Accurate identification of ALK positive lung carcinoma patients: novel FDA-cleared automated fluorescence in situ hybridization scanning system and ultrasensitive immunohistochemistry

Background Based on the excellent results of the clinical trials with ALK-inhibitors, the importance of accurately identifying ALK positive lung cancer has never been greater. However, there are increasing number of recent publications addressing discordances between FISH and IHC. The controversy is further fuelled by the different regulatory approvals. This situation prompted us to investigate two ALK IHC antibodies (using a novel ultrasensitive detection-amplification kit) and an automated ALK FISH scanning system (FDA-cleared) in a series of non-small cell lung cancer tumor samples. Methods Forty-seven ALK FISH-positive and 56 ALK FISH-negative NSCLC samples were studied. All specimens were screened for ALK expression by two IHC antibodies (clone 5A4 from Novocastra and clone D5F3 from Ventana) and for ALK rearrangement by FISH (Vysis ALK FISH break-apart kit), which was automatically captured and scored by using Bioview's automated scanning system. Results All positive cases with the IHC antibodies were FISH-positive. There was only one IHC-negative case with both antibodies which showed a FISH-positive result. The overall sensitivity and specificity of the IHC in comparison with FISH were 98% and 100%, respectively. Conclusions The specificity of these ultrasensitive IHC assays may obviate the need for FISH confirmation in positive IHC cases. However, the likelihood of false negative IHC results strengthens the case for FISH testing, at least in some situations.Funding: This work was partially supported by Abbott, Pfizer, Fundación Mutua Madrileña and Fondo de Investigaciones Sanitarias (PI11/02866). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: E. Conde and J. Gómez-Román: honoraria, Pfizer. M. Salido: Advisory Board, Pfizer. E. Arriola: Advisory Board and Research Funding, Pfizer. F. López-Ríos: Advisory Board and Research Funding, Pfizer. Research funding: Abbott and Ventana Medical Systems. Ventana Medical Systems provided reagents free of charge. There are no further patents, products in development or marketed products to declare. This does not alter the authors’ adherence to PLOS ONE policies on sharing data and materials. Acknowledgments F. López-Ríos thanks R. Franklin for her contribution to this work. The authors wish to thank the Tumor Bank at the ‘Laboratorio de Dianas Terapéuticas’, Hospital Universitario Sanchinarro, for handling the samples used in this study, and Dr. Lukas Bubendorf (Basel) for his help with the immunohistochemistry protocols. The excellent technical help of Luna Muñoz is also gratefully acknowledged. Translated into English by Michelle Homden