EGFR-TKI treatment followed by radical surgery could significantly improve the median PFS compared with patients underwent EGFR-TKI alone (23.0 months vs 14.5 months, P = 0.002). Multivariate Cox regression analysis demonstrated that radical surgery (T-S-Arm vs. T-Arm, HR: 0.406; 95% CI: 0.207-0.793, P = 0.027) was the only independent predictor for disease progression. The stratified analysis demonstrated patients with N2 disease could benefit from radical surgery (HR, 0.258; 95% CI, 0.107-0.618), especially for patients harboring L858R mutation (HR, 0.188; 95% CI, 0.059-0.604).

Conclusions

For stage IIIB EGFRm NSCLC patients, the prognosis might be improved by neoadjuvant EGFR-TKI followed by radical surgery versus EGFR-TKI alone, especially for those with N2 disease and harboring L858R mutation.

Endobronchial ultrasound-guided re-biopsy of non-small cell lung cancer with acquired resistance after EGFR tyrosine kinase inhibitor treatment

BACKGROUND

Few studies assessed the use of endobronchial ultrasound (EBUS)-guided re-biopsy for detecting the T790M mutation after epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) failure.

METHODS

A total of 2996 EBUS procedures were performed during the study period (January 2019-June 2022). In total, 44 consecutive patients who underwent EBUS-guided re-biopsy (56 procedures) for detecting the T790M mutation were analyzed. The success rates and T790M mutation frequencies were analyzed according to the re-biopsy site and EBUS method. Multivariate logistic regression analyses were used to identify factors affecting the likelihood of the T790M mutation.

RESULTS

The success rates for the mutation analyses using EBUS with a guide-sheath (EBUS-GS), EBUS guided transbronchial needle aspiration (EBUS-TBNA), and EBUS-GS with EBUS-TBNA for re-biopsy were 80.6% (29/36), 93.3% (14/15), and 100% (5/5), respectively. Patients who underwent lymph node biopsy using EBUS-TBNA had an increased rates of the T790M mutation compared with those undergoing lung biopsy using EBUS-GS (EBUS-TBNA, 60.0%; EBUS-GS with EBUS-TBNA, 40.0%; EBUS-GS, 11.1%; p < 0.001). In multivariate analysis, the use of a first-generation EGFR-TKI (odds ratio [OR], 4.29; 95% confidence interval [CI], 1.05-17.58; p = 0.043) was associated with occurrence of the T790M mutation. Re-biopsy of the metastatic site tended to be associated with a higher T790M mutation rate. Mild hemoptysis occurred in 3.6% (2/56) of the patients.

CONCLUSIONS

EBUS-guided re-biopsy can be used for detecting the T790M mutation in patients who failed EGFR-TKI therapy. The T790M mutation frequency differed according to the re-biopsy site. The use of a first-generation EGFR-TKI was an independent predictor of the T790M mutation.

Comparison of the Efficacy of EGFR-TKIs Combined with Antiangiogenic Agents between Patients with Exon 19 Deletion and Patients with Exon 21 Leu858 Arg Mutation: A Systematic Review and Meta-Analysis

Purpose

To compare the efficacy of EGFR-TKIs combined with antiangiogenic agents between non-small cell lung cancer patients with exon 19 deletion and patients with exon 21 Leu858 Arg mutation.

Methods

Electronic databases (PubMed, Embase, and the Cochrane Central Register of Controlled Trials) were systematically searched for studies published until March 2022. Randomized control trials comparing the survival of EGFR-TKIs plus antiangiogenic agents with EGFR-TKI were extracted. The primary endpoint was progression-free survival (PFS).

Results

Five randomized control trials involving 1533 patients were as follows: 818 patients had exon 19 deletion, and 715 patients with exon 21 Leu858 Arg mutation. The methodological quality of the 5 randomized control trials was high. EGFR-TKIs plus antiangiogenic agents improved PFS in patients with exon 19 deletion (hazard ratio [HR] = 0.62, 95% confidence interval [CI]: 0.51–0.75) and exon 21 Leu858 Arg mutation (HR = 0.61, 95% CI: 0.50–0.75). PFS did not differ between the exon 19 deletion and exon 21 Leu858 Arg mutation groups (Z = 0.07, P=0.94).

Conclusions

PFS was comparable between patients receiving EGFR-TKIs combined with antiangiogenic agents with exon 19 deletion and those with exon 21 Leu858 Arg mutation.

First-line therapeutic strategy for patients with advanced non-small cell lung cancer with Leu858Arg epidermal growth factor receptor mutations: a Bayesian network meta-analysis

Aim

The objective of this network meta-analysis was to determine the most useful first-line therapeutic strategy for patients with advanced (IIIB/IV or relapsed) non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) Leu858Arg or EGFR 19del mutations.

Methods

PubMed, the Web of Science, Medline, and reports of the top three world cancer conferences (WCLC, ESMO, and ASCO) were searched for appropriated randomized controlled studies (RCTs) discussing the use of various generations of tyrosine kinase inhibitors (TKIs; gefitinib, erlotinib, icotinib, afatinib, dacomitinib, osimertinib, aumolertinib), chemotherapy [pemetrexed-based chemotherapy (PC), non-pemetrexed-based chemotherapy (NPC)], and different combined therapies (osimertinib plus bevacizumab, afatinib plus cetuximab, erlotinib plus bevacizumab, erlotinib plus ramucirumab, gefitinib plus apatinib, gefitinib plus PC, and gefitinib plus pemetrexed) to treat patients with advanced NSCLC with EGFR Leu858Arg or 19del mutations. OpenBugs and Stata software were used to analyze the data.

Results

We included 21 studies with 16 arms (including 2479 cases with EGFR Leu858Arg mutations and 3325 cases with EGFR 19del mutations). Among patients with NSCLC with EGFR Leu858Arg mutations, compared with the first-generation TKIs (such as gefitinib), the second- or third-generation TKIs [dacomitinib: hazard ratio (HR) = 0.63; 95% confidence index (CI) = (0.45, 0.89); osimertinib: HR = 0.63; 95% CI = (0.42, 0.97)] showed significant benefits in improving progression-free survival (PFS), as did afatinib plus cetuximab [HR = 1.98; 95% CI = (1.01, 3.95)], erlotinib plus bevacizumab [HR = 1.79; 95% CI = (1.22, 2.62)], and erlotinib plus ramucirumab [HR = 1.62; 95% CI = (1.07, 2.48)]. In terms of overall survival (OS), these 16 arms showed no significant differences between each other (p > 0.05). Among patients with NSCLC with EGFR 19del mutations, compared with the first- or second-generation TKIs (such as gefitinib and afatinib), aumolertinib [versus gefitinib: HR = 0.39; 95% CI = (0.28, 0.55) versus afatinib: HR = 0.53; 95% CI = (0.35, 0.84)] and osimertinib [versus gefitinib: HR = 0.40; 95% CI = (0.32, 0.51) versus afatinib: HR = 0.53, 95% CI = (0.38, 0.79)] showed significantly beneficial effects. Among these first-line therapeutic strategies for patients with EGFR Leu858Arg mutations, the combination of afatinib and cetuximab ranked as the best to prolong PFS (33.0%). For NSCLC patients with 19del mutations, however, osimertinib plus bevacizumab was the best at prolonging PFS (84.3%).

