2022 World Conference on Lung Cancer (ePosters)-EP11.01-007. Tracking ROS1 Fusions in NSCLC - Mirage or Truth When Screening the Desert

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In this study, the researchers aimed to determine the presence of ROS1 fusions in non-small cell lung cancer (NSCLC) and evaluate the accuracy of current detection methods. They analyzed two large cohorts of resected NSCLC patients and used tissue microarray, immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and gene expression techniques to detect ROS1 fusions.<br /><br />The results showed that the occurrence of ROS1 fusions in resected NSCLC was very low. FISH detected ROS1 fusion in only 2 out of 630 cases (0.3%). However, there were also 8 cases with ambiguous FISH results that were considered negative.<br /><br />IHC assays using different antibody clones showed varying accuracy in detecting ROS1 fusion. The D4D6 clone detected positive protein expression in 24 out of 665 cases (3.6%), while the SP384 clone detected positive expression in 18 out of 639 cases (2.8%). The EPMGHR2 clone detected positive expression in only 1 out of 592 cases (0.2%).<br /><br />Gene expression analysis using RNA sequencing and microarray techniques showed elevated RNA levels in 19 out of 369 cases (5.1%), suggesting the presence of ROS1 fusions.<br /><br />The researchers also used a NanoString fusion assay to confirm the presence of ROS1 fusion. Only one case that showed consistent positive results in FISH and IHC was found to be truly rearranged. Other cases with high protein or RNA expression or ambiguous FISH results did not show any indication of gene fusion in the NanoString assay.<br /><br />Overall, the frequency of ROS1 fusions in this study was lower than previously presumed, with a prevalence of 0.2% in the two large Swedish cohorts analyzed.<br /><br />Based on these findings, the researchers concluded that IHC protocols are suitable for screening ROS1 fusions, but transcript-based assays are preferable for validation in clinical diagnostics.

Asset Subtitle

Johanna Mattsson

Meta Tag

Speaker Johanna Mattsson

Topic Pathology - Genomics & Analytics

Keywords

ROS1 fusions

non-small cell lung cancer

NSCLC

detection methods

tissue microarray

immunohistochemistry

fluorescence in situ hybridization

gene expression techniques

FISH results

IHC assays