52
IASLC ATLAS OF ALK TESTING IN LUNG CANCER
(5A4 by Novocastra or DSF3 by Cell Signaling with ADVANCE detection)
ALK IHC
Negative
(No ALK expression)
Positive
(Any ALK expression)
FISH
ALK negative ALK positive
Figure 5. Algorithm for diagnostic screening for ALK testing with IHC and FISH used for confirmation. Modified, with permission from, Conklin C, Craddock KJ, Have C, et al. Immunohistochemistry is a reliable screening tool for identification of ALK rearrangement in non-small-cell lung carcinoma and is antibody dependent. J Thorac Oncol. 2013;8(1):45-51.
(adenocarcinoma, large cell carcinoma, mixed tumors with adenocarcinoma, NOS)
NSCLC
ALK IHC
1-2 working days
Negative
Positive
FISH test
2-3 working days
Negative
No ALK rearrangement
Positive
ALK rearrangement
Figure 6. Possible ALK testing algorithms in NSCLC proposed by the Italian Association of Medical Oncology and the Italian Society of Pathology and Cytopathology. Dotted boxes and dotted lines correspond to hypothetical ways to select tumors for FISH after screening with IHC. The length of time needed for testing and interpretation of results of IHC and FISH are noted. NOS=not otherwise specified. Modified, with permission, from Marchetti A, Ardizzoni A, Papotti M et al. Recommendations for the analysis of ALK gene rearrangements in non-small-cell lung cancer: a consensus of the Italian Association of Medical Oncology and the Italian Society of Pathology and Cytopathology. J Thorac Oncol. 2013;8(3):352-358.
Conclusion
Screening for ALK with IHC is recommended in most regions because of its cost-effectiveness for mass screening and its verification of ALK-positive results by FISH. However, IHC needs further clinical validation with demonstration of strong correlation with response to ALK tyrosine kinases inhibitors. In addition, FISH must continue to be evaluated, to determine the clinical importance of results that are currently interpreted as atypical or borderline. Several diagnostic algorithims for ALK testing have been proposed.