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2023 World Conference on Lung Cancer (Posters)
EP06.03. Predicting ROS1 Fusions and Targetable Mu ...
EP06.03. Predicting ROS1 Fusions and Targetable Mutations in Non-small Cell Lung Cancer through H-score Pathological Analysis - PDF(Slides)
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A retrospective study was conducted to optimize the molecular testing approach for non-small cell lung cancer (NSCLC) patients with a positive ROS1 immunohistochemistry (IHC) result. The study aimed to determine the appropriate course of action based on the ROS1 IHC H-score. The study found that an H-score threshold of 150 was highly predictive of ROS1 fusions, with a sensitivity of 100% and specificity of 82.8%. Tumors with an H-score above 150 carried either a ROS1 fusion or an EGFR activating mutation. Additionally, a novel ROS1 TMEM87A fusion was discovered in these tumors. Tumors with an H-score below 150 did not harbor any ROS1 fusions but 83% of them carried a targetable mutation. The study suggests that in high H-score carcinomas, first-line molecular testing should include DNA and RNA explorations, as all ROS1 fusions and EGFR mutations were found in this group. In cases of low H-score, DNA analysis should be prioritized, with RNA analysis as a second-line option if needed. The study also highlights that ROS1 IHC expression is more closely associated with higher ROS1 RNA transcription rather than a lack of specificity of ROS1 antibodies. The findings of this study support the use of the H-score for quantitative staining assessment in ROS1 IHC tumors and provide an algorithm for molecular testing based on specific thresholds.
Asset Subtitle
Ghassen Soussi
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Speaker
Ghassen Soussi
Topic
Pathology & Biomarkers: Genetic Biomarkers
Keywords
retrospective study
molecular testing
non-small cell lung cancer
NSCLC
ROS1 immunohistochemistry
ROS1 IHC H-score
ROS1 fusions
EGFR activating mutation
ROS1 TMEM87A fusion
targetable mutation
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