Re-biopsy and liquid biopsy for patients with non-small cell lung cancer after EGFR-tyrosine kinase inhibitor failure

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.

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.

The Feasibility of Interventional Pulmonology Methods for Detecting the T790M Mutation after the First or Second-Generation EGFR-TKI Resistance of Non-Small Cell Lung Cancer

The development of third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) targeting T790M-mutant non-small cell lung cancer (NSCLC) has raised the importance of re-biopsy after EGFR-TKI failure. This study aimed to investigate the feasibility of interventional pulmonology (IP) procedures as re-biopsy methods for identifying the T790M mutation in EGFR-TKI-resistant patients. One hundred and thirty-nine NSCLC patients who underwent IP procedures for re-biopsy as their initial investigation after EGFR-TKI treatment failure were enrolled in this study between January 2020 and August 2022. All patients underwent a first re-biopsy with IP methods, with a diagnostic yield of 81.2% and T790M mutation detection rate of 36%. Thirty patients underwent a second re-biopsy; IP methods were used for 17 (56.6%) patients and non-IP methods for 13 (43.4%) patients; the T790M mutation detection rate was 36.4%. Only six patients underwent a third re-biopsy; no T790M mutation was noted. The T790M mutation detection rate did not differ between IP and non-IP methods (33.6 % vs. 37.5%, p = 0.762). In 11 cases (7.5%), a re-biopsy revealed histologic transformation from lung adenocarcinoma. IP procedures, as first-line re-biopsy methods for NSCLC, are feasible and provide sufficient tissue for identification of the resistance mechanism and target gene T790M mutation.

Dual NGS Comparative Analysis of Liquid Biopsy (LB) and Formalin-Fixed Paraffin-Embedded (FFPE) Samples of Non-Small Cell Lung Carcinoma (NSCLC)

Lung cancer ranks second worldwide after breast cancer and third in Europe after breast and colorectal cancers when both sexes and all ages are considered. In this context, the aim of this study was to emphasize the power of dual analysis of the molecular profile both in tumor tissue and plasma by NGS assay as a liquid biopsy approach with impact on prognosis and therapy modulation in NSCLC patients. NGS analysis was performed both from tissue biopsies and from cfNAs isolated from peripheral blood samples. Out of all 29 different mutations detectable by both NGS panels (plasma and tumor tissue), seven different variants (24.13%; EGFR L858R in two patients, KRAS G13D and Q61H and TP53 G244D, V197M, R213P, and R273H) were detected only in plasma and not in the tumor itself. These mutations were detected in seven different patients, two of them having known distant organ metastasis. Our data show that NGS analysis of cfDNA could identify actionable mutations in advanced NSCLC and, therefore, this analysis could be used to monitor the disease progression and the treatment response and even to modulate the therapy in real time.

T790M mutation positive squamous cell carcinoma transformation from EGFR-mutated lung adenocarcinoma after low dose erlotinib: A case report and literature review

RATIONALE

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are widely used for the treatment of EGFR mutation positive advanced nonsmall cell lung cancer (NSCLC); however, acquired resistance is known to develop during these treatments. Among these mechanisms, histological transformation is seldom encountered. Although platinum based chemotherapy has been reported to be effective in the treatment of patients with small cell lung cancer transformation, there is a lack of information on the treatment of patients with squamous cell carcinoma (SQ) transformation.

PATIENT CONCERNS AND DIAGNOSIS

An 80-year-old nonsmoking woman was referred to our hospital because of an abnormal shadow on her chest radiograph. Diagnostic bronchoscopy was performed and pathological examination revealed adenocarcinoma. Mutation analysis of the EGFR gene revealed deletion of E746-A750 in exon 19. She refused both surgical treatment and radiation therapy, and preferred periodic radiologic follow-up. Unfortunately, approximately a year and a half after the initial diagnosis, the primary lesion enlarged, and many pleural nodules were newly detected (clinically T4N2M1a, stage IVA).

