Monitoring EGFR T790M with plasma DNA from lung cancer patients in a prospective observational study
Naoko Sueoka‐AraganeNobuyuki KatakamiMiyako SatouchiSoichiro YokotaKeisuke AoeKentaro IwanagaKojiro OtsukaSatoshi MoritaShinya KimuraShunichi Negoro
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Use of plasma DNA to detect mutations has spread widely as a form of liquid biopsy. EGFR T790M has been observed in half of lung cancer patients who have acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKI). Effectiveness of monitoring T790M via plasma DNA during treatment with EGFR-TKI has not been established as an alternative to re-biopsy. This was a prospective multicenter observational study involving non-small cell lung cancer patients carrying EGFR L858R or exon 19 deletions, treated with EGFR-TKI. The primary objective was to determine whether T790M could be detected using plasma DNA in patients with progressive disease (PD). T790M was examined using the mutation-biased PCR and quenching probe (MBP-QP) method, a sensitive, fully-automated system developed in our laboratory. Eighty-nine non-small cell lung cancer patients were enrolled from seven hospitals in Japan. Sequential examinations revealed T790M in plasma DNA among 40% of patients who developed PD. Activating mutations, such as L858R and exon 19 deletions, were detected in 40% of patients using plasma DNA, and either T790M or activating mutations were observed in 62%. Dividing into four periods (before PD, at PD, at discontinuation of EGFR-TKI and subsequently), T790M was detected in 10, 19, 24 and 27% of patients, respectively. Smokers, males, patients having exon 19 deletions and patients who developed new lesions evidenced significantly frequent presence of T790M in plasma DNA. Monitoring T790M with plasma DNA using MBP-QP reflects the clinical course of lung cancer patients treated with EGFR-TKI. Detection of T790M with plasma DNA was correlated with EGFR mutation type, exon 19 deletions and tumor progression. Re-biopsy could be performed only in 14% of PD cases, suggesting difficulty in obtaining re-biopsy specimens in practice. Monitoring T790M with plasma DNA reflects the clinical course, and is potentially useful in designing strategies for subsequent treatment.Keywords:
T790M
Liquid biopsy
Although gefitinib is known to possess an effect inducing apoptosis against lung cancer, it is not clear how clinically effective it is in this regard in patients with lung cancer. Therefore, we tried to reduce its administration from every to every other day in a 73-year-old woman in good condition over 5 years after the recurrence of lung cancer. As a result, her CEA serum level then commenced to increase to the abnormal range within a month. Apoptosis induced by gefitinib was thought not sufficient to kill all lung cancer cells even though well controlled by it for a long period.
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背景．Gefitinib投与前に活性型EGFR遺伝子とEGFR-TKI耐性遺伝子変異（T790M）を同時に認める症例は稀である．当院では，2008年からの3年間で非小細胞肺癌503例中146例に活性型EGFR遺伝子変異を認め，そのうち3例にT790Mを同時に認めた．症例．症例1．70歳，男性．腺癌，cT2aN2M1b（OSS・BRA）stage IV，L858RとT790Mを検出．二次治療としてGefitinibを投与されるも原発巣の増大を認め中止．症例2．81歳，男性．腺癌で右下葉切除術（pT1N0M0）．その後，多発肺転移で再発．L858RとG719S，T790Mを検出．Gefitinibによる治療でPR判定．症例3．80歳，男性．腺癌，cT2bN3M0，stage IIIB，エクソン19欠失変異とT790Mを検出．根治的胸部放射線治療後，原発巣の再増大と肺転移を認め，Gefitinibによる治療でPR判定．結論．治療前にT790Mと活性型遺伝子変異が同時に発現している症例は少数ながら存在し，発現機序は明らかではないが，一部にEGFR-TKIの効果がみられる症例もある．
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EGFR is frequently mutated and amplified in lung adenocarcinomas sensitive to EGFR inhibitors gefitinib and erlotinib. A secondary mutation, T790M, has been associated with acquired resistance but has not been shown to be sufficient to render EGFR mutant/amplified lung cancers resistant to EGFR inhibitors. We created a model for studying acquired resistance to gefitinib by prolonged exposure of a gefitinib-sensitive lung carcinoma cell line (H3255; EGFR mutated and amplified) to gefitinib in vitro. The resulting resistant cell line acquired a T790M mutation in a small fraction of the amplified alleles that was undetected by direct sequencing and identified only by a highly sensitive HPLC-based technique. In gefitinib-sensitive lung cancer cells with EGFR mutations and amplifications, exogenous introduction of EGFR T790M effectively conferred resistance to gefitinib and continued ErbB-3/PI3K/Akt signaling when in cis to an activating mutation. Moreover, continued activation of PI3K signaling by the PIK3CA oncogenic mutant, p110alpha E545K, was sufficient to abrogate gefitinib-induced apoptosis. These findings suggest that allelic dilution of biologically significant resistance mutations may go undetected by direct sequencing in cancers with amplified oncogenes and that restoration of PI3K activation via either a T790M mutation or other mechanisms can provide resistance to gefitinib.
