Analytic and Clinical Validation of an Ultrasensitive, Quantitative Polymerase Chain Reaction Assay for EGFR Mutation Analysis With Circulating Tumor DNA

Interpretation of Lung Cancer Plasma EGFR Mutation Tests in the Clinical Setting

OBJECTIVES

Comprehensive data synthesis of the clinical parameters that affect plasma EGFR mutation test results in non-small cell lung carcinoma is lacking. Although individual studies have suggested a variety of patient characteristics that can affect diagnostic accuracy, no unified conclusion has been reached.

METHODS

We analyzed 170 plasma EGFR mutation tests performed between 2015 and 2021 at our institution and carried out a systematic review and meta-analysis to identify clinical and imaging features that correlate with plasma EGFR mutation test sensitivity.

RESULTS

Data synthesis from 14 studies of 2,576 patients revealed that patients with stage IV disease had a significantly lower false-negative rate than those with stage I through III disease. For our institutional cohort, which consisted of 75 paired plasma and tissue tests that were assessable for diagnostic accuracy, the overall sensitivity was 70.59% (95% confidence interval, 56.17%-82.51%). Patients who had distant metastases and more suspicious lymph nodes on imaging findings correlated with a low false-negative rate.

CONCLUSIONS

While interpreting plasma EGFR mutation results, extra caution should be exercised for patients with early-stage, localized disease to accommodate the possibility of false-negative results. These meta-analyses and clinical data may enable clinicians to make evidence-based judgments for individual patients.

Driver and novel genes correlated with metastasis of non-small cell lung cancer: A comprehensive analysis

Although mutations of genes are crucial events in tumorigenesis and development, the association between gene mutations and lung cancer metastasis is still largely unknown. The goal of this study is to identify driver and novel genes associated with non-small cell lung cancer (NSCLC) metastasis. Candidate genes were identified using a novel comprehensive analysis, which was based on bioinformatics technology and meta-analysis. Firstly, EGFR, KRAS, ALK, TP53, BRAF and PIK3CA were identified as candidate driver genes. Further meta-analysis identified that EGFR (Pooled OR 1.33, 95% CI 1.19, 1.50; P < .001) and ALK (Pooled OR 1.52, 95% CI 1.22, 1.89; P < .001) mutations were associated with distant metastasis of NSCLC. Besides, ALK (Pooled OR 2.40, 95% CI 1.71, 3.38; P < .001) mutation was associated with lymph node metastasis of NSCLC. In addition, thirteen novel gene mutations were identified to be correlated with NSCLC metastasis, including SMARCA1, GGCX, KIF24, LRRK1, LILRA4, OR2T10, EDNRB, NR1H4, ARID4A, PRKCI, PABPC5, ACAN and TLN1. Furthermore, elevated mRNA expression level of SMARCA1 and EDNRB was associated with poor overall survival in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), respectively. Additionally, pathway and protein-protein interactions network analyses found the two genes were correlated with epithelial-mesenchymal transition process. In conclusion, mutations of EGFR and ALK were significantly correlated with NSCLC metastasis. In addition, thirteen novel genes were identified to be associated with NSCLC metastasis, especially SMARCA1 in LUAD and EDNRB in LUSC.

Druggable driver gene alterations in redefined large cell carcinoma in Chinese patients: an observational study

Background

Few reports have investigated the genetic status of large cell carcinoma (LCC) in Chinese patients under the 2015 World Health Organization (WHO) classification. We aimed to analyze the distribution of druggable driver gene alterations, including mutations in epidermal growth factor receptor (EGFR), Kirsten rat sarcoma 2 viral oncogene homolog (KRAS), proto-oncogene B-Raf (BRAF), and phosphatidylinositol-4,5 biphosphate 3-kinase catalytic subunit alpha (PIK3CA) and translocations in echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) and ROS proto-oncogene 1 (ROS1), in a large population of patients with LCC under the 2015 WHO classification, and to assess the clinical outcomes of patients with LCC harboring these genetic alterations.

