Detection of EGFR-Activating and T790M Mutations Using Liquid Biopsy in Patients With EGFR-Mutated Non-Small-Cell Lung Cancer Whose Disease Has Progressed During Treatment With First- and Second-Generation Tyrosine Kinase Inhibitors: A Multicenter Real-Life Retrospective Study

Machine learning-based radiomics strategy for prediction of acquired EGFR T790M mutation following treatment with EGFR-TKI in NSCLC

The epidermal growth factor receptor (EGFR) Thr790 Met (T790M) mutation is responsible for approximately half of the acquired resistance to EGFR-tyrosine kinase inhibitor (TKI) in non-small-cell lung cancer (NSCLC) patients. Identifying patients at diagnosis who are likely to develop this mutation after first- or second-generation EGFR-TKI treatment is crucial for better treatment outcomes. This study aims to develop and validate a radiomics-based machine learning (ML) approach to predict the T790M mutation in NSCLC patients at diagnosis. We collected retrospective data from 210 positive EGFR mutation NSCLC patients, extracting 1316 radiomics features from CT images. Using the LASSO algorithm, we selected 10 radiomics features and 2 clinical features most relevant to the mutations. We built models with 7 ML approaches and assessed their performance through the receiver operating characteristic (ROC) curve. The radiomics model and combined model, which integrated radiomics features and relevant clinical factors, achieved an area under the curve (AUC) of 0.80 (95% confidence interval [CI] 0.79-0.81) and 0.86 (0.87-0.88), respectively, in predicting the T790M mutation. Our study presents a convenient and noninvasive radiomics-based ML model for predicting this mutation at the time of diagnosis, aiding in targeted treatment planning for NSCLC patients with EGFR mutations.

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.

Application value of CT radiomic nomogram in predicting T790M mutation of lung adenocarcinoma

BACKGROUND

The purpose of this study was to develop a radiomic nomogram to predict T790M mutation of lung adenocarcinoma base on non-enhanced CT lung images.

METHODS

This retrospective study reviewed demographic data and lung CT images of 215 lung adenocarcinoma patients with T790M gene test results. 215 patients (including 52 positive) were divided into a training set (n = 150, 36 positive) and an independent test set (n = 65, 16 positive). Multivariate logistic regression was used to select demographic data and CT semantic features to build clinical model. We extracted quantitative features from the volume of interest (VOI) of the lesion, and developed the radiomic model with different feature selection algorithms and classifiers. The models were trained by a 5-fold cross validation strategy on the training set and assessed on the test set. ROC was used to estimate the performance of the clinical model, radiomic model, and merged nomogram.

RESULTS

Three demographic features (gender, smoking, emphysema) and ten radiomic features (Kruskal-Wallis as selection algorithm, LASSO Logistic Regression as classifier) were determined to build the models. The AUC of the clinical model, radiomic model, and nomogram in the test set were 0.742(95%CI, 0.619-0.843), 0.810(95%CI, 0.696-0.907), 0.841(95%CI, 0.743-0.938), respectively. The predictive efficacy of the nomogram was better than the clinical model (p = 0.042). The nomogram predicted T790M mutation with cutoff value was 0.69 and the score was above 130.

CONCLUSION

The nomogram developed in this study is a non-invasive, convenient, and economical method for predicting T790M mutation of lung adenocarcinoma, which has a good prospect for clinical application.

Can Liquid Biopsy Based on ctDNA/cfDNA Replace Tissue Biopsy for the Precision Treatment of EGFR-Mutated NSCLC?

More and more clinical trials have explored the role of liquid biopsy in the diagnosis and treatment of EGFR-mutated NSCLC. In certain circumstances, liquid biopsy has unique advantages and offers a new way to detect therapeutic targets, analyze drug resistance mechanisms in advanced patients, and monitor MRD in patients with operable NSCLC. Although its potential cannot be ignored, more evidence is needed to support the transition from the research stage to clinical application. We reviewed the latest progress in research on the efficacy and resistance mechanisms of targeted therapy for advanced NSCLC patients with plasma ctDNA EGFR mutation and the evaluation of MRD based on ctDNA detection in perioperative and follow-up monitoring.