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Non-small-cell lung cancers with epidermal growth factor receptor (EGFR) mutations are sensitive to EGFR tyrosine kinase inhibitors (TKIs); however, unlike cytotoxic agents, it is generally accepted that minimal doses of drugs inhibiting target molecules are sufficient when molecular-targeted agents, including EGFR-TKIs, are used. Thus, any utility of higher doses remains unclear. We compared low-dose (15 mg/kg) gefitinib therapy with high-dose (50 mg/kg) therapy using an EGFR-mutated lung cancer xenograft model. Both gefitinib doses induced tumor shrinkage, but tumors regrew in the low-dose group within 1 month, whereas tumors in the high-dose group did not. Neither the T790M mutation nor MET amplification was apparent in regrown tumors. We also compared outcomes after two doses of gefitinib (5 and 25 mg/kg) in a transgenic EGFR-mutated lung cancer mouse model. In line with the results obtained using the xenograft model, both gefitinib doses completely inhibited tumor growth, but tumors treated with the lower dose of gefitinib developed earlier drug resistance. In conclusion, a low gefitinib dose caused tumors to become drug-resistant prior to acquisition of the T790M mutation or MET amplification in EGFR-mutated models of lung cancer. This suggests that it is important to optimize the EGFR-TKI dose for treatment of EGFR mutation-associated lung cancer. Gefitinib may need to be given at a dose greater than the minimum required for inhibition of target molecules.
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Although patients with non‑small cell lung cancer (NSCLC) experience an initial response to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib, those individuals with activating mutations in EGFR develop resistance. Gambogic acid (GA), a polyprenylated xanthone, has strong antitumor activities. In the present study, the therapeutic efficacy of gefitinib with GA was evaluated in a gefitinib‑resistant NSCLC model. The NCI‑H1975 cell line with EGFR‑T790M mutation was subcutaneously injected into immunocompromised mice. The mice were randomly assigned to receive treatment with gefitinib, GA, gefitinib plus GA, or vehicle for 4 weeks, then all mice were sacrificed and their tumor tissues were subjected to caspase activity detection and western blot analysis. Gefitinib and GA alone slightly inhibited the tumor growth of NCI‑H1975. However, the combined treatment significantly enhanced their antitumor effects, without any marked adverse events. In addition, gefitinib plus GA enhanced the level of apoptosis in the tumor tissues. Western blot analysis also revealed that the combination treatment reduced the phosphorylation level of AKT, MEK1/2 and ERK1/2, while an increased expression ratio of Bax/Bcl‑2 was observed. In the current study, gefitinib in combination with GA resulted in antitumor growth in the EGFR‑T790M secondary mutation NCI‑H1975 tumor model due to an enhanced apoptotic effect. This novel therapeutic strategy may be a practical approach for the treatment of patients who show gefitinib resistance.
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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.A ddPCR assay was optimized to detect the EGFR T790M mutation in plasma samples from 77 patients with NSCLC in progression.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.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.
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Background: The detection of the EGFR T790M (T790M) mutation in non-small cell lung cancer (NSCLC) patients who progressed under treatment with first- or second-generation EGFR-tyrosine kinase inhibitors (TKIs) is important to offer a subsequent therapy with a third-generation EGFR-TKI. Liquid biopsy is a powerful tool to determine the T790M mutation status. Several liquid biopsy platforms with varying degrees of accuracy are available to test for T790M mutations and sensitivities may differ among these methods. Methods: As no standard exists for the testing of T790M mutation in liquid biopsy, we performed a collaborative study to describe and compare the sensitivity of different in-house liquid biopsy platforms for the detection of the T790M mutation, EGFR exon 19 deletion (del19) and EGFR L858R mutation (L858R) across multiple participating laboratories in seven Central and Eastern European countries. Results: Of the 25 invited laboratories across Central and Eastern Europe, 21 centers participated and received 10 plasma samples spiked with cell-line DNA containing the T790M, del19, or L858R mutation in different concentrations. In-house PCR-based and NGS-based methods were used accordingly, and results reported as in routine clinical practice. Two laboratories, which used the AmoyDx® EGFR 29 Mutations Detection Kit (AmoyDx) with Cobas® cfDNA Sample Preparation Kit and QX200 Droplet Digital PCR (ddPCR) with the QIAamp Circulating Nucleic Acid Kit identified all ten samples correctly. Cobas® EGFR Mutation Test v2 (Cobas), the NGS methods, and the IdyllaTM detection method used in this study performed within the known sensitivity range of each detection method. Conclusions: If a negative result was obtained from methods with lower sensitivity (e.g. Cobas), repeated liquid biopsy testing and/or tissue biopsy analysis should be performed whenever possible, with the aim of identifying T790M-positive patients to allow them to receive the optimal second-line treatment with a third-generation EGFR TKI.
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To retrospectively evaluate the efficacy and safety of gefitinib in elderly patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor mutations.Nine patients aged 70 years or older who had advanced NSCLC with mutations of the epidermal growth factor receptor gene were treated with gefitinib, 250 mg daily. Clinical data, types of epidermal growth factor receptor mutations, efficacy and toxicity of gefitinib were evaluated in these patients. Tumor responses were assessed by computed tomography scan using the Response Evaluation Criteria in Solid Tumors.Six patients showed a partial response, and the other three exhibited stable disease. The overall response rate was 66.7%. The median progression-free survival was 396 days, whereas the median over all survival was 523 days. No serious toxicities were observed.Gefitinib is very efficacious and safe for elderly patients with adenocarcinoma of the lung harboring an EGFR tyrosine kinase mutation. The present data support the use of gefitinib in this particular subgroup.
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