A French Multicentric And Prospective Validation Study For Alk Translocation Diagnosis In Lung Adenocarcinomas

8100 Background: ALK rearrangements occur in nearly 5% of NSCLC and lead to a permanent ALK protein activation, targeted by a small molecule, the crizotinib. To date, FISH (Fluorescent In situ Hybridization) is considered as the gold standard to identify ALK abnormalities, but dual testing and pre-screening by immunohistochemistry have been proposed. Methods: The purpose of the study was to compare immunohistochemistry (IHC) using 5A4 and D5F3 Abs, with FISH and quantitative RT-PCR in a series of 500 surgical specimens, collected within one year from 15 French Thoracic Pathology Departments and INCa genetic platforms. Our study was deliberately enriched in ALK positive cases and clinicopathological data were recorded. Results: Among the 459 cases included to date, 340 were both FISH and IHC ALK negative, and 85 were ALK FISH and IHC positive. Fifteen cases were FISH neg/IHC pos, but with low staining scores; 12 cases were FISH pos/IHC neg, most provided by two centers. Seven cases were non interpretable b...