Different Liquid Biopsies for the Management of Non-Small Cell Lung Cancer in the Mutational Oncology Era

In the last ten years, liquid biopsy has been slowly joining the traditional invasive techniques for the diagnosis and monitoring of tumors. Liquid biopsies allow easy repeated sampling of blood, reflect the tumor scenario, and make personalized therapy real for the patient. Liquid biopsies isolate and utilize different substrates present in patients' body fluids such as circulating tumor cells, circulating tumor DNA, tumor extracellular vesicles, etc. One of the most-used solid cancers in the development of the non-invasive liquid biopsy approach that has benefited from scientific advances is non-small cell lung cancer (NSCLC). Using liquid biopsy, it is possible to have more details on NSCLC staging, progression, heterogeneity, gene mutations and clonal evolution, etc., basing the treatment on precision medicine as well as on the screening of markers for therapeutic resistance. With this review, the authors propose a complete and current overview of all different liquid biopsies available to date, to understand how much has been carried out and how much remains to be completed for a better characterization of NSCLC.

Real-world outcomes, treatment patterns and T790M testing rates in non-small cell lung cancer patients treated with first-line first- or second-generation epidermal growth factor receptor tyrosine kinase inhibitors from the Slovenian cohort of the REFLECT study

BACKGROUND

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are effective treatments for EGFR mutation-positive (EGFRm) non-small cell lung cancer (NSCLC). However, routine clinical practice is different between countries/institutions.

PATIENTS AND METHODS

The REFLECT study (NCT04031898) is a retrospective medical chart review that explored real-life treatment and outcomes of EGFRm NSCLC patients receiving first-line (1L) first-/second-generation (1G/2G) EGFR TKIs in 8 countries. This study included adult patients with documented advanced/metastatic EGFRm NSCLC with 1L 1G/2G EGFR TKIs initiated between Jan 2015 - Jun 2018. We reviewed data on clinical characteristics, treatments, EGFR/T790M testing patterns, and survival outcomes. Here, we report data from 120 medical charts in 3 study sites from Slovenia.

RESULTS

The Slovenian cohort (median age 70 years, 74% females) received 37% erlotinib, 32% afatinib, 31% gefitinib. At the time of data collection, 94 (78%) discontinuations of 1L TKI, and 89 (74%) progression events on 1L treatment were reported. Among patients progressing on 1L, 73 (82%) were tested for T790M mutation yielding 50 (68%) positive results, and 62 (85%) received 2L treatment. 82% of patients received osimertinib. Attrition rate between 1L and 2L was 10%. The median (95% CI) real-world progression free survival on 1L EGFR TKIs was 15.6 (12.6, 19.2) months; median overall survival (95% CI) was 28.9 (25.0, 34.3) months.

CONCLUSIONS

This real-world study provides valuable information about 1G/2G EGFR TKIs treatment outcomes and attrition rates in Slovenian EGFRm NSCLC patients. The reduced attrition rate and improved survival outcomes emphasize the importance of 1L treatment decision.

Final report on plasma ctDNA T790M monitoring during EGFR-TKI treatment in patients with EGFR mutant non-small cell lung cancer (JP-CLEAR trial)

Osimertinib is active against T790M-positive epidermal growth factor receptor mutant non-small cell lung cancer. We enrolled 122 sensitive epidermal growth factor receptor mutant non-small cell lung cancer patients who were planned to receive or were receiving first-/second-generation epidermal growth factor receptor tyrosine kinase inhibitors without disease progression and monitored plasma T790M every 1-2 months using the cobas® EGFR Mutation Test v2. We previously reported the concordance between T790M status in plasma and tissue. This is the final report on the sensitivity of plasma T790M and the efficacy of sequential osimertinib. The sensitivity was 21.1% (95% confidence interval: 6.1-45.6%). The best overall response was 25.0% (95% confidence interval: 9.8-46.7) in the plasma T790M-positive group and 28.6% (95% confidence interval: 8.4-58.1) in the plasma T790M-negative but tissue T790M-positive group. Median progression-free survival was 7.9 months (95% confidence interval: 4.7-17.5) for the former and 4.4 months (95% confidence interval: 3.0-N.E.) for the latter, with no statistically significant difference (P = 0.74).

