Chapter 6
Comparison of Different Assay Platforms for ALK Testing
By Sylvie Lantuéjoul, Marileila Varella-Garcia, Erik Thunnissen, and Yasushi Yatabe
As noted earlier, FISH has been universally accepted as a reference standard in the assessment of ALK rearrangement, and it has been clinically validated and approved for testing to select patients for treatment with an ALK inhibitor (crizotinib). FISH can detect ALK rearrangement regardless of the gene partner and variant and can be performed on archived FFPE specimens. However, FISH requires a minimum of 50 tumor cells, and this requirement may be the reason FISH cannot be used in as many as 20% of lung cancer biopsies (Camidge 2010, McLeer-Florin 2012). FISH has many other limitations; it is time-consuming, has a high cost, requires a fluorescent microscope, and necessitates specialized training for interpretation of results. Because of its limitations, FISH is not available in all routine pathology laboratories, and other assay platforms have been evaluated for their usefulness in detecting ALK in NSCLC. Studies have focused on comparing FISH with IHC with use of various antibodies, multiplex and quantitative RT-PCR, and CISH. IHC may, in theory, detect all ALK fusion proteins, but some variants and fusion partners may generate low protein levels that may be difficult to detect. Therefore, many IHC assays now include an amplification process to enhance the protein signal. IHC remains the most popular and costeffective platform because it • Is used in pathology laboratories worldwide • Can be used on routinely prepared FFPE specimens • Is relatively inexpensive • Requires limited equipment • Offers rapid training and optimization • Usually requires a small number of tumor cells to detect the presence of the fusion protein Although correlation of results of ALK IHC and ALK FISH is excellent, IHC as a pr YX?]?HX\??\??? ?\???H ?S?[?X?]? \?\ H\????Y[? ?[Y]Y[?\??H ]Y[???? ?R?[ ???\???\?X? H[[?? ?]H HS? ?X\??[??[Y[? [? ??YH?[ ?K[?Y?]]?H[??[ ?K\??]]?H ?\?[ ?
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