Conclusion

For NSCLC patients with EGFR Leu858Arg mutations, the second-generation TKIs, the third-generation TKIs, and the combined treatments showed better efficacy than the first-generation TKIs for PFS. There were, however, no significant differences between each group for OS.

Liquid Biopsy: A Multi-Parametric Analysis of Mutation Status, Circulating Tumor Cells and Inflammatory Markers in EGFR-Mutated NSCLC

The liquid biopsy has the potential to improve patient care in the diagnostic and therapeutic setting in non-small cell lung cancer (NSCLC). Consented patients with epidermal growth factor receptor (EGFR) positive disease (n = 21) were stratified into two cohorts: those currently receiving EGFR tyrosine kinase inhibitor (TKI) therapy (n = 9) and newly diagnosed EGFR TKI treatment-naïve patients (n = 12). Plasma genotyping of cell-free DNA was carried out using the FDA-approved cobas® EGFR mutation test v2 and compared to next generation sequencing (NGS) cfDNA panels. Circulating tumor cell (CTC) numbers were correlated with treatment response and EGFR exon 20 p.T790M. The prognostic significance of the neutrophil to lymphocyte ratio (NLR) and lactate dehydrogenase (LDH) was also investigated. Patients in cohort 1 with an EGFR exon 20 p.T790M mutation progressed more rapidly than those with an EGFR sensitizing mutation, while patients in cohort 2 had a significantly longer progression-free survival (p = 0.04). EGFR exon 20 p.T790M was detected by liquid biopsy prior to disease progression indicated by computed tomography (CT) imaging. The cobas® EGFR mutation test detected a significantly greater number of exon 20 p.T790M mutations (p = 0.05). High NLR and derived neutrophil to lymphocyte ratio (dNLR) were associated with shorter time to progression and worse survival outcomes (p < 0.05). High LDH levels were significantly associated with shorter time to disease progression (p = 0.03). These data support the use of liquid biopsy for monitoring EGFR mutations and inflammatory markers as prognostic indicators in NSCLC.

Intratumor heterogeneity of driver mutations and TMB distribution in 30 early-stage LUAD patients with multiple lesions

Background

Differentiating multiple pulmonary lesions as multiple primary lung cancer (MLC) or intra-pulmonary metastasis (IPM) is critical. Lung cancer also has a high genetic heterogeneity, which influenced the treatment strategy. Genetic information may aid in tracing lineage information on multiple lung lesions. This study applied comprehensive genomic profiling to decipher the intrinsic genetics of multiple lung lesions.

Methods

Sixty-six lung adenocarcinomas (LUAD) tumor lesions (FFEP) archived from 30 patients were included in this study. The 508 cancer-related genes were evaluated by targeted next-generation sequencing (MGI-seq 2000).

Results

The study included a total of 30 LUADs (66 samples). The majority of tumors demonstrated intra-tumoral heterogeneity. Two hundred twenty-four mutations were detected by sequencing the 66 samples. We investigated the driver gene mutations of NSCLC patients with multiple lesions. EGFR was the most frequently (48/198) mutated driver gene. The codons in EGFR mainly affected by mutations were p.L858R (18/66 [27.3%]) and exon 19del (8/66 [12.1%]). In addition, additional driver genes were found, including TP53, BRAF, ERBB2, MET, and PIK3CA. We also found that the inter-component heterogeneity of different lesions and more than two different mutation types of EGFR were detected in seven patients with two lesions (P3, P10, P24, P25, P28, P29, and P30). The TMB values of different lesions in each patient were different in 26 patients (except P4, P5, P14, and P30).

Conclusions

Comprehensive genomic profiling should be applied to distinguishing the nature of multiple lung lesions irrespective of radiologic and histologic diagnoses.

Can CT Radiomics Detect Acquired T790M Mutation and Predict Prognosis in Advanced Lung Adenocarcinoma With Progression After First- or Second-Generation EGFR TKIs?

Objective

To explore the potential of CT radiomics in detecting acquired T790M mutation and predicting prognosis in patients with advanced lung adenocarcinoma with progression after first- or second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy.

Materials and Methods

Contrast-enhanced thoracic CT was collected from 250 lung adenocarcinoma patients (with acquired T790M mutation, n = 146, without mutation, n = 104) after progression on first- or second-generation TKIs. Radiomic features were extracted from each volume of interest. The maximum relevance minimum redundancy and the least absolute shrinkage and selection operator (LASSO) regression method were used to select the optimized features in detecting acquired T790M mutation. Univariate Cox regression and LASSO Cox regression were used to establish the radiomics model to predict the progression-free survival of osimertinib treatment. Finally, nomograms (which) combined clinical factors with radscore to predict the acquired T790M mutation and prognosis were built separately. In addition, the two nomograms were validated by the concordance index (C-index), decision curve analysis (DCA), and calibration curve analysis where appropriate.

Results

Clinical factors including the progression-free survival of first-line EGFR TKIs, EGFR mutation, and N stage and 12 radiomic features were useful in predicting the acquired T790M mutation. The area under the receiver operating characteristic curves (AUC) of clinical, radiomics, and nomogram models were 0.70, 0.74, and 0.78 in the training set and 0.71, 0.71, and 0.76 in the validation set, respectively. The DCA and calibration curve analysis demonstrated a good performance of the nomogram model. Clinical factors including age and first-generation EGFR TKIs and 12 radiomic features were useful in patients’ outcome prediction. The C-index of the combined nomogram was 0.686 in the training set and 0.630 in the validation set, respectively. Calibration curves demonstrated a relatively poor performance of the nomogram model.

Conclusion

Nomogram combined clinical factors with radiomic features might be helpful to detect whether patients developed acquired T790M mutation or not after progression on first- or second-generation EGFR TKIs. Nomogram prognostic model combined clinical factors with radiomic features might have a limited value in predicting the survival of patients harboring acquired T790M mutation treated with osimertinib.