Diagnostic and economic value of biomarker testing for targetable mutations in non-small-cell lung cancer: a literature review

We aimed to assess the diagnostic and economic value of next-generation sequencing (NGS) versus single-gene testing, and of liquid biopsy (LBx) versus tissue biopsy (TBx) in non-small-cell lung cancer biomarker testing through literature review. Embase and MEDLINE were searched to identify relevant studies (n = 43) from 2015 to 2020 in adults with advanced non-small-cell lung cancer. For NGS versus single-gene testing, concordance was 70-99% and sensitivity was 86-100%. For LBx versus TBx, specificity was 43-100% and sensitivity was ≥60%. Turnaround times were longer for NGS versus single-gene testing (but not vs sequential testing) and faster for LBx versus TBx. NGS was cost-effective, and LBx reduced US per-patient costs. NGS versus single-gene testing and LBx versus TBx were concordant. NGS and LBx may be cost-effective for initial screening.

Monitoring cfDNA in Plasma and in Other Liquid Biopsies of Advanced EGFR Mutated NSCLC Patients: A Pilot Study and a Review of the Literature

Simple Summary

In advanced non-small cell lung cancer (NSCLC) patients, tumor tissue biopsy represents the gold standard for molecular analysis procedures. However, to achieve the necessary information, both at the time of diagnosis and progressive disease, is sometimes challenging, considering the small cancer material available. Liquid biopsy consists of a non-invasive alternative approach that owns the potential to provide useful information for molecular diagnostic. We aimed to prove the worth of liquid biopsy as plasma but also as urine and exhaled breath condensate (EBC) as the best surrogate to tumor tissue as well as to explore the molecular mechanisms that underlying the resistance to second-line osimertinib in advanced EGFR mutated NSCLC. We believe that our findings, with the PLUREX study and the review of literature, may add another brick in the wall on the use of liquid biopsy in the clinical practice in the setting of EGFR-mutated NSCLC disease.

Abstract

In order to study alternatives at the tissue biopsy to study EGFR status in NSCLC patients, we evaluated three different liquid biopsy platforms (plasma, urine and exhaled breath condensate, EBC). We also reviewed the literature of the cfDNA biological sources other than plasma and compared our results with it about the sensitivity to EGFR mutation determination. Twenty-two EGFR T790M-mutated NSCLC patients in progression to first-line treatment were enrolled and candidate to osimertinib. Plasma, urine and EBC samples were collected at baseline and every two months until progression. Molecular analysis of cfDNA was performed by ddPCR and compared to tissue results. At progression NGS analysis was performed. The EGFR activating mutation detection reached a sensitivity of 58 and 11% and for the T790M mutation of 45 and 10%, in plasma and urine samples, respectively. Any DNA content was recovered from EBC samples. Considering the plasma monitoring study, the worst survival was associated with positive shedding status; both plasma and urine molecular progression anticipated the radiological worsening. Our results confirmed the role of plasma liquid biopsy in testing EGFR mutational status, but unfortunately, did not evidence any improvement from the combination with alternative sources, as urine and EBC.

Serial Plasma Cell-Free Circulating Tumor DNA Tests Identify Genomic Alterations for Early Prediction of Osimertinib Treatment Outcome in EGFR T790M-Positive NSCLC

Introduction

Recent advances in the detection of genomic DNA from plasma samples allow us to follow tumor DNA shedding in plasma during systemic treatment. Osimertinib is the standard of care for patients with NSCLC with acquired EGFR T790M mutations. We assessed changes in serial plasma cell-free circulating tumor DNA (ctDNA) genomic alterations to predict osimertinib efficacy.

