EGFR mutation genotyping and ALK status determination in liquid-based cytology samples of non-small cell lung cancer

Advances in diagnostic liquid-based cytology

Liquid-based cytology (LBC) has changed the landscape of gynaecological cytology. A growing demand exists for LBC in diagnostic cytology, particularly for ancillary testing, such as immunocytochemistry and molecular testing. Ancillary testing solely based on conventional preparation (CP) methods remains challenging. Recently, the increased demand for specialist testing and minimally invasive techniques, such as endoscopic ultrasonography fine-needle aspiration, to obtain cellular samples has led to an increasing demand for ancillary testing on cytology LBC supernatant, slides and cell block (CB). This facilitates the diagnosis and prognosis in cytology samples enabling personalized treatment. An understanding of the history and future prospects of LBC is crucial for its application in routine diagnostics by cytopathologists and cytotechnologists. In this review, we initiated an internet search using the keyword 'liquid-based cytology', and we conducted a literature review to discuss the usefulness of combined diagnosis of LBC and CP, immunocytochemistry and molecular testing and assessed the quality of nucleic acids in diagnostic LBC. High-quality and cell-rich diagnostic LBC surpassed the CP method alone in terms of reliability and versatility of ancillary testing in cytological diagnosis. Conclusively, diagnostic LBC lends itself to various new technologies and is expected to continue evolving with innovations in the future.

Comparison of Confirmed Cytology Smears and Cell Blocks for Epidermal Growth Factor Receptor Mutation Testing in Non-Small Cell Lung Cancer

INTRODUCTION

Various cytologic specimens have been used to diagnose epidermal growth factor receptor (EGFR) gene mutations in non-small cell lung cancer (NSCLC). However, insufficient samples and lengthy DNA extraction procedures have led to inconsistent diagnostic results. To reduce manipulation losses and improve DNA extraction quality, we provide an improved procedure for DNA extraction from smear samples containing rare tumor cells in NSCLC.

PATIENTS AND METHODS

The effectiveness of this new method for DNA extraction and diagnosis was validated in 8 patients with pleural effusion smears and formalin-fixed paraffin-embedded cell blocks, and another with 2 smears. Smear samples with <5% tumor cells were collected, and visible particles were selected for DNA extraction after centrifugation. Qiagen formalin-fixed paraffin-embedded DNA extraction kit (Qiagen) was used for DNA extraction and the procedure was modified. The EGFR mutation analysis in both types of material used the EGFR mutation analysis kit (Therascreen EGFR RGQ PCR) and real-time polymerase chain reaction (Rotor-Gene Q).

RESULTS

The DNA extraction amount of the smear was 2.6 to 258.8 ng/μL, and that of the cell block was 1.4 to 139.9 ng/μL. The DNA quantity and purity of DNA extracts isolated from both sample sources were sufficient for subsequent EGFR mutation detection, where mutation rates were similar and diagnostic results were consistent when smears or cell blocks were used.

CONCLUSION

This improved method demonstrates that cytology smears can be used as a test material for the detection of EGFR mutations in patients with NSCLC with sparse cells.

Guidelines for Handling of Cytological Specimens in Cancer Genomic Medicine

Rapid advances are being made in cancer drug therapy. Since molecularly targeted therapy has been introduced, personalized medicine is being practiced, pathological tissue from malignant tumors obtained during routine practice is frequently used for genomic testing. Whereas cytological specimens fixed mainly in alcohol are considered to be more advantageous in terms of preservation of the nucleic acid quality and quantity. This article is aimed to share the information for the proper handling of cytological specimens in practice for genomic medicine based on the findings established in "Guidelines for Handling of Cytological Specimens in Cancer Genomic Medicine (in Japanese)" published by the Japanese Society of Clinical Cytology in 2021. The three-part practical guidelines are based on empirical data analyses; Part 1 describes general remarks on the use of cytological specimens in cancer genomic medicine, then Part 2 describes proper handling of cytological specimens, and Part 3 describes the empirical data related to handling of cytological specimens. The guidelines indicated proper handling of specimens in each fixation, preparation, and evaluation.