EGFR signaling pathway as therapeutic target in human cancers

Epidermal Growth Factor Receptor (EGFR) enacts major roles in the maintenance of epithelial tissues. However, when EGFR signaling is altered, it becomes the grand orchestrator of epithelial transformation, and hence one of the most world-wide studied tyrosine kinase receptors involved in neoplasia, in several tissues. In the last decades, EGFR-targeted therapies shaped the new era of precision-oncology. Despite major advances, the dream of converting solid tumors into a chronic disease is still unfulfilled, and long-term remission eludes us. Studies investigating the function of this protein in solid malignancies have revealed numerous ways how tumor cells dysregulate EGFR function. Starting from preclinical models (cell lines, organoids, murine models) and validating in clinical specimens, EGFR-related oncogenic pathways, mechanisms of resistance, and novel avenues to inhibit tumor growth and metastatic spread enriching the therapeutic portfolios, were identified. Focusing on non-small cell lung cancer (NSCLC), where EGFR mutations are major players in the adenocarcinoma subtype, we will go over the most relevant discoveries that led us to understand EGFR and beyond, and highlight how they revolutionized cancer treatment by expanding the therapeutic arsenal at our disposal.

Risk Stratification Using a Novel Nomogram for 2190 EGFR-Mutant NSCLC Patients Receiving the First or Second Generation EGFR-TKI

Simple Summary

No comprehensive and simple prognostic model based on pretreatment factors exists for patients with epidermal growth factor receptor mutation-positive (EGFRm+) non-small cell lung cancer (NSCLC) undergoing EGFR-tyrosine kinase inhibitors (EGFR-TKIs). A total of 11 independent prognostic factors were identified by multivariate analysis, including performance status, morphology, mutation, stage, EGFR-TKIs, and metastasis to liver, brain, bone, pleura, adrenal gland, and distant lymph nodes. We established a nomogram based on independent pretreatment factors and used it to stratify EGFRm+ NSCLC patients undergoing EGFR-TKI treatment into five different risk groups for survival using recursive partitioning analysis. The performance of this nomogram was good and feasible, providing clinicians and patients with additional information for evaluating therapeutic options.

Abstract

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the standard treatment for EGFR mutation-positive (EGFRm+) non-small cell lung cancer (NSCLC). This study aimed to create a novel nomogram to help physicians suggest the optimal treatment for patients with EGFRm+ NSCLC. Records of 2190 patients with EGFRm+ NSCLC cancer who were treated with EGFR-TKIs (including gefitinib, erlotinib, and afatinib) at the branches of a hospital group between 2011 and 2018 were retrospectively reviewed. Their clinicopathological characteristics, clinical tumor response, progression-free survival (PFS), and overall survival (OS) data were collected. Univariate and multivariate analyses were performed to identify potential prognostic factors to create a nomogram for risk stratification. Univariate analysis identified 14 prognostic factors, and multivariate analysis confirmed the pretreatment independent factors, including Eastern Cooperative Oncology Group performance status, morphology, mutation, stage, EGFR-TKIs (gefitinib, erlotinib, or afatinib), and metastasis to liver, brain, bone, pleura, adrenal gland, and distant lymph nodes. Based on these factors, a novel nomogram was created and used to stratify the patients into five different risk groups for PFS and OS using recursive partitioning analysis. This risk stratification can provide additional information to clinicians and patients when determining the optimal therapeutic options for EGFRm+ NSCLC.

Biomarker subset analysis of a phase IIIb, open-label study of afatinib in EGFR tyrosine kinase inhibitor-naive patients with EGFRm+ non-small-cell lung cancer

Aim: To explore the relationship between mutations in cfDNA and response to afatinib. Patients & methods: In total, 64 patients from one Chinese site with locally advanced/metastatic EGFRm+ non-small-cell lung cancer, who received afatinib 40 mg once daily, were included. Results: Overall, 33 (82.5%) patients became EGFRm- by visit 3; median progression-free survival was longer in these patients vs those who did not (11.0 vs 5.5 months). Progression-free survival was shorter in 42 (45.2%) patients with non-EGFR co-mutations at baseline vs those without (8.1 vs 12.5 months). Neither difference was significant. Conclusion: Afatinib provided clinical benefit for patients with EGFRm+ non-small-cell lung cancer across all subgroups. EGFRm status assessment in plasma cfDNA is a useful method of monitoring treatment.

Acquired Resistance to Third-Generation EGFR Tyrosine Kinase Inhibitors in Patients With De Novo EGFRT790M-Mutant NSCLC

INTRODUCTION

EGFR^T790M mostly exists subclonally and is acquired as the most common mechanism of resistance to EGFR tyrosine kinase inhibitors (TKIs). Nevertheless, because de novo EGFR^T790M-mutant NSCLC is rare, little is known on acquired resistance mechanisms to third-generation EGFR TKIs.

METHODS

Acquired resistance mechanisms were analyzed using tumor and plasma samples before and after third-generation EGFR TKI treatment in four patients with de novo EGFR^T790M-mutant NSCLC. Genetic alterations were analyzed by whole-exome sequencing, targeted sequencing, fluorescence in situ hybridization, and droplet digital PCR. MTOR^L1433S, confirmed for oncogenicity using the Ba/F3 system, was reproduced in H1975 cell lines using CRISPR/Cas9-RNP.

RESULTS

Of seven patients with NSCLC with de novo EGFR^T790M/L858R mutation, four (LC1-4) who received third-generation EGFR TKIs acquired resistance after achieving a partial response (median = 27 mo, range: 17-48 mo). Novel MTOR^L1433S and EGFR^C797S/L798I mutations in cis, MET amplification, and EGFR^C797S mutation were identified as acquired resistance mechanisms to third-generation EGFR TKIs. The MTOR^L1433S mutation was oncogenic in Ba/F3 models and revealed resistance to osimertinib through AKT signaling activation in NCI-H1975 cells harboring the MTOR^L1433S mutation edited by CRISPR/Cas9 (half-maximal inhibitory concentration, 800 ± 67 nM). Osimertinib in combination with mTOR inhibitors abrogated acquired resistance to osimertinib.

CONCLUSIONS

Activation of bypass pathways and the EGFR^C797S or EGFR^C797S/L798I mutation were identified as acquired resistance mechanisms to third-generation EGFR TKIs in patients with NSCLC with de novo EGFR^T790M mutation. In addition, MTOR^L1433S- and EGFR^L858R/T790M-mutant NSCLC cells were sensitive to osimertinib plus mTOR inhibitors.

