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

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.

Droplet digital PCR of tumor suppressor gene methylation in serial oral rinses of patients with head and neck squamous cell carcinoma.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) currently lacks sensitive approaches to detect cancer-related traits in body fluid. METHODS: Methylation of tumor suppressor genes (TSGs) (PAX5, EDNRB, and DCC) were measured in the oral rinses from 50 HNSCC and 58 control subjects using droplet digital PCR (ddPCR). Diagnostic accuracies in detecting HNSCC and the detection rate of recurrence in the post-treatment monitoring were analyzed. RESULTS: ddPCR TSG methylation detection in oral rinses for diagnosis of HNSCC had an AUC of 0.892 for PAX5, 0.753 for EDNRB, and 0.729 for DCC. Significant drop of TSG methylation was observed after completion of surgery (p < 0.01). 76.9% of the relapse cases had a pre-emptive rebound of methylation above presurgery levels in at least one of the tested markers before confirmed recurrence. CONCLUSIONS: Utilizing ddPCR for TSG methylation detection in oral rinses shows potential for detection and monitoring of HNSCC.

Clinical utility of circulating Epstein-Barr virus DNA analysis for the management of nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is one of the commonest cancers in Southern China. The carcinogenesis is closely associated with Epstein-Barr virus (EBV) infection. In endemic regions with high incidence of NPC, EBV genome can be detected in virtually all NPC tumor tissues. Over the last decade, circulating cell-free EBV DNA has been developed as a tumor marker for NPC. Plasma EBV DNA analysis using real-time PCR has been shown to be useful for early detection, prognostication and monitoring of treatment response of NPC. In this review, the clinical applications of EBV DNA analysis in the management of NPC would be discussed.