INTERVENTIONS AND OUTCOMES

Based on EGFR mutation analysis, a reduced dose of daily erlotinib was prescribed, which achieved a partial response and 34 months of progression-free survival (PFS). A repeated biopsy with an endobronchial cryoprobe was performed on the enlarged primary lesion. Pathological examination revealed SQ harboring an identical EGFR mutation with a secondary EGFR T790M mutation. Osimertinib 80 mg once a day was started as second line therapy, which resulted in 8 months of PFS and 15 months of survival.

LESSON

The literature review and our report suggest that osimertinib is a promising treatment for NSCLC regardless of histology if T790M is present as an acquired mutation.

Efficacy of Osimertinib in EGFR-Mutated Advanced Non-small-Cell Lung Cancer With Different T790M Status Following Resistance to Prior EGFR-TKIs: A Systematic Review and Meta-analysis

Purpose

Epidermal growth factor receptor (EGFR) T790M-negative/unknown advanced non-small cell lung cancer (NSCLC) patients lack subsequent approved targeted therapies. This meta-analysis aimed to assess the efficacy of osimertinib in advanced NSCLC patients with different T790M status after resistance to prior first- or second-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs) and to predict the subgroups that may benefit beside T790M-positive disease.

Methods

PubMed, Embase, Web of Science, and Cochrane Library databases were searched for relevant trials. Meeting abstracts were also reviewed to identify appropriate studies. Studies evaluating the efficacy and/or survival outcomes of osimertinib in patients with different T790M status (positive, negative, or unknown) after resistance to prior first- or second-generation EGFR-TKIs were enrolled, and data were pooled to assess hazard ratios (HRs) or relative risk ratios (RRs) in terms of overall survival (OS), progression-free survival (PFS), and objective response rate (ORR).

Results

A total of 1,313 EGFR-mutated NSCLC patients from 10 retrospective and one prospective studies treated with osimertinib after resistance to first- or second-generation EGFR-TKIs were included. In overall groups, T790M-positive patients showed an improved OS (HR=0.574, p=0.015), PFS (HR = 0.476, p = 0.017), and ORR (RR = 2.025, p = 0.000) compared with T790M-negative patients. In the brain metastases subgroup, no significant difference in OS was observed between T790M-positive and T790M-negative patients (HR = 0.75, p = 0.449) or between T790M-positive and T790M-unknown patients (HR = 0.90, p = 0.673). In the plasma genotyping subgroup, PFS was similar between T790M-positive and T790M-negative patients (HR = 1.033, p = 0.959).

Conclusion

Patients with progressive brain metastases on first- or second-generation EGFR-TKIs can benefit from subsequent osimertinib therapy regardless of T790M status. Patients with plasma T790M-negative status and lack of tissue genotyping should be allowed to receive osimertinib treatment.

Observational study of rebiopsy in EGFR-TKI-resistant patients with EGFR mutation-positive advanced NSCLC

The identification of acquired resistance mutations has been essential in non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) active mutations. Rebiopsy plays a pivotal role in selecting the optimal treatment for patients who develop resistance to initial EGFR-tyrosine kinase inhibitors (EGFR-TKIs). This multicenter, observational study was conducted to investigate the details of rebiopsy in Japanese clinical practice. The primary endpoints were the implementation rate of rebiopsy and the concordance rate for T790M mutation detection between histological and cytological specimens using the cobas EGFR Mutation Test, version 2. One hundred ninety-four patients with EGFR-mutant NSCLC were enrolled, and 120 patients developed acquired resistance to EGFR-TKIs. The median age was 68 years (range 20-87), and 52.5% of the patients were women. Rebiopsy was performed in 109 patients, and the implementation rate of rebiopsy was 90.8%. The success rates of rebiopsy in the total, histology, cytology and liquid biopsy populations were 67.9%, 81.3%, 66.7% and 43.8%, respectively. The positive percent agreement and the negative percent agreement in the detection of the T790M mutation between the histological and cytological specimens were both 90.9%. Obtaining histological or cytological tissue samples at rebiopsy may contribute to improving the detection rate of the T790M mutation (trial registration number: UMIN000026019).