Comparative Efficacy and Safety of TKIs Alone or in Combination With Antiangiogenic Agents in Advanced EGFR-Mutated NSCLC as the First-Line Treatment: A Systematic Review and Meta-Analysis

BACKGROUND

Several studies have suggested that patients with epidermal growth factor receptor (EGFR)-mutated non-small-cell lung cancer (NSCLC) might benefit from the use of tyrosine kinase inhibitors (TKIs) in combination with antiangiogenic agents. This study aimed to comprehensively review the available evidence regarding the efficacy and safety of first-line TKI plus antiangiogenic agents versus TKIs alone in EGFR-mutated advanced NSCLC.

MATERIALS AND METHODS

A literature search was performed using PubMed to identify studies published up to Feb. 2020. Abstracts from major international conferences reported over the last 5 years were searched. The primary outcome was progression-free survival (PFS), and the secondary outcomes included overall survival (OS), the objective response rate (ORR), and toxicity.

RESULTS

In total, 7 relevant trials comprising 1612 patients were identified. TKIs plus antiangiogenic agents led to significant improvements in PFS regardless of the EGFR mutation subtype and presence of brain metastasis. In particular, in the subgroup with the L858R mutation, the hazard ratio (HR) of PFS was 0.58 (95% confidence interval [CI], 0.48-0.71, P < .001). The OS following combined treatment was similar to that following TKI monotherapy. The ORR was increased with the use of TKIs plus antiangiogenic agents (HR 1.10, 95% CI, 1.01-1.20, P = .029). In the safety analyses, TKIs plus antiangiogenic agents exhibited a significantly increased incidence of adverse events of grade 3 or higher.

CONCLUSION

The use of TKIs plus antiangiogenic agents is associated with significantly improved PFS and ORR compared with TKIs alone in untreated EGFR-mutated NSCLC. The toxicities of combination therapy should be considered when making treatment choices.

Detection and quantification of EGFR T790M mutation in liquid biopsies by droplet digital PCR

Background

Liquid biopsy allows the identification of targetable cancer mutations in a minimally invasive manner. In patients with advanced non-small cell lung cancer (NSCLC), droplet digital PCR (ddPCR) is increasingly used to genotype the epidermal growth factor receptor (EGFR) gene in circulating cell-free DNA (cfDNA). However, the sensitivity of this method is still under debate. The aim of this study was to implement and assess the performance of a ddPCR assay for detecting the EGFR T790M mutation in liquid biopsies.

Methods

A ddPCR assay was optimized to detect the EGFR T790M mutation in plasma samples from 77 patients with NSCLC in progression.

Results

Our ddPCR assay enabled the detection and quantification of the EGFR T790M mutation at cfDNA allele frequency as low as 0.5%. The mutation was detected in 40 plasma samples, corresponding to a positivity rate of 52%. The number of mutant molecules per mL of plasma ranged from 1 to 6,000. A re-biopsy was analyzed for 12 patients that had a negative plasma test and the mutation was detected in 2 cases. A second liquid biopsy was performed for 6 patients and the mutation was detected in 3 cases.

Conclusions

This study highlights the value of ddPCR to detect and quantify the EGFR T790M mutation in liquid biopsies in a real-world clinical setting. Our results suggest that repeated ddPCR tests in cfDNA may obviate tissue re-biopsy in patients unable to provide a tumor tissue sample suitable for molecular analysis.

Generation of osimertinib-resistant cells from epidermal growth factor receptor L858R/T790M mutant non-small cell lung carcinoma cell line

BACKGROUND

Lung cancer contributes to high cancer mortality worldwide with 80% of total cases diagnosed as non-small cell lung cancer (NSCLC). Epidermal growth factor receptor (EGFR) tyrosine kinase (TK) domain serves as a druggable target in NSCLC patients with exon 19 deletion and L858R mutation. However, patients eventually succumbed to resistance to first- and second-generation EGFR-TK inhibitors through activation of T790M mutation. Third-generation EGFR-TKI, Osimertinib exhibits high efficacy in patients with exon 19 deletion/L858R/T790M mutation but they experienced acquired resistance thereafter. Available treatment options in NSCLC patients remains a challenge due to unknown molecular heterogeneity responsible for acquired resistance to EGFR-TKI. In this study, we aim to generate Osimertinib-resistant (OR) cells from H1975 carrying L858R/T790M double mutation which can be used as a model to elucidate mechanism of resistance.

METHODS

OR cells were established via stepwise-dose escalation and limiting single-cell dilution method. We then evaluated Osimertinib resistance potential via cell viability assay. Proteins expression related to EGFR-signalling, epithelial to mesenchymal transition (EMT), and autophagy were analyzed via western blot.

RESULTS

OR cell lines exhibited increased drug resistance potential compared to H1975. Distinguishable mesenchymal-like features were observed in OR cells. Protein expression analysis revealed EGFR-independent signaling involved in the derived OR cells as well as EMT and autophagy activity.

CONCLUSION

We generated OR cell lines in-vitro as evidenced by increased drug resistance potential, increased mesenchymal features, and enhanced autophagy activity. Development of Osimertinib resistance cells may serve as in-vitro model facilitating discovery of molecular aberration present during acquired mechanism of resistance.

Clinical impact of rebiopsy among patients with epidermal growth factor receptor-mutant lung adenocarcinoma in a real-world clinical setting

Background

In this study, we investigated the risk factors of acquired T790M mutation among patients with lung adenocarcinoma with epidermal growth factor receptor (EGFR) tyrosine mutation who were treated with EGFR‐tyrosine kinase inhibitors (TKIs). The aim was to identify the clinical impact of rebiopsy.

Methods

This multicenter, retrospective cohort study was conducted in South Korea from January 2007 to June 2017. Patients with adenocarcinoma with EGFR mutation who underwent rebiopsy and were treated with EGFR‐TKIs were included.

Results

Of a total of 352 patients, T790M mutation was identified in 156 (41.9%) at the time of rebiopsy. The median duration from initial biopsy to rebiopsy was 17 months. Univariate logistic regression analysis revealed associations of exon 19 deletion (odds ratio [OR], 1.643; p = 0.026), absence of L858R (OR, 0.627; p = 0.042), and previous EGFR‐TKI treatment duration (OR, 1.039; p < 0.001) with T790M mutation. Previous EGFR‐TKI treatment duration (OR, 3.580; p < 0.001) was independently associated with T790M mutation. A multivariate Cox proportional hazard model revealed that brain metastasis at initial diagnosis (hazard ratio, 1.390; p = 0.050) tended to be associated with T790M mutation. Among the patients with T790M mutation at rebiopsy, the osimertinib user group (n = 90) had a better one‐year survival (68.7 vs. 58.3%, p = 0.048) than the osimertinib nonuser group (n = 66).

