Abstract
e22042 Background: The outcome of patients with advanced NSCLC with ALK fusions detected by ALK FISH has improved significantly when treated with crizotinib. ALK IHC*, which is a relatively inexpensive assay, correlates well with ALK FISH. An international ALK IHC project was initiated to formulate scoring standardization and assess reproducibility of an ALK IHC assay. Methods: Using ALK FISH status (Abbott, Des Plaines, IL) as the enrollment criteria, formalin-fixed paraffin-embedded tumors from 103 NSCLC patients from 6 different institutes were stained and analyzed for ALK protein expression using a recently developed fully automated ALK IHC assay (Ventana, Tucson, AZ). Seven international observers blindly assessed the specimens as “positive” or “negative” after two training sessions and the use of an assessment manual. Results: The agreement between ALK IHC and ALK FISH for evaluable cases where 4/7 or 6/7 readers agreed on ALK status was 92/98 cases (93.9%, 95%CI 87.3-97.2) and 90/96 cases (93.8%, 95%CI 87.0-97.1) overall; positive IHC agreement was 39/43 cases (90.7%, 95%CI 78.4-96.3) for both methods; negative IHC agreement was 53/55 cases (96.4%, 95%CI 87.7-99.0) and 51/53 cases (96.2%, 95%CI 87.2-99.0), respectively. Average inter-observer agreement was 1987/2032 reads (97.8%, 95%CI 95.9-99.1) overall; average positive agreement was 1,710/1,755 reads (97.4%, 95%CI 95.0-99.1); average negative agreement was 2,264/2,309 reads (98.1%, 95%CI 96.4-99.3). Of the 6 discrepant cases, 4 were unanimously scored as ALK IHC negative with ALK FISH being positive. Two were confirmed by chromogenic ISH to be ALK rearranged, one was unevaluable, and one was genomically heterogeneous. The remaining 2 discrepant cases were discordant among scorers relating to ALK IHC cellular compartment staining in one case and a minute sample size showing ALK IHC staining in the other. Conclusions: ALK IHC standardized assessment achieved high inter-observer reproducibility among an international panel of participants and high correlation with ALK FISH. A screening strategy using ALK IHC should be considered.*ALK IHC has not been approved for use in the US as a diagnostic for crizotinib.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
