Detection of low-level EGFR T790M mutation in lung cancer tissues

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.

Comparison of Detection of Epidermal Growth Factor Receptor (EFGR) Gene Mutation in Peripheral Blood Plasma (Liquid Biopsy) with Cytological Specimens in Lung Adenocarcinoma Patients

The ctDNA plasma testing is one of the methods to examine biomarkers for lung adenocarcinoma in order to detect a mutation of epidermal growth factor receptor (EGFR) gene. The advantages of ctDNA testing over tissue biopsy and lung tumor cytology include less invasive, faster result, cheaper, and minimum risk of complication for the patient. We analyzed and compare the detection of EFGR mutation in peripheral blood plasma (liquid biopsy) with cytological specimens of patients with lung adenocarcinoma. We conducted ctDNA plasma testing in 124 lung adenocarcinoma patients who visited our hospital from January to December 2018. The ctDNA testing results were compared with the results of EGFR detection from the previous cytological specimen examination. Most of the patients were males, aged 55-59 years, nonsmokers, and had stage IVA lung adenocarcinoma, with most metastasis found in the pleura. We found a correlation between EGFR prevalence with nonsmoking status and patient's age. The ctDNA plasma testing detected 27.4% common EGFR mutation and 72.6% wild-type EGFR. The figures of EGFR mutation detection from cytological specimens were 47.6% and 52.4%, respectively. Compared to cytological specimens, the EGFR mutation detection in ctDNA had a sensitivity of 48.3%, with a specificity of 90.9%, PPV of 82.35%, NPV of 66.7%, and 70.97% concordance rate. EGFR mutation with cytological specimen examination was more accurate than ctDNA.

Poor Prognosis With Coexistence Of EGFR T790M Mutation And Common EGFR-Activating Mutation In Non- Small Cell Lung Cancer

Purpose

Previous studies have shown that the presence of EGFR T790M mutation may reduce the treatment efficacy of tyrosine kinase inhibitors (TKIs) in EGFR-mutant lung cancer. However, little is known about the clinical features and outcomes of EGFR T790M mutation in pretreated patients with NSCLC.

Patients and methods

The clinical features of EGFR-activating and T790M mutations were assessed in a large cohort of patients with EGFR-TKI-naïve NSCLC (all/EGFR mutations, n=16,347/7,687). The correlation between the pretreatment T790M mutation status and clinical outcomes was evaluated using univariate and multivariate analyses.

Results

Pretreatment T790M mutation was reported in 1.39% of the patients and coexisted with an EGFR-activating or uncommon mutation. The dual EGFR T790M and common EGFR-activating mutations were more likely to be detected in lung adenocarcinoma, whereas single T790M mutation was more prevalent in non-adenocarcinomas. The presence of de novo T790M mutation correlated with reduced recurrence-free survival (RFS) in patients with NSCLC (odds ratio [OR] 3.37, 95% confidence interval [CI] 1.67-6.79, P = 0.001). After molecular stratification, T790M mutation was shown to exert adverse effects on the RFS of EGFR 19-del group (OR 2.89, 95% CI 1.10-7.91, P = 0.028) and EGFR L858R group (OR 3.43, 95% CI 1.33-8.88, P = 0.013). Furthermore, pretreatment T790M mutation promoted tumor metastasis to different sites.

Conclusion

T790M-positive tumors presented special clinical features, and the coexistence of T790M and common EGFR-activating mutations was associated with poor prognosis in patients with NSCLC.

Significant benefits of osimertinib in treating acquired resistance to first-generation EGFR-TKIs in lung squamous cell cancer: A case report

BACKGROUND

Lung squamous cell cancer (LSCC) rarely harbors epidermal growth factor receptor (EGFR) mutations, even much rarer for acquired T790M mutation. Although clinical trials of AURA series illustrated that non-small cell lung cancer (NSCLC) with EGFR T790M mutation can benefit from osimertinib, only five LSCC patients were enrolled in total; moreover, the efficacy for LSCC was not shown in the results. Therefore, the response of LSCC to osimertinib is still unclear to date.

