2022 World Conference on Lung Cancer (Posters)-P2.07-02. RET Fusion Testing with FISH and Real-Time PCR: a Comparison with RNA-Based Next-Generation Sequencing in RET Positive NSCLC

P2.07-02. RET Fusion Testing with FISH and Real-Time PCR: a Comparison with RNA-Based Next-Generation Sequencing in RET Positive NSCLC

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Next-generation sequencing (NGS) is the preferred method for lung cancer biomarker testing, but single-gene assays are still used. This study aimed to compare the performance of fluorescence in situ hybridization (FISH) and real-time PCR assays in detecting RET fusion-positive non-small cell lung carcinoma (NSCLC). The study included 35 tumors, and all four assays analyzed were successful. The NGS results showed the presence of signet ring cells and psammomatous calcifications in a significant percentage of tumors. Out of the 35 NGS-positive samples, 33 were also positive for real-time PCR or FISH. However, there were two false-negative results, each from a different assay. The two RET fusions not identified by real-time PCR were AKAP13-RET and KIF5B-RET. The FISH assays showed a high number of positive tumor cells in these cases. The FISH-positive cases had similar results for both probes, with most tumors showing a typical split pattern. Interestingly, one probe had a higher number of cases with narrow split FISH signals. Two FISH-negative samples contained the KIF5B-RET variant but showed very subtle split images. The study involved multiple hospitals across Spain, and the techniques used were performed according to the manufacturers' recommendations or established criteria. The likelihood of false-negative results with real-time PCR assays may be influenced by the molecular epidemiology of RET fusions in the population. One novel observation was the occurrence of false-negative results with the most frequent fusion partner, KIF5B. The two RET FISH assays used appeared to be interchangeable, but there might be probe-specific interpretation challenges. The study was primarily funded by Lilly and received support from other organizations.

Asset Subtitle

Susana Hernandez, Spain

Meta Tag

Speaker Susana Hernandez, Spain

Topic Pathology - Tumour Genomics

Keywords

Next-generation sequencing

lung cancer biomarker testing

fluorescence in situ hybridization

FISH

real-time PCR assays

RET fusion-positive

signet ring cells

psammomatous calcifications

molecular epidemiology

false-negative results