Methods

A cohort of 322 patients with LCC resected between June 2015 and December 2018 was included in this study. The clinical characteristics of the patients and data on the distribution of EGFR, KRAS, BRAF, PIK3CA, EML4-ALK, and ROS1 alterations were retrospectively collected. The disease-free survival (DFS) of patients with LCC was analyzed using the log-rank test.

Results

Among the patients with redefined LCC, the proportion of males was much higher than that of females. Detection of LCC was more frequent in patients >60 years of age (71.4%). Mutations of EGFR were found in 3.6% of the LCC participants, predominantly in non-smokers. Mutations in KRAS were observed in 7.8% of the LCC patients, mainly in males and smokers. Mutations in PIK3CA and EML4-ALK translocations comprised 2.1% and 0.52% of the identified alterations, respectively. No alterations were identified in ROS1 and BRAF. After molecular stratification, no significant difference in DFS was identified between wild-type (WT) and mutation groups (29.91±3.83 vs. 25.33±6.04 months, P=0.48).

Conclusions

Under the 2015 WHO criteria, LCC was more frequently detected in elderly male patients with inferior prognoses. The frequency of EGFR and KRAS mutations was found to be the highest. Mutations in EGFR occurred more frequently in non-smokers, whereas KRAS mutations occurred predominantly in males and smokers. The PIK3CA mutations and EML4-ALK translocations were rare in patients with LCC. Our data revealed that the identification of clinically actionable molecular alterations in LCC may help guide personalized cancer treatment decisions in the future.

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.

Clinical And Imageological Features Of Lung Squamous Cell Carcinoma With EGFR Mutations

Purpose

To analyze the distribution of epidermal growth factor receptor (EGFR) mutations; characterize the clinical and imageological features of lung squamous cell carcinoma (LSCC) in a large population of patients; and assess correlations between clinical and imageological characteristics and clinical outcomes of LSCC patients harboring EGFR mutations.

Patients and methods

Three pathologists retrospectively evaluated the morphological and immunohistochemical data of 2,322 patients with LSCC resected between February 2013 and December 2017. Data on the distribution of EGFR mutations and the clinical and imageological characteristics of the patients were retrospectively collected. Correlations between the EGFR mutation status and clinical outcomes were evaluated using univariate and multivariate analyses.

Results

EGFR mutations were found in 3.4% of patients with LSCC and predominantly in female and non-smoking patients. Tumor lesions in patients with EGFR-positive mutations were more irregularly shaped than those in patients with EGFR-negative mutations (P = 0.045). In non-smoking patients with LSCC, the proportion of marked spiculation was significantly higher in the EGFR-positive group than in the EGFR-negative group (P = 0.043). No significant difference in recurrence-free survival was noted between LSCC patients harboring EGFR-positive and those harboring EGFR-negative mutations. No difference in metastases was observed between the EGFR-positive and EGFR-negative cohorts.

Conclusion

Female gender, non-smoking habit, irregularly shaped tumor, and marked spiculation might predict the presence of EGFR mutations in LSCC. The administration of tyrosine kinase inhibitors to patients with LSCC after screening for EGFR mutations based on their clinical and imageological features would likely result in a population with a greater sensitivity to afatinib.

Ultrasensitive and quantitative detection of EGFR mutations in plasma samples from patients with non-small-cell lung cancer using a dual PNA clamping-mediated LNA-PNA PCR clamp