Conclusions

Rebiopsy might affect the clinical course of patients with EGFR‐mutant adenocarcinoma who receive EGFR‐TKIs.

The Impact of Acquired EGFR T790M Mutation and EGFR Circulating Cell-Free DNA on Survival in Patients with Lung Adenocarcinoma Following EGFR-TKI Therapy

Objective

To utilize liquid biopsy to investigate the potential clinical factors influencing the incidence of the acquired epidermal growth factor receptor (EGFR) T790M mutation, and the impact of EGFR circulating cell-free DNA (CfDNA) on overall survival for patients with advanced EGFR-mutated adenocarcinoma resistant to first-line EGFR-tyrosine kinase inhibitor (TKI).

Methods

A retrospective study was conducted to analyze EGFR-mutated stage IIIB-IV adenocarcinoma patients who received an EGFR-TKI (gefitinib, erlotinib, or afatinib) as first-line therapy and then underwent a liquid biopsy exam at disease progression.

Results

A total of 135 patients were included, and the T790M mutation was detected in 51 patients (37.7%). The incidence of T790M mutation increased with the number of initial metastatic sites (p = 0.015). Liver metastasis (odds ratio [OR], 3.373; p = 0.017) and other metastasis (OR, 3.063; p = 0.023) were also independently correlated with T790M mutation incidence. T790M mutation was also associated with more than two progressive sites (OR, 3.382; p = 0.006), liver progression (OR, 6.204; p = 0.002), and bone progression (OR, 3.366; p = 0.004). However, central nervous system progression was inversely correlated with T790M mutation (OR, 0.183; p = 0.027). Overall survival was the longest among the patients without CfDNA, followed by those shedding T790M mutation and those shedding Del 19/L858R mutations (p = 0.005).

Conclusion

Initial metastasis to the liver and other sites may be independent factors for secondary EGFR T790M mutation. T790M-positive lung adenocarcinoma has specific progression patterns. Moreover, not having EGFR CfDNA, being positive for Del19/L858R mutations, and being positive for T790M mutation have differing impacts on overall survival for patients with advanced EGFR-mutated adenocarcinoma resistant to first-line EGFR-TKI.

Concomitant Mutations in EGFR 19Del/L858R Mutation and Their Association with Response to EGFR-TKIs in NSCLC Patients

Objective

Differences in efficacy of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) have been observed between non-small cell lung cancer (NSCLC) patients with 19 exon deletion (19Del) and L858R mutation. We explored whether the total number or pattern of concomitant mutations of 19Del and L858R may explain their different sensitivities.

Patients and Methods

This study contained the mutational profiles of EGFR-mutated NSCLC patients from two cohorts: Guangzhou (G1) and database (G2). Concomitant mutation status and EGFR-TKI response information were retrieved.

Results

A total of 403 patients covered 283 genes in the G1 and 803 patients with a different gene set in the G2 were included. Similar prevalence of total concomitant mutation number was observed in both G1 (19Del 32.48% vs L858R 30.45%; P=0.68) and G2 (19Del 74.9% vs L858R 73.2%; P=0.65) cohorts. Only HGF/c-Met pathway same more related to L858R mutation. EGFR-TKI response information was recorded for 134 patients in the G2 cohort. 19Del showed a higher objective response (OR) rate compared with L858R, regardless of concomitant mutations. Compared to patients with OR, non-OR patients had more concomitant mutations, both in 19Del (53.8% vs 83.3%; P=0.021) and L858R (51.4% vs 77.8%; P=0.029). In particular, total concomitant mutations (OR=0.27; P=0.03), sensitive EGFR mutations (OR=2.21; P=0.04), and T790M (OR=0.244; P=0.02) significantly affected the TKI response.

Conclusion

Concomitant mutations were widespread in 19Del and L858R and were associated with poorer OR to EGFR-TKIs. However, 19Del and L858R had similar numbers and patterns of concomitant mutations, which might not explain the different sensitivity to EGFR-TKI.

Refined Stratification Based on Baseline Concomitant Mutations and Longitudinal Circulating Tumor DNA Monitoring in Advanced EGFR-Mutant Lung Adenocarcinoma Under Gefitinib Treatment

INTRODUCTION

The optimal treatment for EGFR-mutant lung adenocarcinoma (LUAD) remains challenging because of intratumor heterogeneity. We aimed to explore a refined stratification model based on the integrated analysis of circulating tumor DNA (ctDNA) tracking.

METHODS

ctDNA was prospectively collected at baseline and at every 8 weeks in patients with advanced treatment-naive EGFR-mutant LUAD under gefitinib treatment enrolled in a phase 2 trial and analyzed using next-generation sequencing of a 168-gene panel.

RESULTS

Three subgroups categorized by baseline comutations-EGFR-sensitizing mutations (59, 32.8%), EGFR-sensitizing mutations with tumor suppressor mutations (97, 53.9%), and EGFR-sensitizing mutations with other driver mutations (24, 13.3%)-exhibited distinct progression-free survival (13.2 [11.3-15.2] versus 9.3 [7.6-10.5] versus 4.0 [2.4-9.3] months) and overall survival (32.0 [29.2-41.5] versus 21.7 [19.3-27.0] versus 15.5 [10.5-33.7] months, respectively), providing evidence for initial stratification. A total of 63.7% of the patients achieved week 8 ctDNA clearance, with significant difference noted among the three subgroups (74.5% versus 64.0% versus 29.4%, respectively, p = 0.004, Fisher's exact test). Patients without week 8 ctDNA clearance had worse progression-free survival (clearance versus nonclearance 11.2 [9.9-13.2] versus 7.4 [5.6-9.6] months, p = 0.016, Cox regression], especially in the second subgroup [5.8 (5.6-11.5) months], suggesting the necessity of adaptive stratification during treatment. During follow-up, 56.0% and 20.8% of the patients eventually harbored p.T790M and non-p.T790M mutations, respectively, with a significant difference in non-p.T790M mutations among the three subgroups (7.5% versus 15.7% versus 80.0%, respectively, p < 0.001, Fisher's exact test), giving clues to postline treatment.

CONCLUSIONS

The patients with baseline comutations and ctDNA nonclearance at first visit might require combined therapy because of the limited survival benefit of EGFR tyrosine kinase inhibitor monotherapy. We proposed a refined stratification mode for the whole-course management of EGFR-mutant LUAD.