Serum NSE is Early Marker of Transformed Neuroendocrine Tumor After EGFR-TKI Treatment of Lung Adenocarcinoma

Background

Transformation to a lung neuroendocrine tumor (LNET) is a mechanism of resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI). Serum neuron-specific enolase (NSE) is a useful marker in the detection of LNET. Therefore, we explored the clinical significance of serum NSE levels in the detection of transformed neuroendocrine tumors after EGFR-TKI therapy.

Methods

We report a cohort of 5 cases in our treatment group. The characteristics of the patients, pathological diagnoses, immunohistochemistry with molecular detection, laboratory examination, and treatment histories are analyzed. The tumor markers of serum NSE were analyzed. Additionally, we reviewed the publications reporting the tumor markers before and after LNET transformation during EGFR-TKI therapy.

Results

Most patients are female (3/5), aged <60 years old (4/5), nonsmokers (4/5) and harbor the EGFR 19 exon deletion (4/5). The median time of LNET transformation was 19 months (range: 12–31 months). The clinical characteristics were similar to those reported in previous studies. Laboratory examination revealed an increased NSE level before the LNET is defined. Sixteen publications were reviewed. Of those, 86.67% (13/15) publications showed an increased level of NSE when the LNET transformation was defined.

Conclusion

Adenocarcinoma tumors in non-smokers, young patients harboring the EGFR 19 exon deletion tended to transform to LNETs after EGFR-TKI therapy. Combining our findings and a review of the literature, we suggest that serum NSE may be a useful tumor marker to predict neuroendocrine tumor transformation.

Integration of liquid biopsy and pharmacogenomics for precision therapy of EGFR mutant and resistant lung cancers

The advent of molecular profiling has revolutionized the treatment of lung cancer by comprehensively delineating the genomic landscape of the epidermal growth factor receptor (EGFR) gene. Drug resistance caused by EGFR mutations and genetic polymorphisms of drug metabolizing enzymes and transporters impedes effective treatment of EGFR mutant and resistant lung cancer. This review appraises current literature, opportunities, and challenges associated with liquid biopsy and pharmacogenomic (PGx) testing as precision therapy tools in the management of EGFR mutant and resistant lung cancers. Liquid biopsy could play a potential role in selection of precise tyrosine kinase inhibitor (TKI) therapies during different phases of lung cancer treatment. This selection will be based on the driver EGFR mutational status, as well as monitoring the development of potential EGFR mutations arising during or after TKIs treatment, since some of these new mutations may be druggable targets for alternative TKIs. Several studies have identified the utility of liquid biopsy in the identification of EGFR driver and acquired resistance with good sensitivities for various blood-based biomarkers. With a plethora of sequencing technologies and platforms available currently, further evaluations using randomized controlled trials (RCTs) in multicentric, multiethnic and larger patient cohorts could enable optimization of liquid-based assays for the detection of EGFR mutations, and support testing of CYP450 enzymes and drug transporter polymorphisms to guide precise dosing of EGFR TKIs.

Adequacy of samples obtained via percutaneous core-needle rebiopsy for EGFR T790M molecular analysis in patients with non-small cell lung cancer following acquired resistance to first-line therapy: A systematic review and meta-analysis

MICRO ABSTRACT

Rebiopsies characterizing resistance mutations in patients with non-small cell lung cancer (NSCLC) can guide personalized medicine and improve overall survival rates. In this systematic review, we examine the suitability of percutaneous core-needle biopsy (PT-CNB) to obtain adequate samples for molecular characterization of the acquired resistance mutation T790M. This review provides evidence that PT-CNB can obtain samples with high adequacy, with a mutation detection rate that is in accordance with prior literature.