CASE SUMMARY

We report an LSCC case with T790M-related acquired resistance after treatments with first-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs) and benefited from osimertinib significantly. A 63-year-old Chinese man was diagnosed with stage IV (cT2N2M1b) LSCC harboring an EGFR exon 19-deletion mutation. Following disease progression after gefitinib and multi-line chemotherapy, re-biopsy was conducted. Molecular testing of EGFR by amplification refractory mutation system-polymerase chain reaction detected the exon 19-deletion without T790M mutation. Therefore, the patient was given erlotinib, but progression developed only 3 mo later. Then the frozen re-biopsy tissue was tested by next-generation sequencing (NGS), which detected an EGFR T790M mutation. However, he was very weak with symptoms of dysphagia and cachexia. Fortunately, osimertinib was started, leading to alleviation from the symptoms. Four months later, normal deglutition was restored and partial response was achieved. Finally, the patient achieved an overall survival time period of 29 mo.

CONCLUSION

Our findings highlight that EGFR T790M mutation may also be an important acquired drug resistance mechanism for LSCC and offer direct evidence of the efficacy of osimertinib in LSCC with T790M mutation. NGS and better preservation conditions may contribute to higher sensitivity of EGFR T790M detection.

[Advanced Research on Non-small Cell Lung Cancer with De Novo T790M Mutation]

随着检测技术的发展，原发T790M突变检出率不断增加，三代表皮生长因子受体（epidermal growth factor receptor, EGFR）酪氨酸激酶抑制剂（tyrosine kinase inhibitors, TKIs）出现为其提供治疗机会。临床常重视继发T790M突变，而对原发T790M突变忽视或关注度不够。本综述发现原发T790M突变发生率波动大，主要受检测技术影响。原发T790M突变丰度多较低，易合并其他基因改变，是不良的预测和预后指标，一代和二代EGFR-TKIs疗效欠佳，奥希替尼的治疗价值有待研究。

Ultra-sensitive EGFR T790M Detection as an Independent Prognostic Marker for Lung Cancer Patients Harboring EGFR del19 Mutations and Treated with First-generation TKIs

PURPOSE

The detection of preexisting EGFR ^T790M subclones and the assessment of their clinical significance in the pretreatment of patients with EGFR ^T790M non-small cell lung cancer (NSCLC) remain unclear.

EXPERIMENTAL DESIGN

A total of 179 tumor samples from patients treated or not with a first-generation tyrosine kinase inhibitor (TKI) was analyzed. The presence of ultra-low levels of preexisting EGFR^T790M mutation was evaluated using ultra-sensitive droplet digital PCR (ddPCR) and the clinical implication of these mutations on first-generation TKI efficiency assessed.

RESULTS

With a ddPCR linear performance of 0.999 and an analytical sensitivity of approximately 0.001%, we observed a 66% (99/150) overall incidence of ultra-low EGFR ^T790M mutation. Among 82 patients harboring EGFR ^activating mutations, the presence of a preexisting EGFR ^T790M mutation prior to any treatment was significantly associated with a longer progression-free survival (PFS; P = 0.009; log-rank test). Interestingly, longer PFS was linked to concomitant EGFR ^del19 and ultra-low EGFR ^T790M mutations. Moreover, the presence of both EGFR ^del19 and ultra-low EGFR ^T790M mutations was identified as the best fit for predicting the clinical outcome of patients treated with TKI compared with an ultra-low EGFR ^T790M mutation status or an activating mutation alone (P = 0.042 and P = 0.0071, respectively).

CONCLUSIONS

We demonstrate that the detection of the ultra-low EGFR ^T790M mutation in TKI-naïve patients is not a rare event. We suggest that ddPCR should be used in clinical practice to distinguish patients who may respond to first- or third-generation TKIs.