Performance of a 50-gene next generation sequencing panel with post-centrifuge supernatant cytology fluid in non-small-cell lung cancer

BACKGROUND

Liquid based cytology (LBC) specimens are increasingly utilized for molecular analysis, as results are comparable to molecular analysis performed on traditional specimens (biopsy or cell block). However, there are few studies demonstrating the long-term viability of DNA in LBC samples.

METHODS

In this study, a 50-gene next generation sequencing (NGS) panel was performed on DNA isolated from post-centrifuged supernatant LBC samples of cases of non-small-cell lung carcinoma. Comparison was made to results of an identical NGS panel performed on a concurrent clinical sample (biopsy or cell block). Quality parameters including DNA concentration, total reads, amplicons with reads under 450 and 350, and variant allele fraction were also compared. For a subset of LBC samples, DNA was isolated after being held for varying extended lengths of time after collection (up to 41 days) at 5°C and results compared.

RESULTS

Results of NGS mutation analysis were concordant between LBC samples and clinical samples. DNA concentration was on average higher in the LBC samples compared to the clinical samples. The remaining metrics were more variable, but illustrated the adequacy of LBC samples for NGS testing. DNA isolated from LBC samples held for longer periods of time was of good concentration. NGS analysis was successfully performed on all samples, with concordance with results of clinical samples.

CONCLUSION

DNA isolated directly from LBC fluid is suitable for NGS analysis. DNA is also stable in LBC preservative for extended periods of time before isolation and NGS analysis can subsequently be successfully performed.

Case Report: Treatment of Alectinib in NSCLC With Brain Metastasis Patient Refractory to Radiotherapy After Resistance to Crizotinib

Background

Brain metastasis is the most common form of tumor recurrence after resistance to crizotinib in patients with anaplastic lymphoma kinase (ALK)-positive non-small-cell lung cancer (NSCLC). The treatment of brain metastasis in patients with ALK-positive NSCLC requires a multidisciplinary approach, including targeted therapy, chemotherapy, and radiotherapy. At present, no optimal treatment for these patients has been identified, although radiotherapy has remained a vital treatment.

Case Presentation

We experienced a patient with ALK-positive NSCLC who developed brain metastasis after crizotinib therapy. ALK rearrangement was not detected in a blood sample using next-generation sequencing. In accordance with National Comprehensive Cancer Network guidance, the patient underwent whole-brain radiotherapy. However, the number of metastatic sites unexpectedly increased. In desperation, the patient was empirically given alectinib after radiotherapy failure, and unanticipated success was achieved.

Conclusions

This case revealed some new insights. First, liquid biopsy is complementary to tissue biopsy in patients with NSCLC, mainly in those with EGFR mutation. However, ALK rearrangement should be assessed using tissue biopsy as much as possible. Second, brain metastasis of NSCLC might respond to second-generation tyrosine kinase inhibitors (TKIs), such as alectinib and ceritinib, after resistance to crizotinib regardless of the presence or absence of ALK rearrangement in liquid biopsy. Finally, combined radiotherapy and TKI therapy appears optimal in patients with brain metastasis of NSCLC after resistance to crizotinib in the absence of a definitive driver gene.

What Is New in Biomarker Testing at Diagnosis of Advanced Non-Squamous Non-Small Cell Lung Carcinoma? Implications for Cytology and Liquid Biopsy

The discovery and clinical validation of biomarkers predictive of the response of non-squamous non-small-cell lung carcinomas (NS-NSCLC) to therapeutic strategies continue to provide new data. The evaluation of novel treatments is based on molecular analyses aimed at determining their efficacy. These tests are increasing in number, but the tissue specimens are smaller and smaller and/or can have few tumor cells. Indeed, in addition to tissue samples, complementary cytological and/or blood samples can also give access to these biomarkers. To date, it is recommended and necessary to look for the status of five genomic molecular biomarkers (EGFR, ALK, ROS1, BRAFV600, NTRK) and of a protein biomarker (PD-L1). However, the short- and more or less long-term emergence of new targeted treatments of genomic alterations on RET and MET, but also on others’ genomic alteration, notably on KRAS, HER2, NRG1, SMARCA4, and NUT, have made cellular and blood samples essential for molecular testing. The aim of this review is to present the interest in using cytological and/or liquid biopsies as complementary biological material, or as an alternative to tissue specimens, for detection at diagnosis of new predictive biomarkers of NS-NSCLC.