BACKGROUND

Non-small cell lung cancer (NSCLC) comprises 85% of all lung cancers and has seen improved survival rates with the rise of personalized medicine. Resistance mutations to first-line therapies, such as T790M, however, render first-line therapies ineffective. Rebiopsies characterizing resistance mutations inform therapeutic decisions, which result in prolonged survival. Given the high efficacy of percutaneous core-needle biopsy (PT-CNB), we conducted the first systematic review to analyze the ability of PT-CNB to obtain samples of high adequacy in order to characterize the acquired resistance mutation T790M in patients with NSCLC.

METHODS

We performed a comprehensive literature search across PubMed, Embase, and CENTRAL. Search terms related to "NSCLC," "rebiopsy," and "PT-CNB" were used to obtain results. We included all prospective and retrospective studies that satisfied our inclusion and exclusion criteria. A random effects model was utilized to pool adequacy and detection rates of the chosen articles. We performed a systematic review, meta-analysis, and meta-regression to investigate the adequacy and T790M detection rates of samples obtained via PT-CNB.

RESULTS

Out of the 173 studies initially identified, 5 studies met the inclusion and exclusion criteria and were chosen for our final cohort of 436 patients for meta-analysis. The pooled adequacy rate of samples obtained via PT-CNB was 86.92% (95% CI: [79.31%, 92.0%]) and the pooled T790M detection rate was 46.0% (95% CI: [26.6%, 66.7%]). There was considerable heterogeneity among studies (I² > 50%) in both adequacy and T790M detection rates.

CONCLUSION

PT-CNB can obtain adequate samples for T790M molecular characterization in NSCLC lung cancer patients. Additional prospective studies are needed to corroborate the results in this review.

Tissue Adequacy and Safety of Percutaneous Transthoracic Needle Biopsy for Molecular Analysis in Non-Small Cell Lung Cancer: A Systematic Review and Meta-analysis

Objective

We conducted a systematic review and meta-analysis of the tissue adequacy and complication rates of percutaneous transthoracic needle biopsy (PTNB) for molecular analysis in patients with non-small cell lung cancer (NSCLC).

Materials and Methods

We performed a literature search of the OVID-MEDLINE and Embase databases to identify original studies on the tissue adequacy and complication rates of PTNB for molecular analysis in patients with NSCLC published between January 2005 and January 2020. Inverse variance and random-effects models were used to evaluate and acquire meta-analytic estimates of the outcomes. To explore heterogeneity across the studies, univariable and multivariable meta-regression analyses were performed.

Results

A total of 21 studies with 2232 biopsies (initial biopsy, 8 studies; rebiopsy after therapy, 13 studies) were included. The pooled rates of tissue adequacy and complications were 89.3% (95% confidence interval [CI]: 85.6%–92.6%; I² = 0.81) and 17.3% (95% CI: 12.1%–23.1%; I² = 0.89), respectively. These rates were 93.5% and 22.2% for the initial biopsies and 86.2% and 16.8% for the rebiopsies, respectively. Severe complications, including pneumothorax requiring chest tube placement and massive hemoptysis, occurred in 0.7% of the cases (95% CI: 0%–2.2%; I² = 0.67). Multivariable meta-regression analysis showed that the tissue adequacy rate was not significantly lower in studies on rebiopsies (p = 0.058). The complication rate was significantly higher in studies that preferentially included older adults (p = 0.001).

Conclusion

PTNB demonstrated an average tissue adequacy rate of 89.3% for molecular analysis in patients with NSCLC, with a complication rate of 17.3%. PTNB is a generally safe and effective diagnostic procedure for obtaining tissue samples for molecular analysis in NSCLC. Rebiopsy may be performed actively with an acceptable risk of complications if clinically required.