Detection of EGFR and BRAF mutations by competitive allele-specific TaqMan polymerase chain reaction in lung adenocarcinoma

Epithelial growth factor receptor (EGFR)-tyrosine kinase inhibitors are the standard first-line treatment for patients with metastatic non-small cell lung cancer (NSCLC) expressing sensitive EGFR-mutants. Other drugs target different driver mutants, including the serine/threonine-protein kinase B-raf (BRAF) inhibitor dabrafenib, which has exhibited promising efficacy for treating patients with metastatic BRAF-mutated NSCLC. Therefore, identifying patients carrying mutations that may be treated using targeted therapies is important. However, the methods of molecular detection presently applied in clinical practice, particularly detection of BRAF in NSCLC patients, require further investigation. Therefore, more sensitive and economic methods are required. The present study applied the competitive allele-specific TaqMan polymerase chain reaction (CastPCR) technology to the molecular detection of EGFR (del2235-2249, del2236-2250, T790M, L858R) and BRAF (V600E, G469A, D594G) mutations in 144 treatment-naive patients with lung adenocarcinoma, and analyzed the association between the mutation rates and patients' clinicopathological features. 51.4% (74/144) cases were identified harboring EGFR mutations. A total of 40.3% (58/144) patients carried sensitizing mutations (exon 19 deletion or L858R) and 14.6% (21/144) carried T790M mutations. 6.9% (10/144) mutation-positive patients were double-mutated. Total EGFR mutation rate was significantly increased in female compared with that of males (60.9 vs. 43.8%, P<0.05), in non-smokers compared with that of smokers (62.8 vs. 34.5%, P<0.05). In total, 8.3% (12/144) patients were identified with BRAF mutations. 16.7% were V600E (2/12) and 83.3% (10/12) were non-V600E mutants. Among the 10 non-V600E mutations, D594G accounted for 90.0% (9/10) and G469A accounted for 10.0% (1/10). Statistical analysis demonstrated that the BRAF mutation rate was not associated with any of the following clinicopathological features: Sex, age, smoking history, clinical stages, distant metastasis, differentiation degree, tumor size and regional lymph node metastasis (P≥0.05). CastPCR technology is a robust method with high sensitivity for the molecular detection of EGFR and BRAF mutations in clinical formalin-fixed paraffin-embedded samples.

Comparison of cross-platform technologies for EGFR T790M testing in patients with non-small cell lung cancer

Somatic mutations in the gene encoding epidermal growth factor receptor (EGFR) play an important role in determining targeted treatment modalities in non-small cell lung cancer (NSCLC). The EGFR T790M mutation emerges in approximately 50% of cases who acquire resistance to tyrosine kinase inhibitors. Detecting EGFR T790M mutation in tumor tissue is challenging due to heterogeneity of the tumor, low abundance of the mutation and difficulty for re-biopsy in patients with advanced disease. Alternatively, circulating tumor DNA (ctDNA) has been proposed as a non-invasive method for mutational analysis. The presence of EGFR mutations in ctDNA predicts response to the EGFR TKIs in the first-line setting. Molecular testing is now considered a standard care for NSCLC. The advent of standard commercially available kits and targeted mutational analysis has revolutionized the accuracy of mutation detection platforms for detection of EGFR mutations. Our review provides an overview of various commonly used platforms for detecting EGFR T790M mutation in tumor tissue and plasma.

Meta-analysis of the impact of de novo and acquired EGFR T790M mutations on the prognosis of patients with non-small cell lung cancer receiving EGFR-TKIs

Purpose

The purpose of this meta-analysis was to explore the influences of pretreatment de novo and posttreatment-acquired epidermal growth factor receptor (EGFR) T790M mutations in patients with advanced non-small cell lung cancer (NSCLC) who had received tyrosine kinase inhibitors (TKIs).

Methods

We searched PubMed, Embase, and the China National Knowledge Infrastructure database for eligible literature. Data were extracted to assess the hazard ratios (HRs) for progression-free survival (PFS), overall survival (OS), and post-progression survival (PPS) and the relative ratios (RRs) for objective response rate (ORR).

