Testing for EGFR Variants in Pleural and Pericardial Effusion Cell-Free DNA in Patients With Non-Small Cell Lung Cancer

JAMA Oncol. 2023 Feb 1;9(2):261-265. doi: 10.1001/jamaoncol.2022.6109.

Abstract

Importance: Molecular testing in non-small cell lung cancer (NSCLC) is commonly limited by inadequate tumor sample. Plasma cell-free DNA (cfDNA) genotyping as a complementary test is specific but only moderately sensitive. Genotyping of cfDNA in pleural and pericardial effusion (PE-cfDNA) can further optimize molecular diagnostic yield and reduce the need for repeated biopsies.

Objective: To prospectively validate droplet digital polymerase chain reaction (ddPCR) for detection of sensitizing EGFR variants and acquired Thr790Met variant (T790M) from PE-cfDNA in patients with NSCLC.

Design, setting, and participants: This prospective diagnostic validation study was conducted between September 6, 2016, and January 21, 2021 at 2 major Hong Kong cancer centers. Patients with advanced NSCLC with both wild-type and variant EGFR status and exudative PE who underwent thoracocentesis or pericardiocentesis were randomly enrolled. Patients were either EGFR-tyrosine kinase inhibitor (TKI) naive (cohort 1) or EGFR-TKI treated but osimertinib naive (cohort 2). Enrolled patients underwent pleural- or pericardial-fluid and blood sampling for ddPCR EGFR testing. EGFR status results with ddPCR testing of PE-cfDNA and blood were compared with EGFR status in matched tumor biopsy or PE cell block samples.

Main outcomes and measures: Specificity, sensitivity, and concordance of PE-cfDNA for detection of sensitizing EGFR variants and acquired T790M variation.

Results: Among 171 patients (54% female) enrolled, there were 104 in cohort 1 and 67 in cohort 2. In cohort 1, 37% (38/102) were EGFR-variant positive; PE-cfDNA showed 97% sensitivity (95% CI, 92%-100%), 97% specificity (95% CI, 93%-100%), and 97% concordance (ĸ = 0.94, P < .001) for the detection of sensitizing EGFR variants. It was more sensitive than plasma in detecting sensitizing EGFR variants (97% vs 74%, P < .001). In cohort 2, 38% (15 of 40) were positive for the EGFR T790M variant; PE-cfDNA showed 87% sensitivity (95% CI, 69%-100%), 60% specificity (95% CI, 41%-79%), and 70% concordance (ĸ = 0.42, P = .004) for acquired T790M. The EGFR T790M variant was detected in 51% of PE-cfDNA vs 25% of PE cell block samples.

Conclusions and relevance: In this diagnostic study, EGFR variants could be accurately detected from PE-cfDNA in patients with NSCLC. More EGFR T790M was detected in PE-cfDNA than in guideline-recommended PE cell block preparations. These results suggest that PE-cfDNA can complement plasma and tumor genotyping for detecting EGFR variants in patients with advanced NSCLC.

MeSH terms

  • Carcinoma, Non-Small-Cell Lung* / pathology
  • Cell-Free Nucleic Acids* / genetics
  • Drug Resistance, Neoplasm / genetics
  • ErbB Receptors / genetics
  • Female
  • Humans
  • Lung Neoplasms* / diagnosis
  • Lung Neoplasms* / genetics
  • Lung Neoplasms* / pathology
  • Male
  • Mutation
  • Pericardial Effusion* / genetics
  • Prospective Studies
  • Protein Kinase Inhibitors / therapeutic use

Substances

  • Cell-Free Nucleic Acids
  • ErbB Receptors
  • Protein Kinase Inhibitors
  • EGFR protein, human