Testing EGFR with Idylla on Cytological Specimens of Lung Cancer: A Review

Abstract

The current standard of care for advanced non-small-cell lung cancer is based on detecting actionable mutations that can benefit from targeted therapy. Comprehensive genetic tests can have long turn-around times, and because EGFR mutations are the most prevalent actionable mutation, a quick detection would enable a prompt initiation of targeted therapy. Furthermore, the scarcity of diagnostic material means that sometimes only cytologic material is available. The Idylla™ EGFR assay is a real-time PCR–based method able to detect 51 EGFR mutations in 2.5 h. Idylla is validated for use only on FFPE sections, but some researchers described their experiences with cytological material. We reviewed the relevant literature, finding four articles describing 471 cases and many types of cytological input material: smears, cell-block sections, suspensions, and extracted DNA. The sensitivity, specificity, and limit of detection appear comparable to those obtained with histological input material, with one exception: the usage of scraped stained smears as input may reduce the accuracy of the test. In conclusion, usage of cytological material as input to the Idylla EGFR test is possible. A workflow where common mutations are tested first and fast, leaving rarer mutations for subsequent comprehensive profiling, seems the most effective approach.

Assessing and Evaluating the Scope and Constraints of Idylla Molecular Assays by Using Different Source Materials in Routine Diagnostic Settings

“…For each IVD molecular assay, the average Cq values from multiple case samples with FFPE material were akin to the reference Cq value (manufacturer’s recommendation). This is in line with previous studies showing the concordance and specificity of different assays included in our study [ 6 , 14 , 15 , 16 ]. Contrary to expectations, this study did not find a significant difference between the performance of the assays from sample types C and D (DNA isolated from FFPE tissue and HE-stained slides), showing an overall >91% sensitivity performance.…”

“…The reason for this is not clear, but it may have something to do with the NRAS-BRAF assay itself being designed very stringent in which the quality of the sample is of utmost importance or increased DNA fragmentation in NRAS and BRAF loci [ 19 ]. In addition, this could be due to high background issues and heterogeneity, which are often associated with cytological specimens, including HE-stained tissue material [ 14 , 20 ]. However, when the raw curves were observed for case samples #6, #7, #8 and #10, the mutations to be identified were present with very high Cq values of more than 42.…”

Diagnosis of Langerhans cell histiocytosis on cytological examination of cerebrospinal fluid: Report of the first case

“…9,10 Cytology is a versatile tool which can be used to obtain material both to render a diagnosis and to perform further studies. 11,12 Fineneedle aspiration cytology can sample many lesions, both superficial and deep, with good diagnostic performance and minimal costs and invasiveness. 13,14 The obtained material can be used for special techniques such as immunocytochemistry, flow cytometry, and molecular analyses.…”

Overview and update on molecular testing in non‐small cell lung carcinoma utilizing endobronchial ultrasound‐guided transbronchial needle aspiration (EBUS‐TBNA) samples

“…17 Some studies comparing scraping cells from slides and the use of cell blocks showed similar high sensitivity rates with both techniques, but other studies found that cell scraping may reduce the accuracy of PCR-based tests. 21,26 In a previous report by Molina-Vila et al, the authors performed PCR in cytological samples and found a 100% sensitivity rate for detecting in-frame deletions in exon 19, L858R point mutations in exon 21 and the T790 mutation in exon 20, as compared with direct sequencing. 27 Fukui et al compared high resolution melting analysis (HRMA, a PCR-based method) with DNA sequencing in cytological and histological samples, and observed that the analyses of the first PCR products in cytological slides yielded better results than the analyses of biopsy specimens, regardless of the amount of tumor cells examined.…”