ALK Gene Rearrangement Testing in Non-Small Cell Lung Carcinoma by ThinPrep-FISH
Eugen C Minca, Bryce P Portier, Zhen Wang, Jennifer Brainard, Carol Farver, Yan Feng, Patrick C Ma, Valeria Arrossi, Nathan Pennel, Raymond R Tubbs. Cleveland Clinic Foundation, Cleveland, OH
Background: Anaplastic lymphoma kinase (ALK) gene rearrangements in advanced non-small cell lung carcinomas (NSCLC) are an indication for targeted therapy with ALK-specific inhibitors, including crizotinib. ALK rearrangement status is commonly assessed by fluorescence in-situ hybridization (FISH) on formalin-fixed paraffin-embedded (FFPE) samples using the IVD-class FISH system approved by the US FDA as a companion diagnostic tool for crizotinib-based treatment eligibility. Cytologic preparations may represent alternative valuable material in cases of FFPE-FISH failure or unavailability. Here we assessed the feasibility of FISH on ThinPrep samples for detecting ALK rearrangements in a NSCLC case series at our institution.
Design: The study included 40 matched ThinPrep and FFPE samples from patients with advanced NSCLC clinically referred for ALK testing. FISH was performed using the AMV ALK Break Apart FISH Probe Kit (Abbott Molecular, USA). IHC for ALK was performed on FFPE samples with the D5F3 rabbit monoclonal antibody (Cell Signaling Technology) and ultrasensitive OptiView DAB IHC Detection Kit with amplification (Ventana Medical Systems). Statistical analysis was performed using the GraphPad Prism software (GraphPad Software).
Results: ThinPrep-FISH for ALK rearrangements was informative in 39/40 cases: 34 negative (mean 4.8%, median 4%, range 0-12% positive cells), 5 positive (mean 44.4%, median 20%, range 16-88% positive cells). IHC for ALK was informative in 35/40 cases: 30 negative, 5 positive, 100% concordance with ThinPrep-FISH on matched samples. FFPE-FISH was informative in 19/40 cases: 13 negative, 6 positive. 2 discordant positive cases approximated the FFPE-FISH cut-off of 15% positive cells (15% and 18%) and were negative by IHC, in agreement with the ThinPrep-FISH result. Overall, ThinPrep-FISH provided significantly more informative results that FFPE-FISH (97.5% vs 47.5%, p<0.001), 100% concordance with ultrasensitive IHC and 88.8% agreement with FFPE-FISH on a limited number of cases.
Conclusions: ThinPrep-FISH can reliably detect ALK gene rearrangements in cytologic preparations from patients with NSCLC. The high concordance between ThinPrep-FISH with IHC and FFPE-FISH warrants the routine use of ThinPrep-FISH for clinical ALK molecular testing in NSCLC cases with unavailable or limited FFPE material.
Monday, March 4, 2013 1:00 PM
Poster Session II # 283, Monday Afternoon