Performance of ROS1 fusion gene test using FFPE tissue and bronchoscopic cytologic specimen

Background and Objective: Recently, AmoyDx™RT-PCR Kit has been approved for ROS1 fusion gene (ROS1) test. Formalin-Fixed Paraffin-Embedded tissue (FFPE-t) materials are recommended to test. However, the quality of RNA in FFPE-t is often inadequate. Therefore, we retrospectively analyzed success rate of ROS1 test of non-small cell lung cancer (NSCLC) in clinical practice cases. Patients and Methods: From April 2017 to December 2018, 156 cases of NSCLC were subjected to ROS1 test using FFPE-t (surgical and/or biopsy) or bronchoscopic cytologic specimens. Success rates of each specimen were analyzed. Results: Among 156 cases, one case was positive, 132 cases were negative, and 23 cases were not evaluable. Examination success rate was 133/156(85%). Success rate of surgery specimen was 45/45(100%), and that of bronchoscopic biopsy specimen was 63/83(76%). There ware 25 cases in which ROS1 test were examined using both FFPE-t and cytologic specimens via bronchoscopy. The success rate was 18/25(72%) in FFPE-t and 18/25(72%) in cytologic specimens. The average turn-around-time was significantly shorter in cytologic specimen than that of FFPE-t (8.0 vs. 10.8 days; p<0.05). Conclusion: ROS1 test using FFPE-t specimen from surgery or bronchoscopy was a high success rate. ROS1 test using cytologic specimen via bronchoscopy was equivalent to that using FFPE.