Detecting Resistance to Therapeutic ALK Inhibitors in Tumor Tissue and Liquid Biopsy Markers: An Update to a Clinical Routine Practice

The survival of most patients with advanced stage non-small cell lung cancer is prolonged by several months when they are treated with first- and next-generation inhibitors targeting ALK rearrangements, but resistance inevitably emerges. Some of the mechanisms of resistance are sensitive to novel ALK inhibitors but after an initial tumor response, more or less long-term resistance sets in. Therefore, to adapt treatment it is necessary to repeat biological sampling over time to look for different mechanisms of resistance. To this aim it is essential to obtain liquid and/or tissue biopsies to detect therapeutic targets, in particular for the analysis of different genomic alterations. This review discusses the mechanisms of resistance to therapeutics targeting genomic alterations in ALK as well as the advantages and the limitations of liquid biopsies for their identification.

Survival of Lung Cancer Patients Dependent on the LOH Status for DMP1, ARF, and p53

Lung cancer is the leading cause of cancer deaths in the world, and accounts for more solid tumor deaths than any other carcinomas. The prognostic values of DMP1, ARF, and p53-loss are unknown in lung cancer. We have conducted survival analyses of non-small cell lung cancer (NSCLC) patients from the University of Minnesota VA hospital and those from the Wake Forest University Hospital. Loss of Heterozygosity (LOH) for hDMP1 was found in 26 of 70 cases (37.1%), that of the ARF/INK4a locus was found in 33 of 70 (47.1%), and that of the p53 locus in 43 cases (61.4%) in the University of Minnesota samples. LOH for hDMP1 was associated with favorable prognosis while that of p53 predicted worse prognosis. The survival was much shorter for ARF-loss than INK4a-loss, emphasizing the importance of ARF in human NSCLC. The adverse effect of p53 LOH on NSCLC patients' survival was neutralized by simultaneous loss of the hDMP1 locus in NSCLC and breast cancer, suggesting the possible therapy of epithelial cancers with metastatic ability.

Evaluation of liquid based cytology in detection of EGFR mutation in NSCLC by large samples

Background

Cytology samples are the main resources to detect driver oncogene alterations for advanced lung cancer patients. To explore the value of liquid-based cytology in the detection of epidermal growth factor receptor (EGFR) mutation in non-small cell lung cancer (NSCLC), we analyzed data from a large cohort of EGFR mutation-positive patients.

Methods

We analyzed the clinicopathological characteristics of 8,029 NSCLC cases tested for EGFR mutation by liquid-based cytology specimens and 1,934 NSCLC cases tested by formalin-fixed and paraffine-embedded (FFPE) samples in the Shanghai Pulmonary Hospital from September 2015 to December 2019. Before detection, we evaluated the number of tumor cells in the liquid-based cytology slide, and samples with more than 50 tumor cells and visible sediment were selected for DNA extraction after centrifugation.

Results

The positive rate of EGFR mutation in liquid-based cytology-tested cases was 47.18%, higher than the 41.37% tested through FFPE sample (P<0.01). Accordingly, the mutation rate of EGFR in adenocarcinoma (AC) and NSCLC was higher than that of the FFPE sample (60.01% vs. 54.15%, P<0.01; 30.54% vs. 21.99%, P<0.01). The positive rate of EGFR mutation in pleural effusion was 62.67%, which was the highest rate among liquid-based cytology sample t (P<0.01).

Conclusions

Using quality control and standard procedure, it was found that liquid-based cytology specimen testing is a convenient and reliable method of EGFR detection, as validated by analysis of a large cohort. EGFR mutation detection should also be carried out in NSCLC patients diagnosed by cytology more than in AC patients.