An Observational Study of Acquired EGFR T790M-Dependent Resistance to EGFR-TKI Treatment in Lung Adenocarcinoma Patients in Taiwan

In Taiwan, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs), gefitinib, erlotinib, and afatinib are served as first-line therapy for non-small lung cell cancer (NSCLC) patients with EGFR sensitizing mutations. However, the majority of patients who initially respond to EGFR-TKIs, progress through acquiring EGFR T790M mutations (T790M), which is the most common resistant mechanism. Patients with T790M gain the opportunity of subsequent treatment with third-generation EGFR-TKI, osimertinib. This study aimed to evaluate the association between prior EGFR-TKI therapy and incidence of acquired T790M resistance in lung adenocarcinoma patients who have progressed on first/second-generation EGFR-TKI therapy. This retrospective study included lung adenocarcinoma patients who had a radiographically-confirmed progressive disease under EGFR-TKI treatment and had re-biopsy samples for T790M testing from seven medical centers in Taiwan from June 2013 to December 2018. Patients harboring de novo T790M or using more than one EGFR-TKI were excluded. Of the 407 patients enrolled, the overall T790M acquisition rate was 52.8%. The patients treated with gefitinib, erlotinib or afatinib had a statistically significant difference in the T790M rates (59.9, 45.5, and 52.7%, respectively; p = 0.037) after disease progression. Patients with common baseline EGFR mutations (Del-19 and L858R) (p = 0.005) and longer treatment duration with EGFR-TKIs (p < 0.001) had higher chances of T790M acquisition. Multivariate logistic regression analysis further showed that patients with common baseline EGFR mutations, gefitinib (compared to erlotinib) administration, and longer treatment duration with EGFR-TKIs had higher T790M incidence. There was no significant difference in the incidence of acquired T790M between different re-biopsy tissue samples or complications. In conclusion, this study showed that patients who progressed from gefitinib treatment, bearing common EGFR mutations, and with longer EGFR-TKI treatment duration had increased incidence of T790M acquisition and, therefore, were suitable for subsequent osimertinib treatment.

Clinical implication and usefulness of de novo EGFR T790M mutation in lung adenocarcinoma with EGFR-tyrosine kinase inhibitor sensitizing mutation

In total, 102 cases diagnosed as lung adenocarcinoma with EGFR-tyrosine kinase inhibitor (TKI) sensitizing mutations (mEGFR) and had been treated with 1^st ~ 2^nd generation EGFR-TKI alone were enrolled for this study. De novo T790 M status was tested using the tissues at the initial diagnosis and positivity was defined as the ratio of T790 M/wild-type copies over 0.00294 by ddPCR.

Seventy patients (68.6%) harbored the de novo T790 M. De novo T790 M was more frequently detected in cases with EGFR L858 R mutation than those with EGFR exon 19 deletion (E19d) mutations (P = 0.024). Forty-three patients underwent rebiopsy due to disease progression. The cases who experienced progression due to acquired T790 M were more likely to have E19d at initial diagnosis and the presence of de novo T790 M and the ratio of T790 M/wild-type copies did not relate to the emergence of acquired T790 M. On the other hand, the cases with a longer duration of disease-control by EGFR-TKI had higher change to get acquired T790 M mutation (P-value = 0.040).

The presence of de novo T790 M has limitation in predicting disease progression by acquired T790 M, suggesting that identifying de novo T790 M through the ultrasensitive methods may not be necessary identifying patients who would be beneficial by 3rd-generation EGFR-TKI as the 1st line treatment.

Clinical implementation of plasma EGFR T790M testing using droplet digital PCR in TKI-resistant NSCLC patients

BACKGROUND

Majority of non-small cell lung cancer (NSCLC) patients progressed on epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) due to acquired T790M mutation. Blood sample is increasingly used in clinical setting for EGFR T790M detection and our laboratory employed the droplet digital PCR (ddPCR) methodology for testing. This study investigated the positive rate, specimen type for rebiopsy and clinical impact of blood-based EGFR T790M testing.

METHODS

We retrospectively evaluated clinical samples that underwent plasma EGFR T790M testing in TTSH Molecular Diagnostic Laboratory from August 2017 to September 2019. Data on diagnosis, EGFR activating and T790M mutations, and treatment strategies were recorded.

RESULTS

A total of 104 progressive NSCLC cases were included in this study. Overall, 46 patients (44.2%) were tested T790M positive, and 47.8% of these tested positive had low levels (defined as ≤3% fractional abundance and <50 copies/mL plasma), which may be missed by the conventional methods with lower sensitivity. Of these tested with low T790M abundance, 77.3% subsequently received osimertinib. Activating mutations were not detected in 42 (40.4%) cases, indicating that the tumors were not actively shedding ctDNA. Among these, 24 patients underwent repeat testing with tissue or blood specimens. Thirteen patients were subsequently tested T790M positive and 12 of them switched treatment to osimertinib. The recommendation to repeat testing with a different biopsy or after a suitable interval increased the overall positive rate to 56.7% (59/104).

CONCLUSION

The use of a highly sensitive platform such as ddPCR for the detection of low abundance T790M, and the approach of repeat testing in cases with insufficient ctDNA increased the positive rate. This in turn identified more patients who are eligible for targeted therapy.

EGFR mutation genotypes affect efficacy and resistance mechanisms of osimertinib in T790M-positive NSCLC patients

Background

Osimertinib is a potent third-generation EGFR tyrosine kinase inhibitor (TKI) with robust activity in advanced EGFR-mutant non-small cell lung cancer (NSCLC), including those with T790M resistance mutation. However, a broad interpatient variability was observed. This study aimed to evaluate whether EGFR-mutant genotypes affect the clinical outcomes and resistance mechanisms in T790M-positive NSCLC patients receiving osimertinib therapy.

Methods

All NSCLC patients treated with osimertinib in our institute were screened. We included those with known EGFR-mutant genotypes and T790M positivity. Clinical outcomes including objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS), and overall survival (OS), were evaluated and compared between different EGFR genotypes. Patients with next-generation sequencing testing or tumor rebiopsy after osimertinib treatment were analyzed for resistance mechanisms.

