Molecular Analysis of Endoscopic Cytology Samples Supernatant in Pulmonary Nodules

Lung cancer screening is based on low dose CT scan (LDCT), a highly sensitive but poorly specific tool. Complementary specific approaches are thus strongly needed, among which cell-free DNA (cfDNA) genotyping has been proven highly specific but of low sensitivity (25 to 50% for stage I diseases) due to inconstant tumor shed. Tumor biopsy is thus often required and radial endobronchial ultrasound (rEBUS) bronchoscopy is a minimally invasive approach (\<3% complications) but of limited sensitivity in cases of nodules \< 20 mm. The investigators hypothesized that methylation analysis on cfDNA floating in supernatant derived from rEBUS specimens could improve rEBUS sensitivity

Tumor biopsy is often required to characterize indeterminate nodules. Radial endobronchial ultrasound (rEBUS) bronchoscopy is often used due to a low rate of complications but its sensitivity is limited for small nodules. The investigators hypothesized that methylation analysis on cfDNA floating in supernatant derived from rEBUS specimens could improve rEBUS sensitivity. The primary outcome of this pilot, diagnostic validation, monocentric study is the sensitivity of targeted (9 genes panel) methylation analysis on supernatant cfDNA to detect a malignant nodule. Secondary outcomes include the comparison of supernatant to pathology and plasma cfDNA methylation analysis. Specificity, negative predictive value (NPV), positive predictive value (PPV) of targeted (9 genes panel) methylation analysis on supernatant cfDNA to detect a malignant nodule will be analyzed. 60 patients planned for a rEBUS bronchoscopy for one, two or three \< 20 mm nodule, without mediastinal or extra thoracic lesions (cT1N0M0) will be included. The day of the rEBUS bronchoscopy, 2 7.5 mL blood samples are collected. rEBUS samples' supernatant, usually discarded, is saved. Cell free DNA is extracted from these biological specimens at the Laboratory of Oncological Medical Biology (LBMO) in Toulouse University Cancer Institute and tested for methylation (targeted analysis on 9 genes). The patients will be followed for one year to obtain a final diagnosis and correlate it with tissue, nodule supernatant and plasma methylation analyses.