Results

This meta-analysis included 22 studies comprising 1,462 patients with NSCLC who harbored activating EGFR mutations and were treated with EGFR-TKIs. Compared to pretreatment T790M mutation-negative NSCLC, pretreatment T790M mutation-positive NSCLC was associated with decreased PFS (HR 2.23, P<0.001) and OS (HR 1.55, P=0.003). A trend toward significance of worsening ORR (RR 0.86, P=0.051) was evident. The acquired T790M mutation was correlated with improved PFS (HR 0.75, P=0.006) and PPS (HR 0.57, P<0.001), compared to patients without the T790M mutation who progressed after EGFR-TKI treatment. There were no significant differences in OS or ORR between patients with acquired T790M mutation-positive and T790M mutation-negative NSCLC. However, in the tumor tissue rebiopsy subgroup, patients with acquired T790M mutation had improved OS (HR 0.60, P<0.001) compared to T790M mutation-negative patients. In the plasma ctDNA subgroup, acquired T790M mutation decreased the OS (HR 1.87, P<0.001).

Conclusion

Pretreatment T790M mutation was associated with worse PFS and OS in patients with advanced NSCLC treated with EGFR-TKIs, while acquired T790M mutation was associated with longer PFS and PPS than T790M mutation-negative NSCLC. The effects on OS were different between acquired T790M mutation detected from rebiopsy of tumor tissue and that detected from plasma ctDNA.

Evolution from genetics to phenotype: reinterpretation of NSCLC plasticity, heterogeneity, and drug resistance

Lung cancer is the leading cause of cancer-related deaths worldwide. Targeted therapy is beneficial in most cases, but the development of drug resistance stands as an obstacle to good prognosis. Multiple mechanisms were explored such as genetic alterations, activation of bypass signaling, and phenotypic transition. These intrinsic and/or extrinsic dynamic regulations facilitate tumor cell survival in meeting the demands of signaling under different stimulus. This review introduces lung cancer plasticity and heterogeneity and their correlation with drug resistance. While cancer plasticity and heterogeneity play an essential role in the development of drug resistance, the manipulation of them may bring some inspirations to cancer prognosis and treatment. That is to say, lung cancer plasticity and heterogeneity present us with not only challenges but also opportunities.

A sensitive and practical method to detect the T790M mutation in the epidermal growth factor receptor

The current study aimed to develop a method to rapidly, sensitively and practically screen for the epidermal growth factor receptor (EGFR) T790M mutation. This method combines an allele-specific competitive blocker (ACB) with a TaqMan quantitative polymerase chain reaction (PCR) amplification refractory mutation system (ARMS) in a one-step reaction. Using a mimic of a human genomic DNA panel containing serially diluted mutant alleles, the performance efficacy of this method was assessed. Using this method, the EGFR T790M mutation was detected in tyrosine kinase inhibitor (TKI)-naïve samples obtained from 27 non-small cell lung cancer (NSCLC) patients with EGFR-activating mutations. The association between de novo T790M mutations and the clinical benefit of EGFR-TKI treatment was also analysed. The sensitivity of this method was as low as 0.01%. In the samples from the 27 NSCLC patients, this method identified 6 mutant patients (22.2%), which was higher than the detection rate with scorpion ARMS (0.0%). No clinical variables were associated with the occurrence of a de novo T790M mutation. The median progression-free survival time in the TKI-naïve patients with a T790M mutation was shorter that that of patients without the mutation, but the difference was not significant (3.2 vs. 19.5 months, respectively; P=0.256). The median overall survival time in the groups with or without T790M mutation also did not significantly differ (10 vs. 20 months, respectively; P=0.689). Overall, the ACB-ARMS PCR method could be useful for detecting the EGFR T790M mutation in clinical samples that contain only a small number of mutant alleles. The clinical significance of a de novo T790M mutation should be further investigated.