Resistance Profile of Osimertinib in Pre-treated Patients With EGFR T790M-Mutated Non-small Cell Lung Cancer

Background: Osimertinib efficacy in pre-treated patients with epidermal growth factor receptor (EGFR) T790M-mutated non-small cell lung cancer (NSCLC) has been demonstrated in clinical trials, but real-world data, particularly regarding resistance profile, remains limited. This study aims to analyze the resistance mechanisms acquired after treatment with Osimertinib.

Methods: Clinical outcomes and molecular results from re-biopsies at the time of osimertinib progression of EGFR T790M-mutated NSCLC patient were analyzed.

Results: Twenty-one patients with stage IV adenocarcinoma were included [median 69 years; 57.1% female; 85.7% never-smokers; 23.8% ECOG performance status (PS) ≥2]. Median PFS and OS were 13.4 (95% CI: 8.0–18.9) and 26.4 (95% IC: 8.9–43.8) months, respectively. At the time of analysis, 10 patients had tumor progression (47.6%). T790M loss occurred in 50%, being associated with earlier progression (median PFS 8.1 vs. 21.4 months, p = 0.011). Diverse molecular alterations were identified, including C797S mutation (n = 1), PIK3CA mutation (n = 2), MET amplification (n = 1), CTNNB1 mutation (n = 1), and DCTN1-ALK fusion (n = 1). Histological transformation into small cell carcinoma occurred in one patient.

Conclusions: This real-world life study highlights the relevance of re-biopsy at the time of disease progression, contributing to understand resistance mechanisms and to guide treatment strategies.

Next-Generation Sequencing with Liquid Biopsies from Treatment-Naïve Non-Small Cell Lung Carcinoma Patients

Recently, the liquid biopsy (LB), a non-invasive and easy to repeat approach, has started to compete with the tissue biopsy (TB) for detection of targets for administration of therapeutic strategies for patients with advanced stages of lung cancer at tumor progression. A LB at diagnosis of late stage non-small cell lung carcinoma (NSCLC) is also being performed. It may be asked if a LB can be complementary (according to the clinical presentation or systematics) or even an alternative to a TB for treatment-naïve advanced NSCLC patients. Nucleic acid analysis with a TB by next-generation sequencing (NGS) is gradually replacing targeted sequencing methods for assessment of genomic alterations in lung cancer patients with tumor progression, but also at baseline. However, LB is still not often used in daily practice for NGS. This review addresses different aspects relating to the use of LB for NGS at diagnosis in advanced NSCLC, including its advantages and limitations.

Re-biopsy after first line treatment in advanced NSCLC can reveal changes in PD-L1 expression

OBJECTIVES

Re-biopsy in progressive advanced Non-Small-Cell Lung Cancer (NSCLC) after first line treatment may reveal information about evolving tumor biology during treatment. Our study aims to investigate the feasibility, risk of complications, and clinical relevance of performing re-biopsy systematically.

MATERIALS AND METHODS

NSCLC patients with advanced, non-targetable disease, receiving first line systemic treatment, were included in a prospective single-centre study (NCT03512847). A diagnostic biopsy was performed at baseline and repeated at time of progression, preferentially from the progressive lesions as determined by CT or PET/CT. The primary endpoint was feasibility, including complication rate to re-biopsy. Secondary endpoints were clinical relevance, defined as a potential of changing treatment or follow-up, due to new histological evidence, specifically a change in PD-L1 Tumor Proportion Score (TPS).

RESULTS

Fifty-one patients with progressive advanced NSCLC had re-biopsy performed. Median time from patients' acceptance to biopsy was seven days (range: 0-31). Complication rate was 6% (n = 3) represented by pneumothorax, hydro-pneumothorax and pneumonia, respectively. No severe or chronic complications occurred. Sufficient material for PD-L1 analyses was obtained in 46 of 51 patients: the remaining five cases had insufficient tissue for analyses, no malignant cells/only suspected malignant cells, questioning whether progression was real. PD-L1 TPS change was observed in 33% of patients (n = 15) and 17% (n = 8) had potentially clinically relevant changes. A significantly higher chance of PD-L1 TPS change was observed in chemotherapy-treated patients.

