A systematic comparison of pan‐Trk immunohistochemistry assays among multiple cancer types

• Published in: Histopathology 2023-06, Vol.82 (7), p.1003-1012
• Main Authors: Haberecker, Martina, Töpfer, Antonia, Melega, Francesca, Moch, Holger, Pauli, Chantal
• Format: Article
• Language: English
• Subjects: antibody clone; Biomarkers, Tumor - genetics; Cell signaling; Cloning; comparison; false positivity; Humans; Immunohistochemistry; Neoplasms - diagnosis; Neoplasms - drug therapy; Neoplasms - genetics; NTRK‐rearrangement; Oncogene Proteins, Fusion - genetics; pan‐Trk immunohistochemistry; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Receptor, trkA - genetics; Salivary gland; Salivary Gland Neoplasms - pathology; Tumors
• ISSN: 0309-0167; 1365-2559
• DOI: 10.1111/his.14884

Aims NTRK rearranged tumours are rare but can be successfully treated using anti‐TRK‐targeted therapies, making NTRK testing important for treatment choices in patients with advanced cancers. Pan‐Trk immunohistochemistry (IHC) has become a valuable and affordable screening tool in many laboratories. Unfortunately, the choice of antibodies and IHC protocols to investigate biomarkers is not standardised. In this study, we compared the performance of four pan‐Trk IHC methods, using three different clones, primarily in NTRK fusion‐positive tumours. Methods and results We studied the performance of four pan‐Trk IHC methods using three different clones: EPR17341 (Abcam and Ventana), EP1058Y (Abcam) and A7H6R (Cell Signaling) in 22 molecularly confirmed NTRK rearranged tumours. Additionally, selected NTRK fusion‐negative tumours were further included: NTRK mutated (n = 8) and amplified (n = 15) tumours as well as NTRK fusion‐negative tumours driven by other gene fusions, such as ALK, ROS1 and BCOR (n = 20), as well as salivary gland tumours (n = 16). Inter‐rater agreement of three pathologists was additionally calculated, including H‐score. With clone EPR17341 (Abcam in‐house and ready‐to‐use Ventana protocol), all molecularly confirmed NTRK1–3 rearranged tumours were positively detected by immunohistochemistry, while the other clones missed NTRK2–3 rearranged tumours. For the fusion‐negative cohort we found the best performance (least false‐positive cases) using the clone A7H6R (Cell Signalling). Conclusion Given the therapeutic importance, testing for NTRK rearrangements in daily practice has become necessary and, despite IHC being a fast and affordable tool, using it in routine diagnostics is complicated and requires a high level of expertise. A systematic comparison of 4 pan‐Trk IHC assays in a cohort of 22 molecularly confirmed NTRK rearranged and 59 NTRK fusion‐negative tumours with defined molecular profiles, potentially causing false‐positive pan‐Trk staining: a study to better understand sensitivity, specificity and inter‐rater agreement.