29P The routine detection of ROS1 fusion rearrangement in non-small cell lung cancer

Abstract

Aim/Background: To compare immunohistochemistry (IHC), fluorescent in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (qRT-PCR) in their ability to detect ROS proto-oncogene 1(ROS1) fusion rearrangement in non-small cell lung cancer (NSCLC), and discuss the clinical characteristics and histopathology of the patients with ROS1 rearrangement. Methods: Patients with previously diagnosed NSCLC were included in the study during November 2013 to December 2014 in the First Affiliated Hospital of Guangzhou Medical University. IHC was conducted using the D4D6 monoclonal antibody (mAb) in an automatic IHC instrument, and FISH was conducted on tissue microarrays (TMAs). qRT-PCR was conducted as interpretation, and the positive cases of FISH and qRT-PCR had received direct sequencing. Results: Two hundred and thirteen cases were included in this study. A total of 7 patients harbored an ROS1 rearrangement. The concordant rate of FISH and qRT-PCR was 100%, and FISH and IHC were 100% concordance when IHC showed a diffusely moderate to strong cytoplasmic expression pattern (H-score ≥ 150 or extent and intensity reached 2+). The cases with no or faint IHC expression were negative by FISH and qRT-PCR analysis. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of IHC were 100%, 95.1%, 41.2% and 100%, respectively. The patients with ROS1 rearrangement tended to be females (P = 0.046).Tabled 1H-score and extent and intensity of IHCH-scoreFISH +FISH-SensitivitySpecificity≥ 5075100%50.0%≥10071100%90.0%≥15070100%100%≥2006085.7%100%≥2502028.6%100%Extent & intensity1 +710100%95.1%2 +70100%100%3 +2028.6%100% Open table in a new tab Conclusions: Because of the high sensitivity and specificity of IHC using the D4D6 mAb, IHC can be a reliable and effective method for preliminary screening of ROS1 rearrangements in patients with NSCLC, and the positive criteria should be set at 150 of H-score or 2+ of extent and intensity method. FISH and qRT-PCR should be used to confirm those cases with no or faint stain in IHC. Female patients with adenocarcinoma should receive testing for ROS1 rearrangements because this feature can be found in patients of NSCLC with ROS1 rearrangement. Disclosure: All authors have declared no conflicts of interest.