Bronchoscopic Brushing from Central Lung Cancer-Next Generation Sequencing Results are Reliable

Suitability of frozen cell pellets from cytology specimens for the Amoy 9-in-1 assay in patients with non-small cell lung cancer

BACKGROUND

The AmoyDx Pan lung cancer PCR panel (AmoyDx PLC panel) has been approved as a companion diagnostic tool for multiple anticancer agents in patients with non-small cell lung cancer (NSCLC). However, the suitability of cytology specimens as samples for the AmoyDx PLC panel remains unclear. We evaluated the performance of frozen cell pellets from cytology specimens (FCPs) in the Amoy 9-in-1 assay, a preapproval assay of the AmoyDx PLC panel.

METHODS

We retrospectively collected data of NSCLC patients enrolled in LC-SCRUM-Asia from the Shizuoka Cancer Center between September 2019 and May 2021.

RESULTS

A total of 49 cases submitted FCPs for evaluation of oncogenic driver alterations and were assessed using Amoy 9-in-1 and next-generation sequencing (NGS) assays. The success rates of DNA and RNA analyses using the Amoy 9-in-1 were both 100%, compared with 86% and 45%, respectively, using NGS assays. Oncogenic driver alterations were detected in 27 (55%) and 23 (47%) patients using Amoy 9-in-1 and NGS, respectively. No inconsistent results were observed among 19 cases in which both assays showed successful detection. In the remaining 30 cases, 10 had inconsistent results: nine oncogenic driver alterations (3 MET, 2 ALK, 2 ROS1, and 2 KRAS) were detectable only in Amoy 9-in-1, and one epidermal growth factor receptor (EGFR) mutation was detectable only in NGS.

CONCLUSION

FCPs can be successfully used in the AmoyDx PLC panel, with higher success rate compared with the NGS assay. The AmoyDx PLC panel may be an option in cases when insufficient tissue sample is available for the NGS assay.

Molecular Diagnostics of Lung Cancer in Serous Effusion Samples

For molecular diagnostics of lung cancer samples, often only a small amount of material is available. The ever-increasing number of biomarker testing is in contrast to the amount of material obtained. In that case, cytological specimens, such as serous effusion samples, are one possible option. Effusion samples were prepared as sediment smears or cytospins or as a cell block if needed. Suitable tumor cells areas were marked by a cytopathologist and used for molecular diagnostics, including fast track analysis, parallel sequencing, and/or fluorescence in situ hybridization. In 62 cases of malignant effusion with cells of pulmonary adenocarcinoma, molecular diagnostics were carried out. A fast-track result with the high-resolution melting method for hotspot mutation of KRAS Exon 2 and EGFR exon 21 and fragment length analysis of EGFR exon 19 was available for 43 out of 47 samples (92%). Parallel sequencing was successful for 56 out of 60 samples (93.3%). In the same period, 108 FISH analyses were performed for MET amplification, followed by ROS1, RET, and ALK translocation analysis. If only a limited amount of tissue/biopsy is available, a malignant effusion is advisable to perform on the molecular diagnostics with a high success rate.

Suitability of transbronchial brushing cytology specimens for next-generation sequencing in peripheral lung cancer

Next‐generation sequencing (NGS) enables the diagnosis of large numbers of gene aberrations during one examination, and precision medicine has been developed for patients with advanced non–small cell lung cancer (NSCLC). However, peripheral lung lesions account for the majority of advanced lung cancers, especially lung adenocarcinoma. In these cases, it is difficult to obtain tissue samples which contain sufficient tumor cells by transbronchial biopsy (TBB) with forceps. Even when the target lesions are quite small, bronchial brushing can obtain enough tumor cells by endobronchial ultrasonography using guide sheath (EBUS‐GS). In this study, we investigate the suitability of bronchial brushing cytology specimens obtained by EBUS‐GS‐TBB to evaluate the correlation between the success rate of NGS and extracted DNA/RNA yields according to biopsy method. We prospectively collected 222 tumor samples obtained from patients with advanced lung cancer. All patients were enrolled in a prospective nationwide genomic screening project for lung cancer (LC‐SCRUM‐Japan/Asia). Genomic data were obtained from the clinico‐genomic database of LC‐SCRUM‐Japan/Asia. The extraction yields of DNA/RNA from samples obtained by EBUS‐GS‐TBB were relatively low compared with tissue samples. The success rate of DNA sequencing for EBUS‐GS‐TBB was 97.9%, with no significant differences between biopsy methods. The success rate of RNA sequencing for EBUS‐GS‐TBB was 80.4%, which was relatively low compared with surgical biopsy samples (P = 0.069). However, some rare oncogenic driver aberrations were detected from these specimens. This study demonstrated that cytology samples obtained by transbronchial brushing with EBUS‐GS‐TBB were suitable for NGS analysis.