Methods

We prospectively collected plasma from patients having EGFR-mutated advanced NSCLC previously treated with EGFR tyrosine kinase inhibitor therapy and with acquired EGFR T790M mutation detected by standard methods. Plasma samples were collected before starting osimertinib treatment, 4 weeks after osimertinib treatment, and on progression. ctDNA was analyzed using the Guardant360 assay.

Results

A total of 15 eligible patients received osimertinib. Before starting treatment, EGFR-activating mutations were detected in the ctDNA of all patients, and EGFR T790M was detected in 93% of the cases. Osimertinib treatment was associated with an objective response rate of 53% and a median progression-free survival of 7.3 months. A total of 12 of the 15 patients had undetectable plasma T790M and decreased activating mutation allelic frequency (AF) at week 4. None of the 12 patients had disease progression within 16 weeks. For the remaining three patients, with detectable plasma T790M (n = 2) or increased activating mutation AF (n = 1) at week 4, two had progressive disease within 16 weeks (p = 0.03).

Conclusions

In patients with EGFR-mutated advanced NSCLC, persistent EGFR T790M or increasing activating mutation AF as detected in ctDNA 4 weeks after the start of osimertinib treatment may predict disease progression within 16 weeks.

A Pan-Canadian Validation Study for the Detection of EGFR T790M Mutation Using Circulating Tumor DNA From Peripheral Blood

INTRODUCTION

Genotyping circulating tumor DNA (ctDNA) is a promising noninvasive clinical tool to identify the EGFR T790M resistance mutation in patients with advanced NSCLC with resistance to EGFR inhibitors. To facilitate standardization and clinical adoption of ctDNA testing across Canada, we developed a 2-phase multicenter study to standardize T790M mutation detection using plasma ctDNA testing.

METHODS

In phase 1, commercial reference standards were distributed to participating clinical laboratories, to use their existing platforms for mutation detection. Baseline performance characteristics were established using known and blinded engineered plasma samples spiked with predetermined concentrations of T790M, L858R, and exon 19 deletion variants. In phase II, peripheral blood collected from local patients with known EGFR activating mutations and progressing on treatment were assayed for the presence of EGFR variants and concordance with a clinically validated test at the reference laboratory.

RESULTS

All laboratories in phase 1 detected the variants at 0.5 % and 5.0 % allele frequencies, with no false positives. In phase 2, the concordance with the reference laboratory for detection of both the primary and resistance mutation was high, with next-generation sequencing and droplet digital polymerase chain reaction exhibiting the best overall concordance. Data also suggested that the ability to detect mutations at clinically relevant limits of detection is generally not platform-specific, but rather impacted by laboratory-specific practices.

CONCLUSIONS

Discrepancies among sending laboratories using the same assay suggest that laboratory-specific practices may impact performance. In addition, a negative or inconclusive ctDNA test should be followed by tumor testing when possible.

Exosomes: a new perspective in EGFR-mutated lung cancer

Exosomes are major contributors in cell to cell communication due to their ability to transfer biological material such as protein, RNA, DNA, and miRNA. Additionally, they play a role in tumor initiation, promotion, and progression, and recently, they have emerged as a potential source of information on tumor detection and may be useful as diagnostic, prognostic, and predictive tools. This review focuses on exosomes from lung cancer with a focus on EGFR mutations. Here, we outline the role of exosomes and their functional effect in carcinogenesis, tumor progression, and metastasis. Finally, we discuss the possibility of exosomes as novel biomarkers in early detection, diagnosis, assessment of prognosis, and prediction of therapeutic response in EGFR-mutated lung cancer.

Impact of detecting plasma EGFR mutations with ultrasensitive liquid biopsy in outcomes of NSCLC patients treated with first- or second-generation EGFR-TKIs

BACKGROUND

Few trials have evaluated the utility of liquid biopsies to detect epidermal growth factor receptor mutations (EGFRm) at the time of response evaluation and its association with the clinical characteristics and outcomes of non-small-cell lung cancer (NSCLC) patients.

OBJECTIVE

This study aimed to evaluate, in a real-world clinical setting, the prevalence of plasma EGFRm and its association with the clinical characteristics, response and survival outcomes of NSCLC patients under treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKIs).

