Molecular profiling and utility of cell-free DNA in nonsmall carcinoma of the lung

BACKGROUND: Lung carcinoma accounts to the most common cause of cancer globally. Optimal management of nonsmall cell lung carcinoma (NSCLC) requires prognostic biomarkers that help in targeted therapy and identification of tumor subsets with a distinctive molecular profile that can foretell response to therapy. Quantitative analysis of circulating cell-free DNA is considered as a possible aid for lung cancer screening. AIMS AND OBJECTIVES: The main aim of our study was detection of the clinicopathological spectrum of NSCLC, immunohistochemical (IHC) study of lung adenocarcinoma with epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), and molecular expression of EGFR mutation using Formalin fixed paraffin embedded tissue (FFPE) and cell-free DNA (cfDNA) from blood samples. MATERIALS AND METHODS: It was a prospective and observational study conducted in the Department of Pathology in association with the Department of Chest Medicine in a tertiary care hospital for 18 months, done on 50 patients. Histological subtyping of lung carcinomas was done, followed by IHC analysis using P40, thyroid transcription factor (TTF1), EGFR, and ALK. Molecular analysis for EGFR mutation was done using FFPE and cfDNA from the patient's blood samples. RESULTS AND ANALYSIS: On histological subtyping, majority (66%) of the cases were found to be adenocarcinoma. All adenocarcinoma (66%) cases show TTF1 positivity and all squamous cell carcinoma (32%) cases show P40 positivity. All the ALK-positive (6%) cases were never smokers and histologically diagnosed as adenocarcinoma. About 58% of the NSCLC cases were found to be EGFR IHC positive. Formalin-fixed paraffin tissue (FFPE) showed EGFR mutation in 32% cases, of which majority were deletion (19, 28%) and rest (4%) of the cases involving mutation in exon 21. From cfDNA, mutations were noticed in 16% of the cases where majority involved deletion 19 (12%), whereas the rest of the cases were positive for missense mutation in exon 21 of the EGFR gene (2%) and compound heterozygous mutation involving deletion 19 and missense mutation for exon 21 (2%). On correlation of EGFR mutation studies from FFPE with that of cfDNA analysis, the study was statistically significant (P = 0.000). CONCLUSION: This study reports clinicopathological, immunochemical, and molecular analysis of EGFR among NSCLC cases. EGFR mutation detection from cfDNA has its advantage of being a noninvasive technique to avoid rebiopsy in cases of the progressive disease to detect resistance to a drug and emergence of a newer mutation. Mutation detection from FFPE samples still remains the gold standard for targeted therapy using EGFR tyrosine kinase inhibitors. ALK rearrangement detection using IHC serves as an adjunct to EGFR diagnosis.