44P Protecting supernatant cfRNA from cytology samples for the detection of fusions in advanced non-small cell lung cancer (NSCLC) patients

Supernatant from cytological samples, including body cavity effusion, sputum, bronchoalveolar lavage fluid (BALF) and needle aspiration, which has been validated for detecting genetic alternations based on cell free DNA (cfDNA) in patients with non-small cell lung cancer (NSCLC). But the sensitivity of fusions variations test is still problematic. And crucial technique is to protect and obtain stable cell free RNA (cfRNA) for genotyping. This study provided a solution to protect supernatant cfRNA from various cytological samples, and established a reliable protocol to detect gene changes using both cfDNA and cfRNA simultaneously. 111 cytological samples were assessed to estimate the efficiency of cfRNA protective solution by cycle threshold (CT) values of RT-qPCR. An additional set of cytological samples (eg, malignant pleural effusion, sputum, BALF, needle aspiration) diagnosed with cancerous cells and matched tumor samples, were collected from 84 NSCLC patients. The clinical performance of supernatant cfDNA and cfRNA in detecting driver gene mutations was validated using the Multi-Gene Mutations Detection Kit by Amoy Diagnostics. 91.89% (102/111) cfRNA were protected effectively, by estimating their CT values. In the 84 NSCLC patient samples, seven cytological samples failed the tests. Compared with tumor samples, the overall sensitivity and specificity of supernatant cfDNA and cfRNA in detection driver genes were 93.75% (74/77) and 100% (77/77), respectively. When the analysis was limited to patients with fusion gene changes, the sensitivity and specificity were both 100% (11/11) for EML4-ALK, ROS1, RET fusions, and MET gene 14 exon skipping. These results suggest that the improved method enables the detection of mutations and fusions using cfDNA and cfRNA derived from supernatant samples of cytology. This finding is particularly relevant for fusion testing in NSCLC.