Molecular Diagnosis of Lung Cancer Via Bronchoscopy: The Significance of Bronchial Liquid Biopsy (ctDNA and ctRNA)

The management of lung cancer is a major public health challenge. Molecular anomaly testing is recommended from the early stages for optimal and personalized care of all lung adenocarcinomas and non-smoker lung cancers. The search for these anomalies relies on increasingly advanced and sensitive analysis techniques, particularly Next-Generation Sequencing (NGS), which can simultaneously detect various molecular abnormalities in both DNA and RNA, including point mutations, complex mutations, rearrangements, and amplifications. These techniques are predominantly performed on biopsy specimens embedded in paraffin. However, these biopsies may require invasive and sometimes iatrogenic procedures, and their feasibility, quantity, and quality of the samples can be limited. The turnaround time for analysis results from the time of biopsy is typically around 2 to 3 weeks. In recent years, alongside the improvement in the sensitivity of molecular analysis techniques, liquid biopsy has emerged as a valuable approach, particularly in the analysis of circulating tumor DNA (ctDNA). ctDNA is a non-invasive diagnostic biomarker that has been validated for detecting targetable molecular anomalies similar to those detected by "conventional" biopsies. ctDNA can be detected in plasma through a simple blood draw, as well as in cerebrospinal fluid, urine, saliva, or any other "liquid" sample from the patient. The concordance between mutations identified in the tumor and those detected in the blood exceeds 90% specificity in numerous studies. However, the sensitivity of ctDNA detection varies depending on the stage of the disease and the sensitivity of the detection technique used. The utility of bronchial ctDNA is currently underexplored. However, there is a rationale for investigating ctDNA as close as possible to the cancerous lesion at the bronchial level. Bronchial ctDNA could play a role in molecular diagnosis for distal lesions not visible through endoscopy and could also help re