Bronchoscopic tissue yield for advanced molecular testing: are we getting enough?

The treatment of advanced lung cancer has become increasingly personalized over the past decade as a result of the improved understanding of tumor molecular biology and anti-tumor immunity. An adequate tumor sample is central to targetable mutation analysis, and immunologic profiling. The majority of lung cancer patients currently present at an advanced disease stage, so that diagnosis and staging are largely based on small biopsy and cytology specimens. Flexible bronchoscopy techniques play a prominent role in the acquisition of these diagnostic specimens. This narrative review summarizes the available evidence with regards to the role of various conventional and advanced flexible bronchoscopy techniques in acquiring sufficient tissue for mutation analysis and programmed death-ligand 1 (PD-L1) testing.

[Immunohistochemical and molecular pathological diagnosis of lung carcinoma]

The therapy of lung cancer has revolutionarily changed within the last 15 years. The prognosis of patients has dramatically improved due to targeted therapies, for instance tyrosine kinase inhibitors (TKI). Current recruiting studies are testing new MET-, KRAS-, ROS1-, RET- and NTRK-inhibitors. The first clinical data are promising, emphasizing that it remains a future challenge for pathologists and oncologists to keep an eye on all facets of therapy options. Today, precise lung cancer classification via immunohistochemistry and molecular pathology is crucial for the therapy and prognosis of patients. Further, new biopsy technologies lead to very small tumor tissue samples and cytological samples of high diagnostic quality. Therefore, the complexity of diagnosis needs a strategic procedure to minimize loss of tissue material. This assay gives an overview of efficient and target-orientated diagnostic procedures in consideration of current clinical trials.

[Molecular diagnostics of cytological specimens]

For lung carcinomas with certain molecular genetic alterations of the ALK, BRAF or EGFR gene, there are targeted therapies that are also approved as first-line therapy. Often, only limited sample material from biopsies is available for molecular pathological testing. In some cases, biopsies with standard and immunohistochemical staining have no or too low tumor content to be used for PCR-based examinations or fluorescence in situ hybridization (FISH) analyses. In such cases, cytological preparations such as bronchus brush smears, transbronchial needle aspiration (TBNA), bronchial lavage, puncture smears from lymph node or peripheral metastases, pleural effusion, ascites, and pericardial effusion can be used. Standard stainings such as HE, Pappenheim, and Papanicolaou as well as immunohistological preparations can be used after morphological analysis and confirmatory diagnosis in order to extract DNA from them or to use them for FISH analysis. A cytopathologist marks the tumor cell areas on the slide beforehand. It is only possible to dissect these areas and extract DNA if the proportion of tumor cells is sufficiently high. In order to carry out a FISH analysis with the cytological preparations, the cytopathologist must draw in areas as small as possible with more than 100 tumor cells. Already stained sections are destained before the hybridization reaction. The aim is to achieve comprehensive diagnostics even with limited starting material and to avoid re-biopsies. Between 2016 and July 2019, 1711 next generation sequencing (NGS) and FISH analyses were performed on cytological preparations at the Department of Pathology of the University Hospital of Cologne. The success rate of 85.9% for NGS examinations was slightly higher than the success rate of 82.8% for FISH analyses.