137IN - Importance of External Quality Assessement in Immuno-Oncology

Abstract

Listen

Translate article

ABSTRACT The important role of immunohistochemistry (IHC) is well known. IHC will recognize antigens and, consequently, identify and classify specific cells within a cell population whose morphology is heterogenous or apparently homogenous. Since many years external quality assessment (EQA) schemes for IHC are organized by NORDIQC and UK NEAQS. Since some years, IHC can be used for treatment selection in advanced NSCLC. In 2012, the European Society of Pathology (ESP) proposed an EQA scheme to promote high quality biomarker testing in NSCLC for EGFR mutation analysis and ALK rearrangement detection (IHC, FISH). From 2014 on, ROS1 testing is also included. The scheme aims to assess and improve the current status of testing in NSCLC, to provide education and remedial measures, to permit inter-laboratory comparison and to allow validation of test methods by distributing validated material harboring well-defined aberrations. In total, 173 different laboratories participated in the pilot rounds. In the first round, 29 laboratories submitted results for ALK IHC. In the second round, 58 laboratories submitted results for ALK IHC. If carefully clinically validated according to ISO 15189, ALK IHC may be considered as a screening method to select specimens for ALK FISH testing. In the context that at the time of the pilot studies no interlaboratory comparison validation studies were available, ALK IHC performance from our study shows that IHC testing is well implemented. Not surprisingly however, the error rates for IHC were greater than for FISH. Our study demonstrates improvement of ALK testing after only two rounds. It is expected that larger datasets, spanning a larger number of EQA participations will demonstrate a statistically significant improvement in performance. On scheme level, the decreased error rates in the second round demonstrated improvement for both ALK FISH and ALK IHC. Error rates for ALK FISH TMA and ALK IHC were still high (>5%), which stresses the need for continued education through EQA. Based on the results from this study, recommendations for the methodology, analysis, interpretation and result reporting were issued. External quality assessment is a crucial element to improve the quality of molecular testing. Disclosure: All authors have declared no conflicts of interest.