ALK Immunohistochemistry in NSCLC: Discordant Staining Can Impact Patient Treatment Regimen.

INTRODUCTION: Diagnostic immunohistochemistry (IHC) is increasingly accepted as a screening method for anaplastic lymphoma receptor tyrosine kinase gene (ALK) rearrangements in NSCLC. We have sought to establish an ongoing robust external quality assessment process to gauge quality of anaplastic lymphoma kinase (ALK) IHC, which can have an impact on interpretation of patient samples. METHODS: Unstained tissue and cell line samples were distributed on a quarterly basis to participating laboratories from 30 countries. Participants stained the slide using their routine diagnostic ALK IHC method and returned the slide along with their in-house control and methodology details. Slides were assessed by a team of pathologists and scientists. RESULTS: Overall, there was a mean pass rate of 83% (range 71%-98%), with 38 variations in staining protocol. Methods included the following: the Roche D5F3 assay (65% of users, pass rate 93%); Novocastra 5A4 (15% of users, pass rate 65%); Cell Signaling Technology D5F3 (7% of users, pass rate 91%), and Dako ALK1 (5% of users, pass rate 50%). Choice of methodology directly affected final interpretation of distributed ALK-positive and ALK-negative NSCLC cases, which were correctly identified by 89% and 88% of participants, respectively. Antibody detection method was a contributing factor in false-negative staining results. The choice of laboratory controls was found to be unsuitable, and as such, in-house control recommendations are also provided. CONCLUSIONS: ALK IHC is a robust screening technique, but there is concern that some diagnostic laboratories are using inadequate staining methods, which has a direct impact on final interpretation. External assessment helps provide laboratories with continued confidence in their ALK IHC testing.

Improvement in the quality of molecular analysis of EGFR in non-small-cell lung cancer detected by three rounds of external quality assessment.

BACKGROUND: The clinical need to determine the presence of epidermal growth factor receptor (EGFR) gene mutations in non-small-cell lung cancers (NSCLC) in order to make informed decisions for patient treatment has seen the widespread introduction of EGFR molecular testing in many laboratories. To ensure high-quality molecular testing and allow laboratories to externally measure the standard of the service, an external quality assessment (EQA) scheme was provided to assess the whole testing process. METHODS: Formalin-fixed paraffin-embedded NSCLC tumour sections were distributed to laboratories for routine EGFR molecular testing, and the genotyping accuracy, interpretation of the result and clerical accuracy of the report were independently assessed. RESULTS: Three rounds of assessment have identified many genotyping errors and have highlighted the need for external assessment and education in many testing laboratories. The main issues raised were the importance of accurate genotyping, including the use of common mutation nomenclature, clear unambiguous interpretation of the result, the impact of tumour sample assessment regarding amount of tumour being analysed and the heterogeneity of the sample on the molecular test result. CONCLUSIONS: Improvements in all these areas were observed during the progression of the three EQA rounds, however, continuous unacceptably high genotyping error rates demonstrate the clear need for continual external assessment and education in this field.