Results

ORR, CBR, PFS, and OS were all non-significantly different among patients harboring EGFR exon 19 deletion (19Del, n=136), L858R (n=93), and uncommon mutations (n=6). However, a subset of tumors with deletion starting at E746 (ΔE746, n=98), but not non-ΔE746 tumors (n=38), had better clinical outcomes than L858R tumors (n=93). Frequencies of T790M loss and C797S acquisition after osimertinib treatment were similar between 19Del (n=56) and L858R tumors (n=33). However, compared with L858R tumors (n=33), those with 19Del ΔE746 subtype (n=40) had a higher whereas non-ΔE746 subtype (n=16) had a similar frequency of acquired C797S mutation. Combined analysis of our cohort and public cohort confirmed these findings.

Conclusions

Our findings indicate that the EGFR 19Del subtypes affect the clinical outcomes and resistance mechanisms to osimertinib in T790M-positive patients. Identifying patients with relatively worse treatment outcomes may be informative for establishing new therapies for these patients.

Detection of Low-level EGFR c.2369 C > T (p.Thr790Met) Resistance Mutation in Pre-treatment Non-small Cell Lung Carcinomas Harboring Activating EGFR Mutations and Correlation with Clinical Outcomes

Increasing evidence points to the presence of low-level de novo T790M mutations in patients with non-small cell lung carcinoma (NSCLC) harboring activating EGFR mutations. We utilized digital PCR (dPCR), a highly sensitive gene mutation detection method, to detect pre-treatment T790M mutations in NSCLC tumor samples and correlated the T790M status with clinical features and patient outcomes. DNA extracted from pre-treatment NSCLC tumor tissue with known activating EGFR mutations, diagnosed between October 2010 and May 2017 at PathWest laboratory, was used to perform targeted dPCR for quantitative detection of T790M mutations. T790M was detected in 42 of 109 pre-treatment samples (38.5%). Median variant allele frequency was 0.14% (range 0.02-28.5%). Overall response rate to first generation EGFR tyrosine kinase inhibitors (TKI) was 67% regardless of T790M status. The median progression free survival was 10.7 (IQR 5.6-19.9) versus 6.7 (IQR 3.5-20.8) months in T790M negative and positive patients respectively. T790M positivity correlated with increased rate of early disease progression. It also correlated with increased mortality (HR 3.1 95%CI 1.2-8.1, p = 0.022) in patients who did not respond to TKI treatment. We detected a significant rate of low-level pre-treatment T790M mutations in NSCLC using highly sensitive dPCR. Low-level pre-treatment T790M did not impact treatment response rate or overall survival, but was associated with increased rate of early progression on TKI therapy.

Prevalence of the EGFR T790M and other resistance mutations in the Australian population and histopathological correlation in a small subset of cases

We sought to review the prevalence of EGFR T790M and other EGFR mutations associated with either proven or probable tyrosine kinase inhibitor (TKI) resistance in the Australasian lung cancer population and to perform histopathological correlation in a subset of cases. Retrospective statistical analysis was performed on a set of targeted lung cancer gene mutation tests (FIND IT gene panel) performed at Sonic Healthcare during 2018 and early 2019. A total of 1833 lung adenocarcinoma tumour samples underwent somatic mutation testing. EGFR mutations were found in 28% (n=514) of patients, in whom 9.3% (n=48) T790M mutations were present (always combined with other EGFR mutations) and 4.8% (n=25) exon 20 insertions were found. We also compared the prevalence of EGFR mutations identified in our population with that of the four largest publicly available lung cancer cohorts (total n=576 samples). Finally, a subset of 38 samples of primary/and or metastatic lung adenocarcinomas from 23 patients, including five with serial biopsies, underwent detailed morphological analysis. No reproducible morphological correlates were found to be associated with T790M, exon 20 resistance mutations or rarer co-occurring EGFR mutations. Although this may be subject to referral bias towards patients with resistant disease, the incidence of EGFR and T790M mutations is higher in this series from an Australasian population than in other similar publicly available lung adenocarcinoma cohorts. We conclude that histopathological features cannot be used to predict the acquisition of EGFR resistance.

Epidermal growth factor receptor tyrosine kinase inhibitors in advanced nonsmall cell lung cancer: what is the preferred first-line therapy?

PURPOSE OF REVIEW

Epidermal growth factor receptor (EGFR) mt+ nonsmall cell lung cancer (NSCLC) were the first molecularly described NSCLC with an established 'targeted' therapy inhibiting mutated EGFR [EGFR tyrosine kinase inhibitor (TKI)]. EGFR TKI of first and second generation have led to an unprecedented improvement in objective response rate, progression-free survival (PFS) and overall survival (OS) compared with chemotherapy with a significantly reduced toxicity and improved quality of life. Fast elucidation of the most frequent resistance mechanism against first and second-generation TKI, T790M, led to the approval of the third-generation TKI osimertinib in second line.

RECENT FINDINGS

Recently, the FLAURA study showed an impressive PFS benefit and immature OS data for osimertinib against solely first-generation TKI's. Also, the ARCHER study comparing dacomitinib against first-generation TKI showed a PFS and also OS benefit. Two studies combining EGFR TKI and antiangiogenesis showed PFS but no OS benefit. Lately, the combination of TKI and chemotherapy has seen a revival with the NEJ009 study, resulting in an impressive median OS of 55 months.

SUMMARY

Therefore, potentially four different therapeutic options are available in first-line therapy of EGFR mt+ NSCLC, first, second, third generation, TKI + antiangiogenic agent and TKI + chemotherapy. The purpose of the review is to help to guide physicians to decide in their treatment choice and discuss potential directions of research.

Incidence of T790M in Patients With NSCLC Progressed to Gefitinib, Erlotinib, and Afatinib: A Study on Circulating Cell-free DNA

BACKGROUND

Insights into the mechanism of resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) could provide important information for further patient management, including the choice of second-line treatment. The EGFR T790M mutation is the most common mechanism of resistance to first- and second-generation EGFR TKIs. Owing to its biologic relevance in the response of non-small-cell lung cancer (NSCLC) to the selective pressure of treatment, the present study investigated whether the occurrence of T790M at progression differed among patients receiving gefitinib, erlotinib, or afatinib.

PATIENTS AND METHODS

The present retrospective study included patients with NSCLC with an EGFR activating mutation, who had received gefitinib, erlotinib, or afatinib as first-line treatment. Plasma samples for the analysis of cell-free DNA were taken at disease progression and analyzed using a digital droplet polymerase chain reaction EGFR mutation assay.

RESULTS

A total of 83 patients were enrolled; 42 had received gefitinib or erlotinib and 41afatinib. The patient characteristics were comparable across the 2 groups. The median time to progression (TTP) was 14.4 months for the gefitinib and erlotinib group and 10.2 months for the afatinib group (P = .09). Of the 83 patients, 47 (56.6%) were positive for the T790M in plasma. A greater incidence of T790M was observed in patients with progression during gefitinib or erlotinib therapy compared with patients treated with afatinib (33 [79%] vs. 14 [34%], respectively; odds ratio, 7.1; 95% confidence interval, 2.7-18.5; P = .0001).

