Validation of ROS1 by immunohistochemistry against fluorescent in situ hybridisation on cytology and small biopsy samples in a large teaching hospital

• Published in: Cytopathology (Oxford) Vol. 32; no. 5; pp. 621 - 630
• Main Authors: Narine, Nadira, Wallace, Andrew, Dore, Jonathan, O’Leary‐Jackson, Simon, Al Najjar, Haider, Bailey, Simon, Khan, Kashif, Teng, Benjamin, Qasim, Muhammad, Shelton, David, Holbrook, Miles, Abbasi, Salma, Carter, Matthew, Irion, Luciane, Al‐Habba, Samer, Lindsay, Colin, Blackhall, Fiona, Rana, Durgesh
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2021
• Subjects: Adult; Aged; Aged, 80 and over; Biopsy; Biopsy - methods; Carcinoma, Non-Small-Cell Lung - diagnosis; Carcinoma, Non-Small-Cell Lung - metabolism; cell block; Cellular biology; Chromosome 6; Cytodiagnosis - methods; Cytology; Female; FISH; Fluorescence in situ hybridization; Gene rearrangement; Hospitals, Teaching - methods; Humans; IHC; Immunohistochemistry; Immunohistochemistry - methods; In Situ Hybridization, Fluorescence - methods; Lung Neoplasms - diagnosis; Lung Neoplasms - metabolism; Male; Middle Aged; Next-generation sequencing; Non-small cell lung carcinoma; Patients; Prospective Studies; Protein-tyrosine kinase; Protein-Tyrosine Kinases - metabolism; Proto-Oncogene Proteins - metabolism; ROS1; Small cell lung carcinoma; FISH; biopsy; cytology; IHC; ROS1; cell block
• ISSN: 0956-5507; 1365-2303
• DOI: 10.1111/cyt.12994

Objective Rearranged ROS1, present in 1%‐2% of non‐small cell lung cancer (NSCLC) patients, usually young, never or light smokers, is assessed by fluorescence in situ hybridization (FISH) to determine eligibility for tyrosine kinase inhibitors (TKI). Immunohistochemistry (IHC) for the protein product of ROS1 rearrangement, a cost‐effective alternative, is validated on cytology and small biopsy samples. Methods From 1 March to 31 December 2019, cytology cell blocks and small biopsy samples from a selected cohort of NSCLC patients were concurrently tested for ROS1 gene rearrangement by Vysis 6q22 Break Apart FISH probe and IHC using Cell Signalling D4D6 antibody. Mismatch cases were tested by an RNA fusion next generation sequencing (NGS) panel. Results In a prospective population of 95 cases, 91 were negative and two were positive by both FISH and IHC. Both dual positive cases were female never smokers and benefited from TKI treatment. Another two cases were positive by FISH but negative by IHC and repeat by NGS showed one to be negative but one failed. Turnaround time for IHC was 0 to 8 days from request to authorisation, whilst that of FISH was 9 to 42 days at a cost of £51 and £159 respectively. Conclusion IHC to assess for the protein product of ROS1 gene rearrangement on cytology cell blocks and small biopsy samples in a routine setting is a promising screening method to assess eligibility for TKI treatment with positive and indeterminate cases confirmed by FISH or NGS as it has good negative predictive value, faster turnaround time and is cost effective, with proven technical and clinical validation. This is a prospective evaluation of ROS1 analysis by immunohistochemistry against fluorescence in situ hybridization on cytology and small biopsy samples in a routine diagnostic setting and demonstrates both technical and clinical validation.