Circulating tumour DNA (ctDNA) is a potential proxy for tumour tissues. However, the analysis of mutations and mutational abundance using ctDNA remains challenging because ctDNA is present at low levels. In addition, the concordance between plasma and tumour tissues requires further investigation by high-sensitivity techniques. Here, we established an ultrasensitive, quantitative method for detecting rare mutations in plasma samples based on a dual PNA clamping-mediated LNA-PNA PCR clamp (LNA-dPNA PCR clamp). The novelty of our method is the coupling of PNA clamping with one-tube nested PCR to dually block wild-type DNA amplification and efficiently amplify mutant DNA. Then, four hotspot EGFR mutations (EGFR L858R, EGFR Exon 19 deletion, EGFR T790M, and EGFR C797S) were detected by our proposed method. Finally, we evaluated the concordance between plasma and tumour tissues by simultaneously detecting EGFR L858R by ddPCR and LNA-dPNA PCR clamp in 132 tissues and matched plasma samples from patients with NSCLC. For the four EGFR mutations, the amplification sensitivity of the LNA-dPNA PCR clamp was 100 copies per reaction, and the linearity was from 100 to 106-107 copies per reaction. The limit of detection for the LNA-dPNA PCR clamp was 0.01%-0.1%. The LNA-dPNA PCR clamp was similarly consistent with ddPCR in quantifying mutational abundance (R2 = 0.9568) and exhibited similar limit of detection (0.01%-0.1% vs. 0.01%), sensitivity (19.6 vs. 21.7), specificity (94.2 vs. 91.9), and concordance (68.2 vs. 67.4) to those of ddPCR for ctDNA detection. In conclusion, the LNA-dPNA PCR clamp will provide a labour-saving, cost-saving, ultrasensitive tool for detecting and quantifying plasma EGFR mutations.

The diagnostic value of circulating tumor cells and ctDNA for gene mutations in lung cancer

PURPOSE

Detecting gene mutations by two competing biomarkers, circulating tumor cells (CTCs) and ctDNA has gradually paved a new diagnostic avenue for personalized medicine. We performed a comprehensive analysis to compare the diagnostic value of CTCs and ctDNA for gene mutations in lung cancer.

METHODS

Publications were electronically searched in PubMed, Embase, and Web of Science as of July 2018. Pooled sensitivity, specificity, and AUC, each with a 95% CI, were yielded. Subgroup analyses and sensitivity analyses were conducted. Quality assessment of included studies was also performed.

RESULTS

From 4,283 candidate articles, we identified 47 articles with a total of 7,244 patients for qualitative review and meta-analysis. When detecting EGFR, the CTC and ctDNA groups had pooled sensitivity of 75.4% (95% CI 0.683-0.817) and 67.1% (95% CI 0.647-0.695), respectively. When testing KRAS, pooled sensitivity was 38.7% (95% CI 0.266-0.519) in the CTC group and 65.1% (95% CI 0.558-0.736) in the ctDNA group. The diagnostic performance of ctDNA in testing ALK and BRAF was also evaluated. Heterogeneity among the 47 articles was acceptable.

CONCLUSION

ctDNA might be a more promising biomarker with equivalent performance to CTCs when detecting EGFR and its detailed subtypes, and superior diagnostic capacity when testing KRAS and ALK. In addition, the diagnostic performance of ctDNA and CTCs depends on the detection methods greatly, and this warrants further studies to explore more sensitive methods.

PCR-Stop analysis as a new tool for qPCR assay validation

Progressively more qPCR assays have been developed in recent years in numerous fields of application. These assays are routinely validated using calibration curves, but essential validation per se such as Poisson analysis is frequently neglected. However, validation is crucial for determination of resolution and quantitative and qualitative limits. The new test method PCR-Stop analysis presented in this work investigates assay performance during initial qPCR cycles. PCRs with one to five pre-runs are performed while the subsequent main qPCR runs reflect pre-run replication rates. Ideally, DNA doubles according to pre-runs, there is no variation between replicates and qPCR starts immediately at the first cycle with its average efficiency. This study shows two exemplary qPCR assays, both with suitable calibration curves and efficiencies. We demonstrated thereby the benefits of PCR-Stop analysis revealing quantitative and qualitative resolution of both assays, the limits of one of those assays and thus avoiding misinterpretations in qPCR analysis. Furthermore, data displayed that a well performing assay starts indeed with its average efficiency.