CONCLUSIONS

Although gefitinib, erlotinib, and afatinib showed a comparable TTP in patients receiving first-line therapy, the incidence of T790M differed among them, as demonstrated by the present study, which could have implications for the choice of second-line treatment.

EGFR T790M detection rate in lung adenocarcinomas at baseline using droplet digital PCR and validation by ultra-deep next generation sequencing

Background

Routine testing of baseline EGFR T790M mutation may have important clinical impact but many discordant data have been reported regarding the diagnostic, prognostic and predictive role of this marker. In this study we aimed to assess T790M frequency in 164 untreated EGFR-mutated NSCLCs using methods with different sensitivity as well as to analyze the relationship between baseline T790M mutation status, patient's clinicopathologic features and tyrosine kinase inhibitors (TKI) treatment outcomes.

Methods

We compared the diagnostic performance, sensitivity and specificity of three methods, namely MALDI-TOF mass spectrometry (MS), Allele-Specific Real Time PCR (AS-PCR), droplet digital PCR (ddPCR). Ultra-deep next generation sequencing (NGS) validation of T790M-mutant NSCLCs was performed using SiRe^® panel.

Results

Baseline T790M occurred in 17% of the tumors. Intermediately sensitive techniques such as MALDI-TOF MS (detection limit of T790M ≥5%) allow to detect T790M in 2% of cases exhibiting mutant-allele fractions ranging from 11.5% to 17%. Median overall survival (OS) in these patients was poor (7.3 months) and progression free survival (PFS) was of 3.3 months in patients treated with a 1st generation EGFR TKI. The remaining T790M-positive cases showed very low mutant-allele fractions ranging from 0.07% to 0.38% and required highly sensitive methods such as ddPCR and NGS to be identified. All these cases showed a concurrent sensitizing EGFR mutation (mainly exon 19 deletion), and clinicopathological features similar to those observed in EGFR mutant cancers. Median OS of these patients was 27 months while median PFS after TKI treatment was 20 months.

Conclusions

Routine test of baseline EGFR T790M may have an important role in the prediction to EGFR TKI therapy response and should be performed using highly sensitive and quantitative methods, such as ddPCR and NGS, in order to reliably distinguish NSCLCs with high or very low T790M mutant-allele fraction.

Comprehensive analysis of EGFR T790M detection by ddPCR and ARMS-PCR and the effect of mutant abundance on the efficacy of osimertinib in NSCLC patients

Background

Patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations often develop systemic disease progression during treatment with EGFR-tyrosine kinase inhibitors (TKIs). Droplet digital polymerase chain reaction (ddPCR) and amplification refractory mutation system (ARMS)-PCR are routinely applied for detection of EGFR mutations, including T790M, which is associated with TKI sensitivity. We compared the efficiency of ddPCR and ARMS-PCR in detecting T790M and explored the association between T790M abundance and osimertinib efficacy.

Methods

Genomic DNA (gDNA) from tissue and cells in hydrothorax and circulating tumor DNA (ctDNA) from peripheral blood (PB), and clinicopathological data were retrospectively collected from 263 patients who visited Sun Yat-sen University Cancer Center for T790M test.

Results

Mean T790M abundance and mutant copy number of cases tested positive by both methods, i.e., the ddPCR+ARMS+ group (19.1%, 636.9), were higher than those in the ddPCR+ARMS- group (0.36%, 12.1), suggesting that ddPCR is more sensitive in detecting samples with low mutant abundance than ARMS-PCR. T790M detection rate was comparable for gDNA and ctDNA samples (44.7% vs. 37.6%, P=0.242); however, gDNA sample tended to show more T790M abundance in ddPCR analysis. T790M coexisted with L858R mutation (8/11) more than with deletions in exon 19 (19del) mutation (3/11) in TKI-naive tumors, while 19del co-occurred as often as L858R in post-TKI tumors. T790M+ patients benefited more from osimertinib and showed longer progression-free survival (PFS) (not achieved vs. 10.1 months, P=0.0399), while lower T790M abundance (<1.065%) was associated with longer PFS (not achieved vs. 8.8 months, P=0.0033).

Conclusions

ddPCR has a higher sensitivity than ARMS-PCR, especially in detecting the less abundant T790M. Although detection rates were comparable for ctDNA and gDNA samples, the mutation abundance was higher in gDNA sample. Finally, low T790M abundance was associated with longer PFS in NSCLC patients receiving osimertinib treatment.

Repeat biopsy procedures and T790M rates after afatinib, gefitinib, or erlotinib therapy in patients with lung cancer

OBJECTIVES

Afatinib, a second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), is used for EGFR-mutant non-small cell lung cancer (NSCLC). However, there are few reports about its resistance mechanisms. The aims of this study are to evaluate resistance mechanisms of afatinib compared with other TKIs and analyze the performance of repeat biopsy which is critical for subsequent treatment.

MATERIALS AND METHODS

We screened EGFR-mutant NSCLC patients who started first-line afatinib, gefitinib, or erlotinib from 2014 to 2016, and included patients who acquired resistance. Among those patients, T790 M mutation rates and histologic transformation were compared as an acquired resistance mechanism.

RESULTS

A total of 524 patients started EGFR-TKIs, and 347 experienced disease progression until April 2018. After excluding nine patients with de novo T790 M mutations or who were treated with two TKIs before repeat biopsy, 338 patients were included. Among these patients, 263 (78%) were successfully biopsied and evaluated for EGFR mutations and histologic transformation. T790 M mutation was documented in 35 (41%) of 86 evaluable patients in afatinib group, which is significantly lower than in gefitinib (55%, 73/133) and erlotinib groups (57%, 25/44) (p =  0.026). In multivariate analysis considering both baseline EGFR mutation types (deletion 19 or L858R) and sex, the odds ratio for T790M in afatinib group was 0.45 (95% confidence interval: 0.254-0.795, p =  0.006), compared with gefitinib or erlotinib groups. Five histologic transformations (two small cell, three squamous cell) were detected in afatinib group, while one small cell transformation was detected in gefitinib group, and no transformations were detected in erlotinib group.

CONCLUSIONS

In our clinical practice, repeat biopsy was possible in nearly four of five patients. Although T790 M mutation appears to be the main resistance mechanism for afatinib, it affects a lower proportion of patients than observed with first-generation TKIs.