CONCLUSION

Our study showed that re-biopsy is feasible, with low risk of complications, and can be clinically relevant in patients with suspected progression in advanced NSCLC.

An EGFR T790M-mutated lung adenocarcinoma undergoing large-cell neuroendocrine carcinoma transformation after osimertinib therapy: a case report

BACKGROUND

Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor, is selective for both epidermal growth factor receptor tyrosine kinase inhibitor-sensitizing and T790M resistance mutations. Almost all patients who initially respond to an epidermal growth factor receptor tyrosine kinase inhibitor subsequently report disease progression. Epidermal growth factor receptor-dependent resistance mechanisms, bypass pathway activation, and histological transformation have been reported with osimertinib therapy.

CASE PRESENTATION

We report a case of a 64-year-old Asian man with epidermal growth factor receptor T790M-positive adenocarcinoma that transformed to epidermal growth factor receptor T790M-negative large-cell neuroendocrine carcinoma after osimertinib therapy. A prompt rebiopsy revealed a rare mechanism of resistance to epidermal growth factor receptor tyrosine kinase inhibitor, and subsequently treatment with carboplatin and etoposide was effective.

CONCLUSIONS

Despite the promising emergence of circulating tumoral DNA testing, this case report emphasizes the importance of rebiopsy of a progressive epidermal growth factor receptor-mutant tumor.

[Advances of Exosomes Extraction and Its Mechanism in Early Diagnosis of Lung Cancer]

肺癌是世界范围内发病率和死亡率较高的恶性肿瘤之一，严重威胁着国民的生命安全与健康。肺癌的早期诊断是肺癌预防和治疗过程中的关键环节，对肺癌进行早期诊断有利于提高患者的生存率。外泌体(exosomes)与肿瘤的侵袭与转移过程密切相关，在肺癌的发生发展过程中，外泌体发挥着重要的调控作用。近年来，以外泌体为载体的生物标记物成为肺癌强有力的诊断工具。外泌体是一种由细胞分泌的由膜包裹的大小均一、直径约为30 nm-200 nm的脂质双分子层结构小囊泡。外泌体的内容物包含不同类型的核酸和蛋白质，这些核酸和蛋白质来源于其亲本细胞(包括亲本癌细胞)，具有广泛的生理功能，包括参与免疫调节、细胞间联络等。外泌体中的生物大分子物质，如单链RNA、长非编码RNA、微小RNA(microRNA, miRNA)、蛋白质以及脂类，可以为肺癌的早期临床诊断提供有价值的信息。因此，本文就外泌体的来源、结构特点、提取方法、生物学特性和在肺癌早期诊断中的作用研究进展做简要阐述。

Real-world osimertinib for EGFR mutation-positive non-small-cell lung cancer with acquired T790M mutation

Aim: Osimertinib is a key drug for EGFR mutation-positive non-small-cell lung cancer (NSCLC). As the hazards ratio of overall survival in comparison with first-generation EGFR-tyrosine kinase inhibitors was almost similar between FLAURA and ARCHER 1050, salvage use of osimertinib is still a treatment option. Patients & methods: We retrospectively analyzed the clinical courses of EGFR mutation-positive NSCLC patients who were potential candidates for salvage osimertinib. Results: Among 524 patients enrolled from five hospitals, 302 patients underwent biopsy, with 52.6% detection rate of T790M. Osimertinib was administered in 93.6% of the T790M-positive patients. The overall response rate and median progression-free survival time of osimertinib were calculated with 147 patients, to be 55.6% and 17.2 months, respectively. Conclusion: Osimertinib is active for T790M-driven acquired resistance in EGFR-mutant NSCLC, but the detection of T790M was unsatisfactory. Clinical Trial Registration: UMIN000028989 (UMIN Clinical Trials Registry).