Detection of EGFR-TK domain-activating mutations in NSCLC with generic PCR-based methods

Somatic mutations in the epidermal growth factor receptor-tyrosine kinase (EGFR-TK) domain of non-small cell lung cancer (NSCLC) influence the responsiveness of these tumors to EGFR-TK inhibitors, indicating their usefulness as a predictive molecular marker. However, for mutation analysis, the amount of clinical material available from NSCLC patients is often very limited, suboptimally preserved, and composed of both normal and tumor cells. As a consequence, the total amount of recovered DNA is frequently very limited, with mutant alleles being often strongly underrepresented, and thus requiring highly sensitive methods for the detection of mutations. In the present study, EGFR mutation screening was performed on 210 NSCLC clinical samples by heminested polymerase chain reaction (PCR), followed by denaturing gradient gel electrophoresis (DGGE). Candidate mutations were further characterized by sequencing. Seventeen different types of pathogenic EGFR-TK domain mutations were detected in 55 of the 210 samples (26%). We reanalyzed 149 of the 155 samples in which no mutation was found by real-time PCR for the presence of recurrent exon 21 and exon 19 mutations using peptide nucleic acid probes in the PCR mix to increase sensitivity by mutant allele enrichment. Four additional samples with exon 19 mutations were detected. Thus, it is found that the relatively simple and inexpensive PCR-DGGE assay is already very sensitive for the detection of mutations in clinical samples, including samples with low tumor cellularity (10% or higher tumor cell content), although the sensitivity and speed of the assay can be further increased for a restricted panel of mutations by introducing peptide nucleic acid probes in the DGGE or real-time PCR-based assay.

Comparison of next-generation sequencing and mutation-specific platforms in clinical practice

OBJECTIVES

To compare next-generation sequencing (NGS) platforms with mutation-specific analysis platforms in a clinical setting, in terms of sensitivity, mutation specificity, costs, capacity, and ease of use.

METHODS

We analyzed 25 formalin-fixed, paraffin-embedded lung cancer samples of different size and tumor percentage for known KRAS and EGFR hotspot mutations with two dedicated genotyping platforms (cobas [Roche Diagnostics, Almere, The Netherlands] and Rotor-Gene [QIAGEN, Venlo, The Netherlands]) and two NGS platforms (454 Genome Sequencer [GS] junior [Roche Diagnostics] and Ion Torrent Personal Genome Machine [Life Technologies, Bleiswijk, The Netherlands]).

RESULTS

All platforms, except the 454 GS junior, detected the mutations originally detected by Sanger sequencing and high-resolution melting prescreening and detected an additional KRAS mutation. The dedicated genotyping platforms outperformed the NGS platforms in speed and ease of use. The large sequencing capacity of the NGS platforms enabled them to deliver all mutation information for all samples at once.

CONCLUSIONS

Sensitivity for detecting mutations was highly comparable among all platforms. The choice for either a dedicated genotyping platform or an NGS platform is basically a trade-off between speed and genetic information.

Low level epifluorescent detection of nanoparticles and DNA on dielectrophoretic microarrays

Common epifluorescent microscopy lacks the sensitivity to detect low levels of analytes directly in clinical samples, such as drug delivery nanoparticles or disease related DNA biomarkers. Advanced systems such as confocal microscopes may improve detection, but several factors limit their applications. This study now demonstrates that combining an epifluorescent microscope with a dielectrophoretic (DEP) microelectrode array device enables the detection of nanoparticles and DNA biomarkers at clinically relevant levels. Using DEP microarray devices, nanoparticles and DNA biomarkers are rapidly isolated and concentrated onto specific microscopic locations where they are easily detected by epifluorescent microscopy. In this study, 40nm nanoparticles were detected down to 2-3 × 10(3) /ul levels and DNA was detected down to the 200 pg/ml level. The synergy of epifluorescent microscopy and DEP microarray devices provides a new paradigm for DNA biomarker diagnostics and the monitoring of drug delivery nanoparticle concentrations.