METHODS

This observational study enrolled advanced or metastatic NSCLC patients, with confirmed tumor EGFRm, receiving treatment with first- or second-generation EGFR-TKIs. Blood samples for the detection of plasma EGFRm were collected at the time of response evaluation and processed using the Target Selector™ assay. The main outcomes were the detection rate of plasma EGFRm, median Progression-Free Survival (PFS) and Overall Survival (OS) according to plasma EGFR mutational status.

RESULTS

Of 84 patients, 50 (59.5%) had an EGFRm detected in plasma. After a median follow-up of 21.1 months, 63 patients (75%) had disease progression. The detection rate of plasma EGFRm was significantly higher in patients with disease progression than in patients with partial response or stable disease (68.3% versus 33.3%; P< 0.01). PFS and OS were significantly longer in patients without plasma EGFRm than among patients with plasma EGFRm (14.3 months [95% CI, 9.25-19.39] vs 11.0 months [95% CI, 8.61-13.46]; P= 0.034) and (67.8 months [95% CI, 39.80-95.94] vs 32.0 months [95% CI, 17.12-46.93]; P= 0.006), respectively. A positive finding in LB was associated with the presence of ⩾ 3 more metastatic sites (P= 0.028), elevated serum carcinoembryonic (CEA) at disease progression (P= 0.015), and an increase in CEA with respect to baseline levels (P= 0.038).

CONCLUSIONS

In NSCLC patients receiving EGFR-TKIs, the detection of plasma EGFRm at the time of tumor response evaluation is associated with poor clinical outcomes.

Sputum cell-free DNA: Valued surrogate sample for the detection of EGFR exon 20 p.T790M mutation in patients with advanced lung adenocarcinoma and acquired resistance to EGFR-TKIs

BACKGROUND

Sputum cell-free DNA (cfDNA) is a valuable surrogate sample for assessing EGFR-sensitizing mutations in patients with advanced lung adenocarcinoma. Detecting EGFR exon 20 p.T790 M (p.T790 M) is much more challenging due to its limited availability in tumor tissues. Exploring sputum cfDNA as an alternative for liquid-based sample type in detecting p.T790 M requires potential improvement in clinical practice.

METHODS

A total of 34 patients with EGFR-sensitive mutation-positive lung adenocarcinoma and acquired resistance to the first generation of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) were enrolled. The sputum samples, and paired tumors and/or plasma samples were tested for p.T790 M mutation and concordance of p.T790 M status among the three sample types was analyzed.

RESULTS

The overall concordance rate of p.T790 M mutation between sputum cfDNA and tumor tissue samples was 85.7%, with a sensitivity of 66.7% and a specificity of 100%. The sensitivity for detecting p.T790 M in sputum cfDNA was 100%, 66.7%, and 0% in the three sputum groups of malignant, satisfactory but no malignant cells, and unsatisfactory, respectively. The combined results of plasma cfDNA testing and sputum cfDNA testing further increased the sensitivity to 100% for p.T790 M detection in satisfactory but no malignant cells sputum group.

CONCLUSION

These findings revealed that cfDNA from malignant or satisfied but no malignant cells sputum is considered suitable for detecting p.T790 M mutation in patients with acquired resistance to first or second-generation EGFR-TKIs. The sputum cytological pathological evaluation-guided sputum cfDNA testing assists in significantly improving the sensitivity of p.T790 M detection, bringing significant value for the maximal application of third-generation EGFR-TKIs in second-line treatment.

EGFR tyrosine kinase inhibitors for EGFR mutation-positive non-small-cell lung cancer: outcomes in Asian populations

Few data are available that have compared outcomes with different EGFR tyrosine kinase inhibitors (TKIs) specifically in Asian patients with EGFR mutation-positive non-small-cell lung cancer. In this narrative review, we have collated available data from prospective studies that have assessed first-, second- and third-generation EGFR TKIs in Asian populations, including subanalyses in individual countries (China and Japan). These data indicate that outcomes with first- and second-generation TKIs are broadly similar in Asian and non-Asian populations. However, while the third-generation EGFR TKI, osimertinib, confers significant overall survival benefit over erlotinib/gefitinib in non-Asians, this is not apparent in Asians, particularly in countries like Japan with well-resourced healthcare. Head-to-head comparisons of second- and third-generation EGFR TKIs, with OS as a primary end point, should be considered in Asia.

