Analysis of EGFR mutation status in malignant pleural effusion and plasma from patients with advanced lung adenocarcinoma

Biomarkers in the management of lung cancer: changing the practice of thoracic oncology

Lung cancer currently represents a leading cause of cancer death. Substantial progress achieved in the medical therapy of lung cancer during the last decade has been associated with the advent of targeted therapy, including immunotherapy. The targeted therapy has gradually shifted from drugs suppressing general mechanisms of tumor growth and progression to agents aiming at transforming mechanisms like driver mutations in a particular tumor. Knowledge of the molecular characteristics of a tumor has become an essential component of the more targeted therapeutic approach. There are specific challenges for biomarker determination in lung cancer, in particular a commonly limited size of tumor sample. Liquid biopsy is therefore of particular importance in the management of lung cancer. Laboratory medicine is an indispensable part of multidisciplinary management of lung cancer. Clinical Chemistry and Laboratory Medicine (CCLM) has played and will continue playing a major role in updating and spreading the knowledge in the field.

Transcending Blood—Opportunities for Alternate Liquid Biopsies in Oncology

Simple Summary

Cell-free DNA—DNA that has been expelled from cells and can be isolated from blood plasma and other body fluids—is a useful tool in medicine, with applications as a biomarker in diagnosis, prognosis, disease profiling, and treatment selection. In oncology, the ease of access to the tumour genome is a major advantage of cell-free DNA, but while this has led to significant research in blood, other body fluids have not received equal attention. This review article summarises the current research into cell-free DNA in non-blood body fluids, highlighting its values and limitations, and suggesting the direction of future studies. We conclude that cell-free DNA from non-blood body fluids may provide additional information to supplement traditional biopsies, allowing informative and improved patient care across many cancer types.

Abstract

Cell-free DNA (cfDNA) is a useful molecular biomarker in oncology research and treatment, but while research into its properties in blood has flourished, there remains much to be discovered about cfDNA in other body fluids. The cfDNA from saliva, sputum, cerebrospinal fluid, urine, faeces, pleural effusions, and ascites has unique advantages over blood, and has potential as an alternative ‘liquid biopsy’ template. This review summarises the state of current knowledge and identifies the gaps in our understanding of non-blood liquid biopsies; where their advantages lie, where caution is needed, where they might fit clinically, and where research should focus in order to accelerate clinical implementation. An emphasis is placed on ascites and pleural effusions, being pathological fluids directly associated with cancer. We conclude that non-blood fluids are viable sources of cfDNA in situations where solid tissue biopsies are inaccessible, or only accessible from dated archived specimens. In addition, we show that due to the abundance of cfDNA in non-blood fluids, they can outperform blood in many circumstances. We demonstrate multiple instances in which DNA from various sources can provide additional information, and thus we advocate for analysing non-blood sources as a complement to blood and/or tissue. Further research into these fluids will highlight opportunities to improve patient outcomes across cancer types.

Cytology–Based Specimen Triage for Epidermal Growth Factor Receptor Mutation Testing of Malignant Pleural Effusions in Non–Small Cell Lung Cancer

Introduction

Malignant pleural effusions are common in non–small cell lung cancer (NSCLC). Molecular testing is among the most critical steps in the management of patients with advanced NSCLC. However, the optimal approach for epidermal growth factor receptor (EGFR) mutation testing in such effusion samples remains unclear.

Methods

We prospectively collected effusion samples from patients with EGFR–mutant NSCLC. Following sample centrifugation, genomic DNA and cell–free DNA were respectively extracted from the sediment and supernatants. EGFR mutation was detected through a real–time PCR assay.

Results

A total of 108 effusions from 78 patients were examined, with 12 and 96 obtained before and after EGFR tyrosine kinase inhibitor treatment, respectively. Carcinoma cells or atypical cells were identified in 73 effusions (67.6%). EGFR mutations were detected in 86 (79.6%) sediment and 84 (77.8%) supernatant samples. Among the effusions with positive cytological findings, the EGFR mutation detection rates were 95.9% (70/73) and 86.3% (63/73) in the sediment and supernatants, respectively. Among the effusions with negative cytological findings, the corresponding detection rates were 45.7% (16/35) and 60% (21/35), respectively. Current clinical practice is to arrange EGFR mutation testing only for sediment from cytologically positive effusions. Through the proposed cytology–based specimen triage, wherein sediment and supernatants with positive and negative cytological findings, respectively, are tested, the detection rate was increased from 64.8% (70/108) to 84.3% (91/108). At half of the cost, this strategy provided a detection rate only slightly lower than the rate in a combined test of all the sediment and supernatants (87.0%, 94/108).

Conclusions

The separate extraction of DNA from sediment and supernatants obtained from centrifuged effusion samples can improve the overall EGFR mutation detection rate. The present cytology–based specimen triage is an efficient strategy for EGFR mutation testing in patients with EGFR–mutant NSCLC.