Presence of the minor EGFR T790M mutation is associated with drug-sensitive EGFR mutations in lung adenocarcinoma patients

The T790M mutation in the epidermal growth factor receptor (EGFR) gene is known to be associated with the acquired resistance of lung adenocarcinoma patients to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). The minor T790M mutant allele is occasionally detected in EGFR-TKI-naive tumor samples, yet findings concerning the clinical impact of the minor T790M mutation vary among previous studies. In the present study, we assessed the clinical impact of the minor T790M mutation using a novel, highly sensitive assay combining high-resolution melting (HRM), mutant-enriched PCR and co-amplification at a lower denaturation temperature (COLD)-PCR. We determined the T790M mutational status in 146 surgically resected lung adenocarcinomas without a history of EGFR-TKI treatment using mutant-enriched COLD-HRM (MEC-HRM) and standard HRM assays. The sensitivities of the MEC-HRM and standard HRM assays for the detection of T790M-mutant alleles among wild-type alleles were 0.01 and 10%, respectively. Although the T790M mutation was not detected using a standard HRM assay, we identified 19 (13%) T790M mutations using the MEC-HRM assay and defined these 19 mutations as minor T790M mutations. The proportion of T790M alleles was <0.1% in 17 (84%) of the 19 samples. Multivariate analyses revealed that a minor T790M mutation was significantly associated with the presence of EGFR exon 19 deletions or the L858R mutation (both of which are drug-sensitive EGFR mutations) (P=0.04). In conclusion, the minor EGFR T790M mutations were present in 13% of EGFR-TKI-naive surgically resected lung adenocarcinomas and were associated with drug-sensitive EGFR mutations.

The application of real-time PCR technique to detect rare cell clones with primary T790M Substitution of EGFR gene in metastases of non-small cell lung cancer to central nervous system in chemotherapy naive patients

The time-limited efficacy of reversible EGFR-TKIs in patients with advanced non-small cell lung cancer (NSCLC) with EGFR gene activating mutations is associated with development of treatment resistance after some period of therapy. This resistance predominantly results from secondary mutations located in EGFR gene, especially T790M substitution. There is limited information available concerning the prevalence of primary T790M mutations in patients with metastatic NSCLC tumors before treatment with EGFR-TKIs. The aim of work was to assess the prevalence of de novo T790M mutations in EGFR gene in tissue samples from NSCLC metastatases in central nervous system (CNS) in both chemotherapy and EGFR-TKI naive NSCLC patients. We analyzed DNA samples isolated from paraffin-embedded tissue from CNS metastases for T790M mutations using real-time PCR and TaqMan probe against the T790M mutant sequence. The tissue samples were taken during palliative neurosurgery in 143 NSCLC patients. Amplification of the T790M-specific sequence was detected in 25 patients (17.5 %). The quantity of mutated DNA was less than 1 % in all samples with amplification, and in vast majority (20 patients, 14 % of all samples) it was even less that 0.1 %. In 5 patients (3.5 %) quantity of mutated DNA ranged from 0.1 to 1 % and true positive results of T790M mutation presence in these patients were most possible. Amplification of this sequence was not concurrent with common EGFR mutations and was not associated with sex, smoking status and pathological type of cancer. There is a possibility to detect the primary T790M mutation in brain metastases of NSCLC in EGFR-TKIs naïve patients.

The predictive role of pretreatment epidermal growth factor receptor T790M mutation on the progression-free survival of tyrosine-kinase inhibitor-treated non-small cell lung cancer patients: a meta-analysis

Purpose

Subclones bearing the epidermal growth factor receptor (EGFR) T790M mutation concomitant with deletional mutation in exon 19 (Del19) or a point mutation in exon 21 (L858R) have been reported in non-small cell lung cancer patients before any EGFR tyrosine-kinase inhibitor (TKI) treatment. The effect of pretreatment T790M mutation on the survival of patients with both mutations treated with EGFR TKI is still being debated.

Methods

A meta-analysis was undertaken to pool eligible trials to better elucidate whether pretreatment T790M mutation predicts a poorer outcome of EGFR TKI treatment. Hazard ratios and their 95% confidence intervals for progression-free survival (PFS) were extracted and used under the random-effects model.

Results

A total of 246 patients with activating EGFR mutation such as Del19 or L858R participated in four selected trials from 350 articles. The overall incidence of patients with pretreatment T790M mutation was 43.10% (106/246), ranging from 34.88% to 80.00% in the individual trials. The combined hazard ratio for PFS in all four eligible studies was 2.602 (95% confidence interval 1.011–6.695; P=0.047), indicating a shorter PFS in patients who had the T790M mutation before receiving EGFR TKI treatment. Heterogeneity testing indicated significant heterogeneity but the absence of publication bias.