Detection of EGFR Mutations in Plasma Cell-Free Tumor DNA of TKI-Treated Advanced-NSCLC Patients by Three Methodologies: Scorpion-ARMS, PNAClamp, and Digital PCR

Analysis of circulating cell-free tumor DNA (cftDNA) has emerged as a specific and sensitive blood-based approach to detect epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) patients. Still, there is some debate on what should be the preferential clinical method for plasma-derived cftDNA analysis. We tested 31 NSCLC patients treated with anti-EGFR tyrosine kinase inhibitors (TKIs), at baseline and serially during therapy, by comparing three methodologies in detecting EGFR mutations (L858R, exon 19 deletion, and T790M) from plasma: scorpions-amplification refractory mutation system (ARMS) methodology by using EGFR Plasma RGQ PCR Kit-QIAGEN, peptide nucleic acid (PNA) clamp and PANA RealTyper integration by using PNAClamp EGFR-PANAGENE, and digital real time PCR by using QuantStudio 3D Digital PCR System-Thermo Fisher Scientific. Specificity was 100% for all three mutations, independently from the platform used. The sensitivity for L858R (42.86%) and T790M (100%) did not change based on the method, while the sensitivity for Del 19 differed markedly (Scorpion-ARMS 45%, PNAClamp 75%, and Digital PCR 85%). The detection rate was also higher (94.23%) as measured by Digital PCR, and when we monitored the evolution of EGFR mutations over time, it evidenced the extreme inter-patient heterogeneity in terms of levels of circulating mutated copies. In our study, Digital PCR showed the best correlation with tissue biopsy and the highest sensitivity to attain the potential clinical utility of monitoring plasma levels of EGFR mutations.

The next tier of EGFR resistance mutations in lung cancer

EGFR mutations account for the majority of druggable targets in lung adenocarcinoma. Over the past decades the optimization of EGFR inhibitors revolutionized the treatment options for patients suffering from this disease. The pace of this development was largely dictated by the inevitable emergence of resistance mutations during drug treatment. As a result, a rapid understanding of the structural and molecular biology of the individual mutations is the key for the development of next-generation inhibitors. Currently, the field faces an unprecedented number of combinations of activating mutations with distinct resistance mutations in parallel to the approval of osimertinib as a first-line drug for EGFR-mutant lung cancer. In this review, we present a survey of the diverse landscape of EGFR resistance mechanisms with a focus on new insights into on-target EGFR kinase mutations. We discuss array of mutations, their structural effects on the EGFR kinase domain as well as the most promising strategies to overcome the individual resistance profiles found in lung cancer patients.

A Multi-Center, Real-Life Experience on Liquid Biopsy Practice for EGFR Testing in Non-Small Cell Lung Cancer (NSCLC) Patients

Background: circulating tumor DNA (ctDNA) is a source of tumor genetic material for EGFR testing in NSCLC. Real-word data about liquid biopsy (LB) clinical practice are lacking. The aim of the study was to describe the LB practice for EGFR detection in North Eastern Italy. Methods: we conducted a multi-regional survey on ctDNA testing practices in lung cancer patients. Results: Median time from blood collection to plasma separation was 50 min (20–120 min), median time from plasma extraction to ctDNA analysis was 24 h (30 min–5 days) and median turnaround time was 24 h (6 h–5 days). Four hundred and seventy five patients and 654 samples were tested. One hundred and ninety-two patients were tested at diagnosis, with 16% EGFR mutation rate. Among the 283 patients tested at disease progression, 35% were T790M+. Main differences in LB results between 2017 and 2018 were the number of LBs performed for each patient at disease progression (2.88 vs. 1.2, respectively) and the percentage of T790M+ patients (61% vs. 26%).