SESSION TITLE: EBUS and Lung Cancer
SESSION TYPE: Original Investigation Slide
PRESENTED ON: Sunday, October 27, 2013 at 03:00 PM - 04:00 PM
PURPOSE: The detection of EGFR-gene mutation status and ALK-gene rearrangements in non-small cell lung cancer(NSCLC) are important as they can direct therapy towards specific inhibitor therapy. The ability to reliably perform genetic testing on tissue procured through minimally invasive means is essential given the widespread adoption of EBUS-FNA. Current testing methods for EGFR and ALK require formalin-fixed paraffin-embedded(FFPE) tissue, which typically require larger amounts of tissue that can be acquired through standard EBUS-FNA techniques. It was proposed at our institution to perform EGFR and ALK testing on alcohol-based cytology specimens (cytology cell block or FNA pellet for EGFR, ThinPrep for ALK) rather than FFPE specimens since these typically require less tissue. Additionally it was felt that DNA preservation, critical for FISH testing, would be superior in non-formalin preservative. We present the validation of these novel methods on FNA samples in a NSCLC case series at our institution.
METHODS: Our study included all FNA samples from patients with NSCLC requiring testing for EGFR mutation (100 samples) and/or ALK rearrangement (40 samples). The EGFR group composed of 44 FFPE biopsies, 17 cytology cell blocks, and 39 FNA pellets in which in-house allele specific-polymerase chain reaction (AS-PCR) was performed for detection of EGFR mutations, and compared to external testing at a CLIA-accredited reference lab. The ALK group consisted of 40 matched ThinPrep and FFPE samples, and were analyzed using fluorescence in-situ hybridization (FISH) for ALK rearrangement detection, and confirmed with ultrasensitive immunohistochemistry(IHC).
RESULTS: The FNA-based EGFR AS-PCR assay had a 98% concordance with external testing; there was ample tissue for analysis in all specmens. ThinPrep-FISH for ALK rearrangements yielded a result in 39/40(97.5%) cases, FFPE-FISH in 19/40(47.5%) cases. Overall, ThinPrep-FISH provided significantly more informative results than FFPE-FISH (p<0.001), and had 100% concordance with ultrasensitive-IHC.
CONCLUSIONS: Using our novel methodology, FNA-based tissue can be reliably used to detect EGFR-gene mutations and ALK-gene rearrangements from patients with NSCLC. Additionally, ThinPrep-FISH was more informative than FFPE-FISH for ALK-gene rearrangement detection.
CLINICAL IMPLICATIONS: These results support the adoption of these novel methods for EGFR and ALK testing from FNA samples. Further study using these methods on samples procured solely from EBUS-TBNA is warranted.
DISCLOSURE: The following authors have nothing to disclose: Joseph Cicenia, Eugen Minca, Francisco Almeida, Thomas Gildea, Michael Machuzak, Sonali Sethi, Jennifer Brainard, Raymond Tubbs
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