P1.02-030 Performance Evaluation of ALK/ROS1 Dual Break Apart FISH Probe Kit (RUO) in Non-Small-Cell Lung Cancer

Abstract

ALK and ROS1 gene rearrangements are distinct molecular subsets of non-small-cell lung cancer (NSCLC), and they are strong predictive biomarkers of response to ALK/ROS1 inhibitors, such as crizotinib. Thus, it is clinically important to detect patients who will benefit from such treatment and develop an effective screening strategy. In this study, we aim to evaluate the diagnostic performance of ALK/ROS1 RUO FISH probes which can concurrently detect ALK and ROS1 rearrangements. The study populations were composed of three patient cohorts with histologically confirmed lung adenocarcinoma (ALK rearrangement, ROS1 rearrangement and both wild type). Patient specimens consisted of 12 ALK-positive, 9 ROS1-positive and 21 ALK/ROS1-wild type formalin-fixed paraffin-embedded samples obtained from surgical resection or excisional biopsy. ALK rearrangement status was determined by Vysis LSI Dual Color Break Apart Rearrangement Probe (Abbott Molecular, Abbott Park, IL, USA) and ROS1 rearrangement status was assessed by ZytoLight SPEC ROS1 dual color break apart probe (Zytovision. Bremerhaven, Germany). All specimens were re-evaluated by ALK/ROS1 Break Apart FISH RUO 4-color kit. FISH images were scanned via the BioView Duet and interpreted remotely via BioView SoloWeb. A total of 42 patient samples were evaluated. The concordance of results obtained from ALK/ROS1 Break Apart FISH RUO 4-color kit was evaluated relative to the ALK and ROS1 rearrangement status of the specimen, as previously determined. One ROS1-positive and 2 wild-type samples were excluded from analysis due to high background. Regarding 12 ALK-positive samples, 12 were ALK-positive by ALK/ROS1 RUO FISH, showing 100% (n=12/12) sensitivity to predict ALK rearrangement. Regarding 8 ROS1-positive samples, 6 cases were ROS1-positive by ALK/ROS1 RUO FISH, showing 75% (n=6/8) sensitivity to predict ROS1 rearrangement. Two cases showed weak ROS1 signals that could not be enumerated. Regarding 19 wild type cases, 18 cases were negative by ALK/ROS1 RUO FISH, showing 95% (n=18/19) specificity, while one case showed poor ROS1 signals which could not be properly enumerated. ALK/ROS1 RUO FISH can detect ALK and ROS1 rearrangements simultaneously in NSCLC. The fluorescence of ROS1 signal may be weakened by slide shipment and remote scoring.