WCLC 2025 - Posters & ePosters-EP.06.48 Complementary Role of IHC in ALK Fusion Detection: A Validation Study of NSCLC NGS-Based Screening in Seven Laboratories

EP.06.48 Complementary Role of IHC in ALK Fusion Detection: A Validation Study of NSCLC NGS-Based Screening in Seven Laboratories

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This multicenter study in Catalonia, Spain, evaluated the complementary role of immunohistochemistry (IHC) in confirming ALK gene fusions detected by next-generation sequencing (NGS) in non-small cell lung cancer (NSCLC) patients. NGS is the standard tool for biomarker testing in NSCLC, including gene fusions like ALK, but technical challenges and low incidence of some fusions complicate detection and assay validation. The study analyzed 1,910 NSCLC samples from seven reference centers in 2022. Among these, 34 cases (1.8%) were ALK-positive by NGS, 990 were negative (51.8%), and 48 were non-assessable (2.5%). Of the negative cases, 553 had enough tissue for retesting by IHC using the VENTANA anti-ALK (D5F3) antibody to verify NGS results.<br /><br />Only two out of 553 IHC retests showed discordant results, both initially tested negative by the Thermo Fisher Oncomine Comprehensive Assay, an RNA-based amplicon panel without alternative fusion analysis like ALK expression imbalance scoring. Further analysis by fluorescence in situ hybridization (FISH) confirmed ALK positivity in these two samples, indicating a false negative rate of 0.4% for NGS testing in this cohort. Different NGS methodologies were used across centers, with one center employing DNA-based hybrid-capture sequencing and others relying on RNA amplicon panels.<br /><br />The findings demonstrate that ALK fusion detection by NGS is reliable despite methodological variations, but implementing NGS panels that include alternative fusion detection improves sensitivity. IHC remains a valuable confirmatory tool for negative NGS results when clinical or histological suspicion for ALK rearrangement exists. This complementary approach minimizes false negatives, guiding appropriate targeted therapy in NSCLC patients.

Asset Subtitle

Sergi Clavé

Meta Tag

Speaker Sergi Clavé

Topic Pathology and Biomarkers

Keywords

ALK gene fusion

non-small cell lung cancer

next-generation sequencing

immunohistochemistry

fluorescence in situ hybridization

false negative rate

RNA-based amplicon panel

DNA-based hybrid-capture sequencing

VENTANA anti-ALK (D5F3) antibody

targeted therapy