Conclusion

The meta-analysis reported here found that pretreatment T790M mutation had a negative impact on the PFS of non-small cell lung cancer patients with a Del19 or L858R EGFR mutation who received EGFR TKI treatment.

The impact of EGFR T790M mutations and BIM mRNA expression on outcome in patients with EGFR-mutant NSCLC treated with erlotinib or chemotherapy in the randomized phase III EURTAC trial

PURPOSE

Concomitant genetic alterations could account for transient clinical responses to tyrosine kinase inhibitors of the EGF receptor (EGFR) in patients harboring activating EGFR mutations.

EXPERIMENTAL DESIGN

We have evaluated the impact of pretreatment somatic EGFR T790M mutations, TP53 mutations, and Bcl-2 interacting mediator of cell death (BCL2L11, also known as BIM) mRNA expression in 95 patients with EGFR-mutant non-small-cell lung cancer (NSCLC) included in the EURTAC trial (trial registration: NCT00446225).

RESULTS

T790M mutations were detected in 65.26% of patients using our highly sensitive method based on laser microdissection and peptide-nucleic acid-clamping PCR, which can detect the mutation at an allelic dilution of 1 in 5,000. Progression-free survival (PFS) to erlotinib was 9.7 months for those with T790M mutations and 15.8 months for those without, whereas among patients receiving chemotherapy, it was 6 and 5.1 months, respectively (P < 0.0001). PFS to erlotinib was 12.9 months for those with high and 7.2 months for those with low/intermediate BCL2L11 expression levels, whereas among chemotherapy-treated patients, it was 5.8 and 5.5 months, respectively (P = 0.0003). Overall survival was 28.6 months for patients with high BCL2L11 expression and 22.1 months for those with low/intermediate BCL2L11 expression (P = 0.0364). Multivariate analyses showed that erlotinib was a marker of longer PFS (HR = 0.35; P = 0.0003), whereas high BCL2L11 expression was a marker of longer PFS (HR = 0.49; P = 0.0122) and overall survival (HR = 0.53; P = 0.0323).

CONCLUSIONS

Low-level pretreatment T790M mutations can frequently be detected and can be used for customizing treatment with T790M-specific inhibitors. BCL2L11 mRNA expression is a biomarker of survival in EGFR-mutant NSCLC and can potentially be used for synthetic lethality therapies.

[Advanced research on T790M mutation in non-small cell lung cancer]

携带表皮生长因子受体（epidermal growth factor receptor, EGFR）基因活性突变的非小细胞肺癌（non-small cell lung cancer, NSCLC）晚期患者使用EGFR-受体酪氨酸激酶抑制剂（tyrosine kinase inhibitor, TKI）治疗后具有较好的临床获益，但大部分患者在使用该药治疗10个月后出现耐药现象。研究发现EGFR基因20号外显子T790M基因突变是导致EGFR-TKI耐药的最主要因素，但其作用机制至今未明。目前的研究结果显示T790M基因突变是一个独立的、好的预后因素，但其能否作为EGFR-TKI的疗效预测因子仍存在争议。近年来，针对NSCLC肿瘤中T790M基因突变的检测技术不断更新，针对T790M耐药的新的治疗策略也不断涌现。本文就NSCLC中T790M基因突变的耐药机制、临床意义、检测方法及应对策略等方面的最新研究进展进行综述。

Applying biomarker testing to clinical practice in lung cancer

SUMMARY Until recently, therapeutic options for lung cancer were limited, and the division into non-small-cell lung cancer and small-cell lung cancer and staging of the disease was adequate for treatment decisions in most lung cancer patients. With the discovery of new treatment options, new challenges emerged. This review focuses on recent diagnostic and predictive biomarkers in lung cancer. In addition, new techniques will enable us to perform more molecular analyses in a shorter timespan. These developments require a modern interaction between treating physicians and pathologists for optimal tissue management, allowing more molecular markers to be tested.