[Identification of an optimal algorithm for effective diagnostics of non-small cell lung cancer with ALK gene...

The aim of the retrospective part of the study was a) to select an optimal clone of immunohistochemical (IHC) antibody against the ALK protein with specificity and sensitivity high enough to use this antibody as a screening method for selecting non-small cell lung cancer (NSCLC) cases for fluorescence in situ hybridization (FISH) testing of ALK gene rearrangement and b) to determine the diagnostic yield of "small" biopsies i.e. endobronchial, transbronchial and transthoracic biopsies and cytoblocks for ALK gene rearrangement testing. The best IHC method of ALK protein detection (clone D5F3, dilution 1:100, Cell Signaling Technology, Danvers, MA, USA) was then verified in prospective routine testing of patients with NSCLC. ALK status was correlated with tumor morphology and clinical data. In the retrospective part of the study, 170 EGFR-nonmutated cases of NSCLC were IHC and FISH tested. In the prospective part, 557 cases of NSCLC were tested by IHC and 76 by FISH. There were 8/154 (5.2%) cases with ALK gene rearrangement detected in the retrospective part and 24/557(4.3 %) in the prospective part. Sensitivity and specificity of the best IHC method were 100 % and 99 % in the retrospective part and 100 % and 80 % in the prospective part. The diagnostic yield of "small" biopsies was between 74 - 80 % retrospectively, depending on IHC variant, and 88 % prospectively. No case with ALK gene rearrangement detected prospectively had EGFR mutation. A high diagnostic yield confirms that ALK status testing can be used in this type of specimen. A prevalence of 5.2 % in the retrospective part (EGFR-nonmutated cases) and 4.3 % in the prospective part (without known EGFR mutation status), tumor morphology (solid and acinar type, mucinous type or at least partial mucin production (extra- and/or intracellular) as well as lower average age and male/female ratio of patients with ALK positive tumors in the prospective part (57.5 y vs. 65.2 y, 8 men and 16 women vs. 336 men and 197 women) are consistent with global data.