All-in-one: The dream and reality of molecular cytopathology testing on routine lung cancer smears

Molecular/biomarker testing in lung cytology: A practical approach

The increasing comprehension of molecular mechanisms underlying lung cancer and the discovery of targetable genomic alterations has dramatically change the pathological approach to lung cancer, especially non-small cell lung cancer (NSCLC). This unstoppable knowledge has taken pathologists to the leading front on lung cancer management. This is especially relevant in the world of cytopathology where "doing more with less" is a daily challenge. Nowadays with a growing number of predictive biomarkers needed to manage patients with NSCLC, there has been a paradigm shift in care and handling of diagnostic samples. One of the main emphasis and interest relies on the utilization of cytologic samples and small biopsies for not only diagnostic purposes but also for ancillary testing. Moreover, lung cytopathology is in continuous evolutions with implementation of new diagnostic techniques, new tools, and facing new challenges. The goal of this paper will be to provide the reader with the necessary concepts than can be used to exploit the cytological samples in order to use these samples for comprehensive diagnosis and relevant ancillary testing purposes.

Development and Validation of Molecular Assays for Limited Tissue Samples

As the value of molecular testing of cancer specimens increases, the number of tests imposed on tumor specimens also increases, often in tension with the amount of tumor material available. To develop and validate molecular assays for limited specimens, there are specific concerns that must be addressed, including DNA quality, quantity, and abundance; the number of targets/ability to multiplex; and the analytical sensitivity and specificity of the assay itself. Ultimately, weighing these considerations during assay validation in the overall context of clinical utility and laboratory workflow is critical for delivering the highest level of personalized care to patients.

Idylla assay and next generation sequencing: an integrated EGFR mutational testing algorithm

Aims

Any reference laboratory testing non-small cell lung cancer samples for predictive biomarkers needs to develop and validate a wide range of different molecular techniques, each with a specific time requirement and application. Updated international guidelines suggest that next generation sequencing (NGS) to be the initial procedure. However, in a non-negligible subset of cases, library generation may fail or amplicon coverage may be insufficient. In these NGS ‘invalid’ cases, the Idylla system may represent a viable option for rapid epidermal growth factor receptor (EGFR) genotyping.

Methods

This retrospective study included 68 archival DNA samples previously processed by Ion Torrent NGS assay. Out of these, 43 cases, including 24 EGFR mutant samples, had a valid NGS result, whereas 25/68 (37%) were invalid. All samples were retested by directly pipetting the DNA inside the EGFR Idylla assay cartridge.

Results

In all 43 cases with a valid NGS result, Idylla confirmed the EGFR mutational status. In particular, 24/24 (100%) of EGFR mutant samples as detected by NGS were confirmed by Idylla. Moreover, a large portion of cases (20/25; 80%) whose assessment by NGS was invalid were adequately processed by Idylla. Noteworthy, in 4/25 (16%) of cases, Idylla detected actionable EGFR mutations.

Conclusions

Idylla assay could be very useful to quickly process cases for which NGS does not allow genotyping.